I think this test would greatly benefit from testing with only new rotors, and with only rotors with the same design. I've tried several brands of rotors a decade ago and there were huge difference between some brake design, even in the same alloy.
for ebikes, brakes seem to generally be undersized - not taking into account the higher mass of the bike and larger rotational mass of the usually fat tires. would be interesting to see what kind of temps they see when braking to a stop from 30mph. and how that is impacted by thicker rotors at the same diameter vs a larger diameter rotor of about the same mass as the thicker upgrade one. assuming a thicker one fits in the test bike. it's too bad rotors aren't forced to be sold with a wattage rating of how much they can peak absorb and how much they can constantly absorb at room temp. then you could estimate if it's good enough for your use fairly directly.
Yeah that would be cool. Most people wouldn't know how many braking watts they achieve, but it's easy to calculate ((change in kinetic energy - rolling resistance - aerodynamic drag)/braking time). Saying that though heat accumulation in the brakes is more than one-off change in speed -- depends a lot on how the rider is dragging the brakes through the ride, which varies on the trail, the rider, and how purposeful they are with their braking
@@mtbphd I'm thinking two variables that may matter is how fast can the rotor return to safe temp from say 120c while spinning at like 15mph. and how fast does it heat up to 120c using some kind of iso standard brake process. with an ebike a few ounces isn't going to matter .. so i wouldn't mind adding some to have better brakes. it sounds to me like going bigger is better... and go as thick as your calipers can handle
@@mtbphd Is it really that crucial? Isn't it more about maximizing the average heat transfer capability? (Function of rotors' surface and some coefficient related to the speed and airflow around the material) Thicker rotors increase heat capacity, i.e. let the rotor absorb more heat before fading occurs, but I guess that impact on the surface that dissipates the heat is negligible. On the other hand, heat dissipation speed is proportional to the difference of temperatures so the thicker one may be dissipating the same energy at a slower rate due to lower gradient of temperatures? In the context of heat buildup isn't the elevation change of the trail a dominating factor? Braking from 40km/h down to full stop transfers into heat energy equal to slightly over 12m of elevation change (yes, I'm ignoring here the aero drag). That seems like nothing compared to the difference of potential energies between the start and the end of a downhill trail. Assuming that rolling resistance is negligibly small compared to the braking power or aero drag on faster sections, I bet that required heat dissipation speed could be approximated with a function of inclination, average speed, mass and aero drag coefficient (maybe also some coefficient describing the impact of the airflow on the cooling speed of the brake). Therefore, it seems like the optimal strategy for minimizing the heat buildup in rotos is to brake as short and as intensive as possible (the shorter braking times, the higher braking power and higher temperature gradient; the more and faster the rider goes, the smaller energy to dissipate in brakes due to aero drag) with the rotor that has enough, but not much more heat capacity, to stay within a planned temperature limit for a given trail?
I've always loved the feel i get from 203mm rotors, both front and back and never gone smaller diameters again. Haven't had any fading situation with the brakes with different brake systems (shimano, sram and now hopes) with the 203s. Loving your rational take on the subject. Have a nice day!
If you were actually interested in a scientific or engineering test of the effect of rotor thickness on braking...this is the LAST way you would do it. Experts generally start with tests under controlled conditions that evaluate something specific; in this case, for example, there seems to be a hypothesis that a thicker rotor will store more heat and therefore temperatures will climb more slowly under braking. Great! Put together a setup that puts the same braking force into rotors of different thicknesses, and measure the temperature over time with an IR thermometer or embedded thermocouple. You could add realistic amounts of airflow, if you like, but the key factor would be isolating the factor you are interested in and reducing or eliminating the effects of confounding variables/factors, and doing an objective measurement that tests your hypothesis. What does "MTB PhD" do? On-trail testing with every possible confounding factor included, with a sample size of two tests per rotor thickness (!). He concedes that there is a wear difference between the thin and thick rotors (oops!), but neglects all the complex factors in his psychology and technique that could produce different results. He also doesn't have any kind of objective way to evaluate differences, beyond the "feel" or how he behaviorally braked. Did heat storage affect the effectiveness of his brakes? He literally can't tell you. Real-world testing only works when you have a large enough sample to isolate the variable you're interested in from all those other confounding factors. In this case you'd need both an objective measurement and likely tens of attempts from 40-50 different riders. Needless to say, this "test" isn't even close to the statistical power you'd need to make any kind of reliable conclusion. To be fair to "MTB Phd" he's hardly the only one putting meaningless tests out there as "science." Pretty much everything GCN labels as "science" suffers from the same flaws and is just as meaningless. You would just hope that somebody who sold themselves with research credentials would not jettison everything they learned doing that research when they started recording for TH-cam. And "with REAL Proof"? That's just clickbait snake oil.
Harsh, but true. For statistical power, you need to either eliminate or account for confounding factors. And the way this is reported is a point estimate in the difference in heat dissipation among rotors with a confidence interval at a given confidence level.
I work in automotive testing. I'm curious if you've ever experimented with DGPS systems such as OxTS or RaceLogic for any of your data collection. I suspect that signals from the IMUs involved would be too noisy to be useful with mountain biking, but I don't know of anybody who has actually tried it. Have you looked in to anything like that?
Oh nice, are IMUs handy for you? I used IMUs back in 2014/15 continuing some of Paul Macdermids work on vibration exposure in MTB but haven't looked at that kind of data since. The BYB and AiM loggers have accelerometers and gyros. I think a few guys look at the data at the world cups.
On my 130mm trail bike with 203/180mm with 1.8mm thickness, on my 160mm enduro 203/180mm with 2mm. Besides thinkness also pad compound trail uses organic/resin, enduro was sinstered now ceramic
What calipers are you using on both of these bikes? I have Shimano's on my trail hardtail (Deore 2 piston) and enduro bike (SLX 4 piston), running 1.8mm Galfers 203mm front and 180mm rear rotors. Stopping power isn't an issue with either. I wanted to move up to 2mm thick, but I don't think there's enough clearance, unless you're using used/slightly used pads. New pads I don't think it's happening, and I don't feel like buying 2mm rotors just to test that. What do you think @mtbphd?
I agree, i went from shimano to magura rotors and have never gone back...thicker rotors allow faster brake pad engagement...givng me more immediate feedback and confidence
Pad clearance or engagement speed as you put it are not controlled by the rotor thickness. The square edge seal inside the caliper and the fluid viscosity is what controls this. What you did was simply put a thicker rotor in without resetting the pistons and found you have less clearance. This will reset itself after a few rides as the pads wear and will feel identical to the previous rotor.
@@darrylduck6356Exactly what I was thinking. But not sure if viscosity would come into it (unless insanely thick fluid was use for some reason) as that would only affect flow, not pressure on the pistons. Also the seals are so small that I'd think the pad springs would have the main influence on retraction.
Speaking from car experience, more mass means more heat asorbtion. But, one thing to keep in mind is heat dissipation. Larger diameter means more surface area. Which in turn will give faster heat dissipation. When it comes to brakes, you want the mass increase from diameter. Leverage, surface area and mass.
I've had 9 months experience riding a fast e-scooter and ive found that a thinner rotor not only dissipates heat faster, with the right blend of stainless steel and alloy... much like Shimano's ICE rotor. But the 140mm 6-bolt im currently using is significantly lighter and suprisingly doesnt need realigning after every 40 k ride on 30°C + days.
3x spoke lacing is the strongest because the spokes are the most tangent to the hub. It also has leading and trailing spokes so that there are always spokes in tension. I don't see much of that thinking in some of these rotors -- is the force distribution that different, or are they just making pretty patterns and assuming that the steel is more than strong enough?
Good point and good question. I believe rotor design patterns are just about fashion. As long as they don't fold under the heaviest of braking, they're fine (and I've seen this happen twice - once last week with an off brand, and once with a pre-production rotor from a very well known brand). One difference with wheels that is worth pointing out is that there isn't much side-to-side flex in rotors. However some frames aren't stiff enough and allow the hubs to flex under heavy cornering - we can measure this with the BrakeAce Scientific sensor (plus some pros rub holes in their frames with the rotor edges)
Hey Brutha. I received the Ali express 2.3 203 rotors. One of them has a very fine scratch on one side of the braking surface. Do you think I should ask for a replacement? Or will it not be noticeable once bedded? Thanks
Nice! Your only chance to ask for a replacement would be before you use it, so I'd probably try to get that now instead of seeing what happens. (Even though I don't know what will happen!)
I think I will just try the one that’s scratched. Then if it is noticeable I’ll buy another. Wish they had 22m. The machining is not as course as Galfer (my preference) but courser than sram (shiny = grabby from my experience). Anyways I won’t be on my DH bike for 18 months so I’ll probably forget about the wcratch
Good question. I don't know but hopefully someone here will. Unfortunately most manufacturers will simply say that their calipers were designed to be used with their rotors, so not sure if you'll get any real answers from them.
Yeah, that was pretty much what I thought, depends. I really like this idea for a couple reasons, I am a larger rider that rides hard and an ebike rider that is using 160mm rotors and to feel safer need better brakes. Thanks again for the research you presented! @@mtbphd
As long as they physically clear the caliper I can't see why they wouldn't as the pistons will still move within their defined range, just with a starting point slightly further apart. I can't see how this would be any different than varying pad thickness. That said, you should plan on a brake bleed/piston cleaning when you go with thicker rotors.
I'm curious on what do you think the effect is on caliper pad to rotor clearance? I use MT7 myself and the pad clearance on that caliper is nuts u don't even see light coming out of it. The rotors to use on that brake has to be 99% true so that it doesn't rub the pads. I guess this is what help with the great modulation of this brake? Or maybe power? I have no idea about all that but the fact that this brake released almost 10yrs ago and still is ridiculously competitive against brakes released this year is insane.
I have noticed this on some pads (mostly the off brand cheap ones that are likely all made in the same factory!). They usually spin fine after 1 ride. Also I have to say I have only experienced this with the resin pads, not sintered
@@mtbphd I've been on MT7 for couple seasons now only issue that piss me off is this pad rub cuz my disc is not 99% straight...Pads I am always using the magura original ones. Disc is magura's own mdrp floating disc, out the factory bent just that tiny bit, but MT7 caliper says NO I GONNA RUB... I have no idea why they design the pad to rotor clearance on this brake to be so tight. Considering swapping disc now as they are almost wore down, or swap the whole brake.
It is a pity you can't get thick rotors in a good variety of sizes and fitments. I used to use 2.3mm Tectro discs with Shimano XT brakes and the feel was great. I'm now using Sram code rsc and wanted to use 2.3mm discs but can't find them in 220 centerlock. The extra thickness would work wonders for spongy leavers and move the bight point further out from the grip.
@@alfrednOObel2 Unfortunately my ebike came with 220 rotors and the rear speed sensor prevents 6bolt. Converting back to 203 seems like a step backward and not woth the cost.
I just nerded out on rotors yesterday. My theory is about bite and timing for rotor size and weight, along with momentum, leverage and heat is least, IMO. More about how you're breaking on trail. I was holding 2 SRAM Centerlines 220-200 and a 180mm low center mass rotors. Noticeable momentum in the SRAM, and little comparatively for 180m. The surface area, and therefore cut-outs and pattern play a factor, IMO. Look at your bike, the 203s are giving away 50% area, and pads are "switching" on/off in friction. Might as well be a 180m HS2...I say momentum bc it's relative to my riding on the street, and downhill, I use 200 and I want 220, also. I'm 220lbs fast and super aggressive and late braking...I had already decided to try the TRP 2.3" 203m rotors, to prove my theory w/ my pad choices. Pads also a key factor in works with size (greater pad friction w/better pattern 180m comparable to 203mm). Nice video. Thx
Can I use thicker brake discs (2.3mm or 2.15mm) with my Sram Code R brakes, or can I no longer get the brake disc between the brake pads even if I push the pistons back? I'm currently driving the Centerline 220mm (2mm) at the front and Centerline 200mm (1.8mm) at the rear with a Fox 38 Factory, but I'm having problems with dragging brake discs due to deformation and bending. Especially when I drive on asphalt and accelerate hard, my front brake starts to drag. This is extremely annoying. The brake caliper sits in the middle and doesn't drag when standing. However, the gap between the brake disc and the pad is so small that not even a sheet of paper would fit between them. I'm not yet satisfied with the braking power and the pressure point of the brakes, but I still use the original Sram sinter brake pads. I also have to bleed the brakes very carefully again and hope that the pressure point and free travel will then improve.
I purchased these rotors, 203 mm. Unfortunately, I was unable to install them in the SHIMANO DEORE M6120. The rotors were too thick. Colleagues, do you have any ideas on how they can be installed in this system?
You may be able to sand down your pads.....but, that reduces life and may also lessen heat dissipation as your pads reduced thickness will also reduce dissipation ( as i understand). Also, caliper will heat up more, and therefore fluid will heat up more as pads get too thin.
Hi, nice video, directly to the point. Perfect. I have some thoughts to share. 1. All forks and frames have their max permitted rotor size. Exceed it, and you may break stuff. You mentioned energy and forces, the same goes for the opposite part. 2. Almost never in engineering is bigger always better. Go to big rotors for mellow hills, light rider, small wheels, slick tires, slippery trails and you will get an unpredictable, unusable system which will lock wheels on any bump. So too small is bad, but to big is also dangerous. That braking force need to be transferred to the ground, otherwise it will be sledding. And there are hardtails too. No point for big rotor on the rear wheel in that case. The rear wheel is more in the air than on the ground. 3. Try to modulate braking power on rear wheel in manual with 220mm rotor. There is a good reason why bikes for pump track have weak brakes. Better modulation, no need to stop fast, just to slow down precisely. 4. However, thicker will be better in all cases except for wight. If your caliper will fit. I have some doubts about Shimano caliper and 2.3mm rotors. If it wouldn't rub, at lest you will not get full power because of Shimano SERVOWAVE ACTION. 5. Those data you showed are excellent and also the work you are doing. I have a possible explanation on your questions. Firs of all, smoother is better, as your coasting video suggested. The same goes for braking. Les effective weaker brakes will be smoother. So your brain is able to operate them more efficiently. You are not an ABS so you can keep up with break system efficiency only up to the point. After that, brain just give up on modulation and start to regress to old habits. Like braking mainly with rear. Also, lack of modulation makes for shorter braking time. It will be ON > skid > OFF > repeat. You may not skid totally, but enough to make your brain to release a lever. I noticed you have much better time, but as you said, the firs run was even better. So it is not totally break related. Many times I have my best time in the last run when I'm totally fatigue, almost on point of cramps. I have no energy to boost jumps, to sprint, to brake hard, but regardless it is often my fastest run of the day. 6. About braking power distribution. It all depends. The only difference between motorcycles and MTB is wight distribution. You can't shift almost all weight to the rear wheel while braking on motorcycle, but you can on MTB. However, this is possible only on ascent, not on flat and definitely not on steep descent. The closer you are to something like 45 degree down hill, you wouldn't need rear brake nor wheel. So if your rear brake heats up more, you simply underutilize your front. And full front brake utilize is harder with more effective brakes (your data agrees). Try to ride from some easy hill down using just front and then just rear break. You will be instantly sure, which one is more important and which is doing more work, so require bigger heat dissipation. As always, it is down to, ride what works the best. Or if you are a racer, what is fastest. Hope you don't died testing those cheep brakes, and we get answers and new videos soon. Good luck and keep up the good work.
@@mtbphd I'm really happy you see it that way. It is rare to meet someone who appreciate some opposition. It will be nice to see how will slope of hill change the utilization of front and rear brake. If I'm right, the steeper the slope, the more front break utilization. But it also may be totally opposite way, because rider is not a machine and fear may have a big role in it. From my own experimenting, I can say, in sufficiently steep slope you can't stop without front brake, but you can without rear.
I feel like what you should be comparing is polar moment to heat dissipation or heat storage (or a combination of both - some type of overall performance). As you know, more weight doesn’t necessarily mean more energy to spin up, or on the contrary, exponentially more energy despite having a similar scale weight (scales to square power), but also I’d be curious at what point is a rotor too large. I would think that would be the whole point of the test - everyone knows a bigger rotor is going to have more surface area, have higher velocity at the edges, provide more leverage, etc etc. it’s at what point is a rotor too big that it become a detriment rather than a benefit.
Totally, thanks for the commentary. Plenty more testing we can do, but since there's pretty much nothing on braking performance it makes sense to get heaps of data using tools and components anyone can access. (I still have PTSD from years of using wires and data loggers on bikes😁). Plenty more we can do!
I've actually experienced an edge case where I've noted decreased performance from bigger rotors. On my fat bike (snow only) I initially had 180mm rotors and had problems with them having a terrible wooden feel from the cold, being too sensitive causing lock-up, and not performing terribly well when wet (noisy chatter reducing braking efficiency). I downsized to 160mm rotors and all of the above problems have effectively gone away. I attribute it to the brakes maintaining more heat, allowing more effective drying and just being closer to their operating temperatures as well as the decreased leverage moving the exerted lever pressure into a more "normal" range. In short, you're thinking is about right. The "best" brake solution is going to depend on your riding needs. I'll admit my case is an extreme example but it does illustrate the point.
How do i find what pads fit my bike? i have a ploygon siskiu t7 with tektro brakes and i am in due need for new pads, but i am not sure what to get? help me pls
I haven't come across a brake set that is better than my Hope V4's yet. Incredible power with great modulation is hard to beat, I did upgrade to the 223mm Galfer rotor upfront and a 220mm out back.
I'm very interested to try these on my XC bike, running XTR M9020 so hopefully they will fit. Previously used any quite like the Galfer 1.8mm. Im also curious about the ZTTO 4 Piston brake set, have you tried them out at all or is that something to stay clear of?
Someone commented here that these rotors didn't fit in his Deore brakes. I haven't tried on any Shimano brakes. I have been testing those ZTTO brakes and they are not good at all. I have all the data from testing them but haven't had time to put the video together!
On my touring bike I switched to Hope V4 Calipers with their 203mm vented discs front and rear with Dot 5 fluid and braking is so much better than with normal rotors and they run cooler.
it would be awesome to see a comparison of different brake pads from different brands (noting that this would be a hefty expense as new rotors would be needed for each pad combination)
I'm a little bit concerned about a possible scenario where my MT5 brakes get hotter with thicker 2.3 rotors due to a decrease in ventilation between pads and rotors. I've heard one bike mechanic blame Formula brakes for being too hot, exactly because of that. Do you think this might be a problem and a reason to stick with my stock 2.0 Magura rotors?
@@mtbphd I'm sorry, I haven't ever seen them in person. Let's consider it just a random opinion from a random bike mechanic. I have zero ideas about whether it's true or not. It made me think about the possibility that a thicker rotor may affect an increase in brake temperatures due to worse ventilation. I thought you might have some thoughts and experience in that as an expert.
@@ThugZ3r0 I've never heard of that issue, but it does have me wondering how much air flow between the pads and rotors matters. Thanks for getting the wheels spinning! At least with this setup I didn't have a problem
@@mtbphd I noticed Galfer's comment under a guy's video yesterday. They mentioned that their rotors make "popping" noises for a reason. In their case, it's due to a special design where hot air moves through holes in the rotors, cooling them like an exhaust. I'm not sure if we should believe that or if there's any measurable statistical difference. However, common sense suggests that the space between the rotor and pads may have some effect 🤔. It would be nice to see some scientific MTB content about it!
Great Video. Sorry if this has already been asked/suggested. Would be super interesting to see you use your tech to test whether Shimano’s Ice Tech rotors make much difference vs standard.
Ice tech rotors are slightly thicker than conventional ones. The ice tech heat disippation fins at the top of the brake pads is where much of the lower temperature rise in a given scenario is gained . I have done my own controlled testing .
man... I'm riding my 26" vintage winter bike and loving the cantilevers stopping power... I've ridden 29er hydro for over a decade and just randomly wanted a cheap bike... nah it's a sick bike. stops good.
5:18 I really don't like the MT5s, I had them on my bike and the modulation was awful. I was scared to go fast because they either wouldn't stop or flip me over. I tried everything and ended up swapping them to shimano brakes.
My experience with new rotors of any thickness is similar to yours. The surface finish on new rotors are very abrasive. Machinists have gauges to measure this “roughness” in finish, and can grind the finish to various specifications. This surface will get smoother with use as the pads have various compositions that can be very abrasive. But all pads will wear away the surface finish eventually. The most grip is when they’re new and properly bed in. This is when you will have the most braking power regardless of rotor thickness.
Nah I haven't. I'd have to look into it but my first thought is that there'd be no difference in how the brakes create force, but certainly a difference in maintenance (the fluids absorb moisture differently)
@@mtbphd perhaps a difference in extreme temperatures. Not as drastic as with cars and motorcycles but something to consider in “brake science “ for cyclists in different countries
hydraulic fluid is hydraulic fluid. the differences in types are related to boiling and freezing points. as long as you're not nearing those, they will perform the same.
Operating temperature also matters, to match the optimal ranges for the pads! Rider weight and trail style also has a large impact on use case for each set of brakes. And ergo considerations. I think 203 TRP 2.3mm rotors on 27.5” wheels is my winning choice. For a 29er, I’d consider going bigger.
I have used the ZTTO heat dissipation rotors before, not sure of the thickness, but they are on par with shimano's Icetech rotors and suprior to SRAM centerline rotors. Will be checking the 2.3mm thick ones from them when its time to by new rotors.
@@mtbphd Would be curious to see how much a difference the construction of the rotor affects braking power. Icetech (Al and steel), floating, straight steel as well as finned pads. See if marketing claims can be backed up.
Really great video Matt! Been eyeing up better rotors lately and you just sold me on getting thicker ones ASAP. I tried a 220mm on front of my enduro bike and felt it was too much brake. Do you think it would be best to run a 220mm in the rear too to make it feel more balanced? I'm riding in your old stomping grounds (Blue Mountain, SALS, Glen Park). Dan
Thanks Dan! Ah man, I miss those tracks. Thicker and not bigger might really suit you there, especially considering the endless rocks. I have some TRP 2.3mm thick rotors that I can't wait to try - they just scream quality!
I went the opposite way, I went from 203 front and rear sram centerline to 180 front 160 rear shimano slx, and I didn't notice any difference, I ride plenty of double blacks and they have more than enough power, the shimano rotors for sure have more bite than the sram ones though, I tried 180 centerline rotors and they weren't powerful enough, also the sram power organic pads have more bite than their quiet organic pads.
I wish I had custom code RSCs that fit on the vented hope 3.3, I like sustained 100%+ steeps and heat management is a problem, fade or letting off = hospital. A wider braking surface would be better too, with wider pads, sometimes there's nothing left of my pads after a month. 99.99% of riders will never ride like that, so not enough demand for bigger brakes.
Yeah, sadly MTBers have an obsession with light weight gear - at the cost of performance. I had a whilte segment on that in this video but ended up cutting it out. I'm doing another one on why weight doesn't matter (there's an article on my site about it and we did a podcast on it too)
Have you considered that the thicker rotors change the bite point and that’s why they felt the way they did. I feel like a lot of this is a placebo effect. New to new would be a better comparison but I still think the bite point is what you’re feeling the most.
The bite point will be proportional to half the rotor cross - sectional thickness in hundredths of a millimetre . Check with digital verniers .I love looking at physics , chemistry and electronics .
I sometimes wonder how much a person who has completed a doctorate is going to help others working in a given field relating to it . Especially in smaller nations . I know a lady who completed a doctorate in the music field some years ago but hardly anyone has read or really benifitted from it .
This problem is exactly why I'm happy to have moved on from just research to build a product mountain bikers around the world can enjoy and benefit from. It's much more rewarding than publishing a paper in an obscure journal that nobody will read!
@@mtbphd I love your mindset . I run a small bicycle repair / building business and treat every client's ride as if it was my own . Earning loyalty and loving this industry is everything to me .
@@mtbphd The brake ace brake power accelerometer / decellerometer has one limitation , the accuracy of the analog accelerometer itself and the strain gauge likewise , depending on which initial analog data collection method is used . It is nothing more than a reciprocal power meter with sensors mounted to the hub/s . We also had hub based power meters for output power of cyclists before brake ace came about. It simply was a modification of a power meter . We had brake analysis software on millenium trains where I live in Australia . Developed by Downer Engineering in 2000 . Brakeace is simply a slight adaptation of this . The software was largely inspired by existing systems in transportation .
@@robertmcfadyen9156 the electronics inside BrakeAce are power metre electronics. Our tech wiz rewrote the firmware so they could be used to measure brake torque/power. The accelerometer is only used to wake up the sensor (by bouncing the bike). Torque is strain gauge based.
This rotor comparison topic is a very challenging one to explain .The biggest reason is the good number of stencillings and patterns used by one manufacturer over the years as well as the huge number of brands and overall design variations . I have about 80 styles in stock . Testing is possibly a nightmare . Some rotors in a given brand and size mostly have a pattern variation between sizes , I found .
@@mtbphd Yes . When choosing rotors , I focus on the relationship between pad contact area and ventilation gaps . TRP rotors are moerately priced and value for money. I stock them .
I've switched to thicker rotors for some time and i didn't notice any difference in breaking performance whatsoever. So it only brings negatives being unsprung weight. As long as overheating is not an issue, thicker rotors will be an overall net negative.
I have tried trp 2.3 mm 203 rotors with copper metallic pads on my Jeckyll it works pretty much the same as the 1.9 mm floating rotors on my trance x 29 with ceramics, Jeckyll has codes RSC trance has SRAM db8's.
@@garyking508 read my comment again. I didn't say that I wanted or expected more power. I said that theres no benefit to be had from thicker rotors, other than them being a bigger heatsink. But youll gain ~100g of unsprung weight! So ill repeat myself: "As long as overheating is not an issue, thicker rotors will be an overall net negative." I am already on 220 mm discs, but they are normal sized 1.8 mm thick...
You can straighten thicker rotors more easily as well I have Shimano ice tech rotors from 2015, they are way too thin, the rear one is rubning but there's nothing we can really do about it, the mechanics at the shop have tried, you try to straighten it and it just ends up bending the other way and rubbing on the other side instead. Also rotor wear. Thicker ones will last longer before getting too thin for the brakes to actually work. Also even if your rotors
@@mtbphd according to the mechanics, they made them a bit too thin. It supposedly helps with cooling since there's more surface area for the volume but being so thin coupled with being 2 piece rotors makes them really hard to straighten out.
Why not black rotors. The dark color will release more heat. Even where not contact with the pad, a painted surface will help radiate heat. Yes, the dark color will radiate more than the paint insulates.
I could be wrong, but my days working in electronics a million years ago tells me that black is better at absorbing heat from light. I don't think color (or black) makes a difference in releasing/dissipating heat. In fact, on a hot sunny day, black may be counter productive because it's absorbing heat from the sunlight. ..just a wild-ass guess.
Bigger rotor on the front doesn't make sense in MTB since riders brake more with the rear brake. On motorcycles and road we get higher brake power with the front brake so I can see the argument for motorcycles at least
@@mtbphd CRF450R 2024 Specifications Brakes FronT Single 260mm disk Brakes Rear Single 240mm disk THIS IS A FULL ON MOTO X AND ITS IRELEVENT THE MODE OF TRANSPORT THE PHYSICS IS THE SAME
@@wraith600original1You might like this podcast episode. It's all about why most MTB riders don't use the front brake enough. Also gotta keep in mind that a lot of braking in MTB is to avoid going faster, rather than to slow down. Big difference in how the brakes are used open.spotify.com/episode/5yvyi8mTBcy4JrckHDZ3zx?si=yhXI-6juTdWjYiUU_ulBOQ
i stopped the video at 3:16 when you said that there are people that didn't upgrade to bigger rotors because they think there is not enough ground clearance but they are ok with a dirt scraping 12 speed derailleur.... i know two S companies that make a lot of $ from these people...
That's a great topic, but the design of your experiment seems rather basic for a Ph.D. level scientist, as you mentioned yourself. It would be truly interesting to see measurable data on how it affects braking power, the amount of braking before fading, cooling down later, etc. Also, having proper control rotors, which are also new, would be valuable. Investigating the hardness of the ZTTO rotor, measured in HRC for example, and comparing it to branded ones could provide insights into its longevity in a long run.
@@mtbphd true talk, bro! Mainstream is more about grimacing tiktoks, whyle channels which are really into deep stuff like Volfsprung or Love.bike (some neardy stuff about chemistry in russian) are getting just tens thousands
I have as I call, pornography of brakes: slx 7120 levers, mt520 calipers, zee finned brake pads and 2x ice tech 203mm rotors, best brakes I've had so far. On ebike with total riding mass 124kg, works very well.
For the sake of learning to be a better rider, and simple curiosity, I’d like to find a way to make observations like this on my e-bike. I am especially interested in the possibility of abs systems with large diameter thick rotors on MTB, both traditional and electric. Awesome video btw, I’m learning tons here.
Don't buy Chinese made Shimano disc rotors, why because that are only 1.7-1.6mm thick and the two sets I purchased from the bike shop were only 1.6mm. When I questioned the bike shop they had no answer, only to say that is what Shimano Australia supplied them. What's the problem, simple stamped on the disc is a warning to replace the rotors once the reach 1.5mm, so you only get 0.1mm of wear before they have to be replaced. The Japanese Shimano rotors are 1.9-1.8mm thick and they also are stamped and state they should be replaced when they reach 1.5mm thick. I have dumped Shimano and gone with 203mm Tektro rotors that measured 2.0mm thick and are also stamped to be replaced when they are 1.5mm thick. They were half the price of the Shimano Chinese made rotors. Now that I know there are such a thing as 2.3mm thick rotors I did consider buying some however a note of warning. I have read that they should be to be used with calipers that are designed for 2.3mm discs. With that additional cost it is not worth the added expense as I only do XC and any down hill sections are only short descents.
calipers use a piston to contact the rotor. as long as it fits between new pads and the surface area covers the pad area... you are good. the idea that the caliper is designed for a smaller thickness but has physical room for a larger one just doesn't make sense to me.
Some caution should be advised I think. Some forks and frames can only go so big on rotor size and some calipers may not be compatible with the thick rotor trend also.
It amazes me that the bike industry is trying to recreate the wheel with brake size, thickness and power. As a former road racer and sport bike motorcyclist for nearly 30 years and mountain biker since the late 80’s, it’s well understood that better braking comes from larger and thicker rotors. Rotors that are drilled and float as well make substantial differences. The mix of steeper descents and faster speeds warrant larger thicker rotors 200mm and larger, where’s the average enduro, XC or trail bike will be best suited with no more than 203mm to 160mm rotors. It’s hard to take all this data collecting serious for something that is I’d say common knowledge in other communities. Anything over 200mm on a trail bike is overkill. Also, I’ll note that your info speaks nothing of the gyroscopic forces that come into play with rotors larger that 203mm.
These fit all good. Not sure how those new 3mm thick rotors would fit, but I suspect new brakes will all be designed for thicker rotors from now on (since it makes sense and always did!)
And you grind through a key structural element of the wheel with every brake appliction...an element that is expensive and difficult to replace, and fails catastrophically (at least if you're willing to concede that an instant flat tire is catastrophic).
@@xanthoptica most rims are made ultra light, but heavier duty rims work very well, and it's not terrible to replace them if you have good nipple and spoke components. Discs are easier to swap, but rim brakes still have a place for low cost and hardiness for most riders.
I think this test would greatly benefit from testing with only new rotors, and with only rotors with the same design. I've tried several brands of rotors a decade ago and there were huge difference between some brake design, even in the same alloy.
For sure, thanks for the comment. What were the differences you noticed?
for ebikes, brakes seem to generally be undersized - not taking into account the higher mass of the bike and larger rotational mass of the usually fat tires.
would be interesting to see what kind of temps they see when braking to a stop from 30mph. and how that is impacted by thicker rotors at the same diameter vs a larger diameter rotor of about the same mass as the thicker upgrade one. assuming a thicker one fits in the test bike.
it's too bad rotors aren't forced to be sold with a wattage rating of how much they can peak absorb and how much they can constantly absorb at room temp. then you could estimate if it's good enough for your use fairly directly.
Yeah that would be cool. Most people wouldn't know how many braking watts they achieve, but it's easy to calculate ((change in kinetic energy - rolling resistance - aerodynamic drag)/braking time). Saying that though heat accumulation in the brakes is more than one-off change in speed -- depends a lot on how the rider is dragging the brakes through the ride, which varies on the trail, the rider, and how purposeful they are with their braking
@@mtbphd I'm thinking two variables that may matter is how fast can the rotor return to safe temp from say 120c while spinning at like 15mph. and how fast does it heat up to 120c using some kind of iso standard brake process.
with an ebike a few ounces isn't going to matter .. so i wouldn't mind adding some to have better brakes. it sounds to me like going bigger is better... and go as thick as your calipers can handle
@@mtbphd Is it really that crucial? Isn't it more about maximizing the average heat transfer capability? (Function of rotors' surface and some coefficient related to the speed and airflow around the material)
Thicker rotors increase heat capacity, i.e. let the rotor absorb more heat before fading occurs, but I guess that impact on the surface that dissipates the heat is negligible. On the other hand, heat dissipation speed is proportional to the difference of temperatures so the thicker one may be dissipating the same energy at a slower rate due to lower gradient of temperatures?
In the context of heat buildup isn't the elevation change of the trail a dominating factor? Braking from 40km/h down to full stop transfers into heat energy equal to slightly over 12m of elevation change (yes, I'm ignoring here the aero drag). That seems like nothing compared to the difference of potential energies between the start and the end of a downhill trail. Assuming that rolling resistance is negligibly small compared to the braking power or aero drag on faster sections, I bet that required heat dissipation speed could be approximated with a function of inclination, average speed, mass and aero drag coefficient (maybe also some coefficient describing the impact of the airflow on the cooling speed of the brake).
Therefore, it seems like the optimal strategy for minimizing the heat buildup in rotos is to brake as short and as intensive as possible (the shorter braking times, the higher braking power and higher temperature gradient; the more and faster the rider goes, the smaller energy to dissipate in brakes due to aero drag) with the rotor that has enough, but not much more heat capacity, to stay within a planned temperature limit for a given trail?
@@BZab_ totally. Lots to consider!
I've always loved the feel i get from 203mm rotors, both front and back and never gone smaller diameters again. Haven't had any fading situation with the brakes with different brake systems (shimano, sram and now hopes) with the 203s. Loving your rational take on the subject. Have a nice day!
Sounds like you found the perfect setup 🙌 thanks for the comment 🤜🤛
I also put 203mm rotors on all my bikes, but I don’t ride any lightweight short travel xc bikes.
If you were actually interested in a scientific or engineering test of the effect of rotor thickness on braking...this is the LAST way you would do it. Experts generally start with tests under controlled conditions that evaluate something specific; in this case, for example, there seems to be a hypothesis that a thicker rotor will store more heat and therefore temperatures will climb more slowly under braking. Great! Put together a setup that puts the same braking force into rotors of different thicknesses, and measure the temperature over time with an IR thermometer or embedded thermocouple. You could add realistic amounts of airflow, if you like, but the key factor would be isolating the factor you are interested in and reducing or eliminating the effects of confounding variables/factors, and doing an objective measurement that tests your hypothesis.
What does "MTB PhD" do? On-trail testing with every possible confounding factor included, with a sample size of two tests per rotor thickness (!). He concedes that there is a wear difference between the thin and thick rotors (oops!), but neglects all the complex factors in his psychology and technique that could produce different results. He also doesn't have any kind of objective way to evaluate differences, beyond the "feel" or how he behaviorally braked. Did heat storage affect the effectiveness of his brakes? He literally can't tell you.
Real-world testing only works when you have a large enough sample to isolate the variable you're interested in from all those other confounding factors. In this case you'd need both an objective measurement and likely tens of attempts from 40-50 different riders. Needless to say, this "test" isn't even close to the statistical power you'd need to make any kind of reliable conclusion.
To be fair to "MTB Phd" he's hardly the only one putting meaningless tests out there as "science." Pretty much everything GCN labels as "science" suffers from the same flaws and is just as meaningless. You would just hope that somebody who sold themselves with research credentials would not jettison everything they learned doing that research when they started recording for TH-cam. And "with REAL Proof"? That's just clickbait snake oil.
Thanks Duncan. That would make a rad test.
Harsh, but true. For statistical power, you need to either eliminate or account for confounding factors. And the way this is reported is a point estimate in the difference in heat dissipation among rotors with a confidence interval at a given confidence level.
I work in automotive testing. I'm curious if you've ever experimented with DGPS systems such as OxTS or RaceLogic for any of your data collection. I suspect that signals from the IMUs involved would be too noisy to be useful with mountain biking, but I don't know of anybody who has actually tried it. Have you looked in to anything like that?
Oh nice, are IMUs handy for you? I used IMUs back in 2014/15 continuing some of Paul Macdermids work on vibration exposure in MTB but haven't looked at that kind of data since. The BYB and AiM loggers have accelerometers and gyros. I think a few guys look at the data at the world cups.
@@mtbphd I wasn't familiar with those data loggers. I think I have something new to look into now. Thank you!
On my 130mm trail bike with 203/180mm with 1.8mm thickness, on my 160mm enduro 203/180mm with 2mm. Besides thinkness also pad compound trail uses organic/resin, enduro was sinstered now ceramic
Pad compound would be an awesome test 🤤🤤🤤 resin all day!!!
What calipers are you using on both of these bikes? I have Shimano's on my trail hardtail (Deore 2 piston) and enduro bike (SLX 4 piston), running 1.8mm Galfers 203mm front and 180mm rear rotors. Stopping power isn't an issue with either. I wanted to move up to 2mm thick, but I don't think there's enough clearance, unless you're using used/slightly used pads. New pads I don't think it's happening, and I don't feel like buying 2mm rotors just to test that.
What do you think @mtbphd?
@@Beiberhole69RVA Dominion A4 with the 2.0, Sram G2 with the 1.8
I agree, i went from shimano to magura rotors and have never gone back...thicker rotors allow faster brake pad engagement...givng me more immediate feedback and confidence
Nice one mate. Which Magura rotors?
Pad clearance or engagement speed as you put it are not controlled by the rotor thickness.
The square edge seal inside the caliper and the fluid viscosity is what controls this.
What you did was simply put a thicker rotor in without resetting the pistons and found you have less clearance.
This will reset itself after a few rides as the pads wear and will feel identical to the previous rotor.
@@darrylduck6356Exactly what I was thinking. But not sure if viscosity would come into it (unless insanely thick fluid was use for some reason) as that would only affect flow, not pressure on the pistons. Also the seals are so small that I'd think the pad springs would have the main influence on retraction.
Any tips on how to adjust pistons / pads to fit these thicker rotors? I just installed some new 203 x 2.3 mm rotors and they are dragging?
Did you try resetting your pistons?
I followed your suggestions about two years ago and I have been super happy with your data and my first hand account. Thanks.
Awesome to hear! Cheers mate
Speaking from car experience, more mass means more heat asorbtion. But, one thing to keep in mind is heat dissipation. Larger diameter means more surface area. Which in turn will give faster heat dissipation. When it comes to brakes, you want the mass increase from diameter. Leverage, surface area and mass.
Good points mate, cheers
Thicker rotors will tend to warp less when at maximum temp and over the long-term AND absorb/dissipate heat more efficiently.
Galfer 246 on my (recently stolen) ebike. Galfer green pads or MTX pads. Really helps with hand pump.
Heck yes!
I've had 9 months experience riding a fast e-scooter and ive found that a thinner rotor not only dissipates heat faster, with the right blend of stainless steel and alloy... much like Shimano's ICE rotor.
But the 140mm 6-bolt im currently using is significantly lighter and suprisingly doesnt need realigning after every
40 k ride on 30°C + days.
Interesting. I wonder how braking compares on a MTB on trails versus braking on an e-scooter (guessing on road)?
3x spoke lacing is the strongest because the spokes are the most tangent to the hub. It also has leading and trailing spokes so that there are always spokes in tension. I don't see much of that thinking in some of these rotors -- is the force distribution that different, or are they just making pretty patterns and assuming that the steel is more than strong enough?
Good point and good question. I believe rotor design patterns are just about fashion. As long as they don't fold under the heaviest of braking, they're fine (and I've seen this happen twice - once last week with an off brand, and once with a pre-production rotor from a very well known brand).
One difference with wheels that is worth pointing out is that there isn't much side-to-side flex in rotors. However some frames aren't stiff enough and allow the hubs to flex under heavy cornering - we can measure this with the BrakeAce Scientific sensor (plus some pros rub holes in their frames with the rotor edges)
Hey Brutha. I received the Ali express 2.3 203 rotors. One of them has a very fine scratch on one side of the braking surface. Do you think I should ask for a replacement? Or will it not be noticeable once bedded? Thanks
Nice! Your only chance to ask for a replacement would be before you use it, so I'd probably try to get that now instead of seeing what happens. (Even though I don't know what will happen!)
I think I will just try the one that’s scratched. Then if it is noticeable I’ll buy another. Wish they had 22m. The machining is not as course as Galfer (my preference) but courser than sram (shiny = grabby from my experience). Anyways I won’t be on my DH bike for 18 months so I’ll probably forget about the wcratch
How do you calculate braking force?
The BrakeAce sensors used strain gauges to measure the force of the caliper pushing on the frame or fork
Will the thicker discs work with most calipers? I am about to build an 8000 watt emtb and think they would a good addition along with regen braking.
Good question. I don't know but hopefully someone here will. Unfortunately most manufacturers will simply say that their calipers were designed to be used with their rotors, so not sure if you'll get any real answers from them.
Yeah, that was pretty much what I thought, depends. I really like this idea for a couple reasons, I am a larger rider that rides hard and an ebike rider that is using 160mm rotors and to feel safer need better brakes. Thanks again for the research you presented!
@@mtbphd
As long as they physically clear the caliper I can't see why they wouldn't as the pistons will still move within their defined range, just with a starting point slightly further apart. I can't see how this would be any different than varying pad thickness.
That said, you should plan on a brake bleed/piston cleaning when you go with thicker rotors.
I'm curious on what do you think the effect is on caliper pad to rotor clearance? I use MT7 myself and the pad clearance on that caliper is nuts u don't even see light coming out of it. The rotors to use on that brake has to be 99% true so that it doesn't rub the pads. I guess this is what help with the great modulation of this brake? Or maybe power? I have no idea about all that but the fact that this brake released almost 10yrs ago and still is ridiculously competitive against brakes released this year is insane.
I have noticed this on some pads (mostly the off brand cheap ones that are likely all made in the same factory!). They usually spin fine after 1 ride. Also I have to say I have only experienced this with the resin pads, not sintered
@@mtbphd I've been on MT7 for couple seasons now only issue that piss me off is this pad rub cuz my disc is not 99% straight...Pads I am always using the magura original ones. Disc is magura's own mdrp floating disc, out the factory bent just that tiny bit, but MT7 caliper says NO I GONNA RUB... I have no idea why they design the pad to rotor clearance on this brake to be so tight. Considering swapping disc now as they are almost wore down, or swap the whole brake.
It is a pity you can't get thick rotors in a good variety of sizes and fitments. I used to use 2.3mm Tectro discs with Shimano XT brakes and the feel was great. I'm now using Sram code rsc and wanted to use 2.3mm discs but can't find them in 220 centerlock. The extra thickness would work wonders for spongy leavers and move the bight point further out from the grip.
Yeah sometimes I wonder if centerlock will become standard, but 6 bolt tends to be more common. So maybe that's what makes them harder to find
You can get TRP R1C rotors in 2.3 mm centerrlock. I've just got mine, but still waiting for the better conditions to test them.
@@alfrednOObel2 Unfortunately my ebike came with 220 rotors and the rear speed sensor prevents 6bolt. Converting back to 203 seems like a step backward and not woth the cost.
Or just ditch the spongy sram...
Try motor bicycle parts
Can the zitto 2.3 rotor fit with sram db8 6 bolt?
Is there any brake pads you know equivalent to mtx pads?
Not sure on compatibility with the DB8. For pads I often use generic brands and haven't had any issues. Worth a try!
I just nerded out on rotors yesterday. My theory is about bite and timing for rotor size and weight, along with momentum, leverage and heat is least, IMO. More about how you're breaking on trail. I was holding 2 SRAM Centerlines 220-200 and a 180mm low center mass rotors. Noticeable momentum in the SRAM, and little comparatively for 180m. The surface area, and therefore cut-outs and pattern play a factor, IMO. Look at your bike, the 203s are giving away 50% area, and pads are "switching" on/off in friction. Might as well be a 180m HS2...I say momentum bc it's relative to my riding on the street, and downhill, I use 200 and I want 220, also. I'm 220lbs fast and super aggressive and late braking...I had already decided to try the TRP 2.3" 203m rotors, to prove my theory w/ my pad choices. Pads also a key factor in works with size (greater pad friction w/better pattern 180m comparable to 203mm). Nice video. Thx
Braking is everything! 🙌
I’m gonna try it, my DH and e-bike both seem to have so much room I’m constantly resetting the pistons as the pad wear.
I know the feeling. What brakes? Maybe they need another bleed
@@mtbphd e-bike shamano, DH SRAM
Can I use thicker brake discs (2.3mm or 2.15mm) with my Sram Code R brakes, or can I no longer get the brake disc between the brake pads even if I push the pistons back? I'm currently driving the Centerline 220mm (2mm) at the front and Centerline 200mm (1.8mm) at the rear with a Fox 38 Factory, but I'm having problems with dragging brake discs due to deformation and bending. Especially when I drive on asphalt and accelerate hard, my front brake starts to drag. This is extremely annoying. The brake caliper sits in the middle and doesn't drag when standing. However, the gap between the brake disc and the pad is so small that not even a sheet of paper would fit between them. I'm not yet satisfied with the braking power and the pressure point of the brakes, but I still use the original Sram sinter brake pads. I also have to bleed the brakes very carefully again and hope that the pressure point and free travel will then improve.
Sounds like a tight squeeze. Wonder if the pads are thicker than normal?
I purchased these rotors, 203 mm.
Unfortunately, I was unable to install them in the SHIMANO DEORE M6120. The rotors were too thick. Colleagues, do you have any ideas on how they can be installed in this system?
You may be able to sand down your pads.....but, that reduces life and may also lessen heat dissipation as your pads reduced thickness will also reduce dissipation ( as i understand). Also, caliper will heat up more, and therefore fluid will heat up more as pads get too thin.
Bummer. I don't have any Shimano brakes, so never tried. Did you reset the pistons?
Hi, nice video, directly to the point. Perfect. I have some thoughts to share.
1. All forks and frames have their max permitted rotor size. Exceed it, and you may break stuff. You mentioned energy and forces, the same goes for the opposite part.
2. Almost never in engineering is bigger always better. Go to big rotors for mellow hills, light rider, small wheels, slick tires, slippery trails and you will get an unpredictable, unusable system which will lock wheels on any bump. So too small is bad, but to big is also dangerous. That braking force need to be transferred to the ground, otherwise it will be sledding. And there are hardtails too. No point for big rotor on the rear wheel in that case. The rear wheel is more in the air than on the ground.
3. Try to modulate braking power on rear wheel in manual with 220mm rotor. There is a good reason why bikes for pump track have weak brakes. Better modulation, no need to stop fast, just to slow down precisely.
4. However, thicker will be better in all cases except for wight. If your caliper will fit. I have some doubts about Shimano caliper and 2.3mm rotors. If it wouldn't rub, at lest you will not get full power because of Shimano SERVOWAVE ACTION.
5. Those data you showed are excellent and also the work you are doing. I have a possible explanation on your questions.
Firs of all, smoother is better, as your coasting video suggested. The same goes for braking. Les effective weaker brakes will be smoother. So your brain is able to operate them more efficiently. You are not an ABS so you can keep up with break system efficiency only up to the point. After that, brain just give up on modulation and start to regress to old habits. Like braking mainly with rear. Also, lack of modulation makes for shorter braking time. It will be ON > skid > OFF > repeat. You may not skid totally, but enough to make your brain to release a lever. I noticed you have much better time, but as you said, the firs run was even better. So it is not totally break related. Many times I have my best time in the last run when I'm totally fatigue, almost on point of cramps. I have no energy to boost jumps, to sprint, to brake hard, but regardless it is often my fastest run of the day.
6. About braking power distribution. It all depends. The only difference between motorcycles and MTB is wight distribution. You can't shift almost all weight to the rear wheel while braking on motorcycle, but you can on MTB. However, this is possible only on ascent, not on flat and definitely not on steep descent. The closer you are to something like 45 degree down hill, you wouldn't need rear brake nor wheel. So if your rear brake heats up more, you simply underutilize your front. And full front brake utilize is harder with more effective brakes (your data agrees). Try to ride from some easy hill down using just front and then just rear break. You will be instantly sure, which one is more important and which is doing more work, so require bigger heat dissipation. As always, it is down to, ride what works the best. Or if you are a racer, what is fastest.
Hope you don't died testing those cheep brakes, and we get answers and new videos soon. Good luck and keep up the good work.
Good points mate, thanks for the comment 🤜🤛
@@mtbphd I'm really happy you see it that way. It is rare to meet someone who appreciate some opposition.
It will be nice to see how will slope of hill change the utilization of front and rear brake. If I'm right, the steeper the slope, the more front break utilization. But it also may be totally opposite way, because rider is not a machine and fear may have a big role in it. From my own experimenting, I can say, in sufficiently steep slope you can't stop without front brake, but you can without rear.
@@islandershome7126 only one way to find out 😁😁😁
That’s so cool!
How are you tracking the brake data?
Thanks mate! We collected all the braking data with BrakeAce 👍
Slapped on 223/203 on my Trek rail. What a difference compared to the oem Sram 200's. It was a cheap upgrade with a lot of benefits.
So simple but so often overlooked!
I feel like what you should be comparing is polar moment to heat dissipation or heat storage (or a combination of both - some type of overall performance). As you know, more weight doesn’t necessarily mean more energy to spin up, or on the contrary, exponentially more energy despite having a similar scale weight (scales to square power), but also I’d be curious at what point is a rotor too large. I would think that would be the whole point of the test - everyone knows a bigger rotor is going to have more surface area, have higher velocity at the edges, provide more leverage, etc etc. it’s at what point is a rotor too big that it become a detriment rather than a benefit.
Totally, thanks for the commentary. Plenty more testing we can do, but since there's pretty much nothing on braking performance it makes sense to get heaps of data using tools and components anyone can access. (I still have PTSD from years of using wires and data loggers on bikes😁). Plenty more we can do!
I've actually experienced an edge case where I've noted decreased performance from bigger rotors. On my fat bike (snow only) I initially had 180mm rotors and had problems with them having a terrible wooden feel from the cold, being too sensitive causing lock-up, and not performing terribly well when wet (noisy chatter reducing braking efficiency).
I downsized to 160mm rotors and all of the above problems have effectively gone away. I attribute it to the brakes maintaining more heat, allowing more effective drying and just being closer to their operating temperatures as well as the decreased leverage moving the exerted lever pressure into a more "normal" range.
In short, you're thinking is about right. The "best" brake solution is going to depend on your riding needs. I'll admit my case is an extreme example but it does illustrate the point.
How do i find what pads fit my bike? i have a ploygon siskiu t7 with tektro brakes and i am in due need for new pads, but i am not sure what to get? help me pls
Try to find what model brakes you have on the brand website. Sometimes not printed on the brakes themselves
@@mtbphd i know The model and everything(Tektro HD-M735) but i cant find anything about them or what pads to use. help?
@@DarcyFletchh you'll be fine with any pads that fit that model mate. Don't worry too much about all the other options
@@mtbphd oh ok cool, is there a specific shape for each different brakes or should I just look at the shape of mine and find ones that match
@@DarcyFletchh just needs to be compatible with your model
I haven't come across a brake set that is better than my Hope V4's yet. Incredible power with great modulation is hard to beat, I did upgrade to the 223mm Galfer rotor upfront and a 220mm out back.
Nice, that's one brake I never tried
It's leaps and bounds better than anything I've tried in the past and I've been in the mountain bike game of very long time
I have been using ztto 203mm rotors since last year cheap and big upgrade to my braking.
That's awesome to hear
I'm very interested to try these on my XC bike, running XTR M9020 so hopefully they will fit. Previously used any quite like the Galfer 1.8mm. Im also curious about the ZTTO 4 Piston brake set, have you tried them out at all or is that something to stay clear of?
Someone commented here that these rotors didn't fit in his Deore brakes. I haven't tried on any Shimano brakes.
I have been testing those ZTTO brakes and they are not good at all. I have all the data from testing them but haven't had time to put the video together!
I appreciate the prompt reply, have a primo arvo! @@mtbphd
On my touring bike I switched to Hope V4 Calipers with their 203mm vented discs front and rear with Dot 5 fluid and braking is so much better than with normal rotors and they run cooler.
And touring bike brakes get HOT! (High load plus high speed)
DOT 5? Or 5.1? Because DOT 5 is not not compatible with the Hope brakes and may lead to brake failure. Just a friendly warning 👍
@@jordankitching1501 I meant Dot 5.1.
it would be awesome to see a comparison of different brake pads from different brands (noting that this would be a hefty expense as new rotors would be needed for each pad combination)
People would love to see that comparison. I agree it would be awesome!
@@mtbphd Expense for fresh rotors isn''t too bad with the ztto rotors. I just bought a wack of them to update the fleet.
I'm a little bit concerned about a possible scenario where my MT5 brakes get hotter with thicker 2.3 rotors due to a decrease in ventilation between pads and rotors. I've heard one bike mechanic blame Formula brakes for being too hot, exactly because of that. Do you think this might be a problem and a reason to stick with my stock 2.0 Magura rotors?
What rotors are used with the Formula brakes?
@@mtbphd I'm sorry, I haven't ever seen them in person. Let's consider it just a random opinion from a random bike mechanic. I have zero ideas about whether it's true or not. It made me think about the possibility that a thicker rotor may affect an increase in brake temperatures due to worse ventilation. I thought you might have some thoughts and experience in that as an expert.
@@ThugZ3r0 I've never heard of that issue, but it does have me wondering how much air flow between the pads and rotors matters. Thanks for getting the wheels spinning! At least with this setup I didn't have a problem
@@mtbphd I noticed Galfer's comment under a guy's video yesterday. They mentioned that their rotors make "popping" noises for a reason. In their case, it's due to a special design where hot air moves through holes in the rotors, cooling them like an exhaust. I'm not sure if we should believe that or if there's any measurable statistical difference. However, common sense suggests that the space between the rotor and pads may have some effect 🤔. It would be nice to see some scientific MTB content about it!
Great Video. Sorry if this has already been asked/suggested. Would be super interesting to see you use your tech to test whether Shimano’s Ice Tech rotors make much difference vs standard.
Thank you! 🤜🤛 I had a few people ask or DM about an ice tech test. Hoping someone else gets to it first 😁
Ice tech rotors are slightly thicker than conventional ones. The ice tech heat disippation fins at the top of the brake pads is where much of the lower temperature rise in a given scenario is gained . I have done my own controlled testing .
It made a difference for me, but I’m a heavy rider at about 220 lbs (almost 100 kg).
Good stuff mate 🤜🤛
man... I'm riding my 26" vintage winter bike and loving the cantilevers stopping power... I've ridden 29er hydro for over a decade and just randomly wanted a cheap bike... nah it's a sick bike. stops good.
Yeah they can surprisingly lock the wheel nicely!
5:18 I really don't like the MT5s, I had them on my bike and the modulation was awful. I was scared to go fast because they either wouldn't stop or flip me over. I tried everything and ended up swapping them to shimano brakes.
Interesting. I feel like they're always there when I need them. Resin pads
@@mtbphd I had metal pads, i need a lot of braking power since I'm tall and heavy.. Might've been that the specific ones I had were faulty
My experience with new rotors of any thickness is similar to yours. The surface finish on new rotors are very abrasive. Machinists have gauges to measure this “roughness” in finish, and can grind the finish to various specifications.
This surface will get smoother with use as the pads have various compositions that can be very abrasive. But all pads will wear away the surface finish eventually. The most grip is when they’re new and properly bed in. This is when you will have the most braking power regardless of rotor thickness.
I wonder what the actual maximum usage is. Manufacturers always state a minimal thickness, but I give up on rotors way before that!
Have you tested or noticed a difference between DOT brake fluid brakes and mineral oil brakes.
Nah I haven't. I'd have to look into it but my first thought is that there'd be no difference in how the brakes create force, but certainly a difference in maintenance (the fluids absorb moisture differently)
@@mtbphd perhaps a difference in extreme temperatures. Not as drastic as with cars and motorcycles but something to consider in “brake science “ for cyclists in different countries
hydraulic fluid is hydraulic fluid. the differences in types are related to boiling and freezing points. as long as you're not nearing those, they will perform the same.
Yep, I use the same ztto rotor and notice no difference from the more expensive TRP rotor
Still going strong for me!
Operating temperature also matters, to match the optimal ranges for the pads!
Rider weight and trail style also has a large impact on use case for each set of brakes. And ergo considerations.
I think 203 TRP 2.3mm rotors on 27.5” wheels is my winning choice. For a 29er, I’d consider going bigger.
I just installed some of those TRP rotors on my trail bike and they ride great👌
I have used the ZTTO heat dissipation rotors before, not sure of the thickness, but they are on par with shimano's Icetech rotors and suprior to SRAM centerline rotors. Will be checking the 2.3mm thick ones from them when its time to by new rotors.
That's awesome. I never knew they existed before this!
@@mtbphd Would be curious to see how much a difference the construction of the rotor affects braking power. Icetech (Al and steel), floating, straight steel as well as finned pads. See if marketing claims can be backed up.
Hey can you tell me how you found these rotors on Ali express? Me WANT!!!
I put a link in the description for these 2.3 rotors. They were kind of hidden in there
Found them!! Thanks. Let me know if you find 223mm or 246mm rotors for ebiking!!!
🙌🙌🙌
Really great video Matt! Been eyeing up better rotors lately and you just sold me on getting thicker ones ASAP. I tried a 220mm on front of my enduro bike and felt it was too much brake. Do you think it would be best to run a 220mm in the rear too to make it feel more balanced? I'm riding in your old stomping grounds (Blue Mountain, SALS, Glen Park). Dan
Thanks Dan! Ah man, I miss those tracks. Thicker and not bigger might really suit you there, especially considering the endless rocks. I have some TRP 2.3mm thick rotors that I can't wait to try - they just scream quality!
To much brake?? Learn to modulate better
@@mtbphdI have a fitter machinist friend that can make me prescription rotors if I want them .
I went the opposite way, I went from 203 front and rear sram centerline to 180 front 160 rear shimano slx, and I didn't notice any difference, I ride plenty of double blacks and they have more than enough power, the shimano rotors for sure have more bite than the sram ones though, I tried 180 centerline rotors and they weren't powerful enough, also the sram power organic pads have more bite than their quiet organic pads.
Interesting! Thanks for the comment. Yeah gotta love organic pads - I'd never go back
Post mount adapter for 246 ?
Pretty sure Galfer make some adapters to go with their 246 rotor
I wish I had custom code RSCs that fit on the vented hope 3.3, I like sustained 100%+ steeps and heat management is a problem, fade or letting off = hospital. A wider braking surface would be better too, with wider pads, sometimes there's nothing left of my pads after a month. 99.99% of riders will never ride like that, so not enough demand for bigger brakes.
Yeah, sadly MTBers have an obsession with light weight gear - at the cost of performance. I had a whilte segment on that in this video but ended up cutting it out. I'm doing another one on why weight doesn't matter (there's an article on my site about it and we did a podcast on it too)
TRP 2.3 rotors are my go
Rocking those now with my Radic Kahas and love em
Have you considered that the thicker rotors change the bite point and that’s why they felt the way they did. I feel like a lot of this is a placebo effect. New to new would be a better comparison but I still think the bite point is what you’re feeling the most.
Yeah definitely could be
The bite point will be proportional to half the rotor cross - sectional thickness in hundredths of a millimetre . Check with digital verniers .I love looking at physics , chemistry and electronics .
I sometimes wonder how much a person who has completed a doctorate is going to help others working in a given field relating to it . Especially in smaller nations . I know a lady who completed a doctorate in the music field some years ago but hardly anyone has read or really benifitted from it .
This problem is exactly why I'm happy to have moved on from just research to build a product mountain bikers around the world can enjoy and benefit from. It's much more rewarding than publishing a paper in an obscure journal that nobody will read!
@@mtbphd I love your mindset . I run a small bicycle repair / building business and treat every client's ride as if it was my own . Earning loyalty and loving this industry is everything to me .
@@mtbphd The brake ace brake power accelerometer / decellerometer has one limitation , the accuracy of the analog accelerometer itself and the strain gauge likewise , depending on which initial analog data collection method is used . It is nothing more than a reciprocal power meter with sensors mounted to the hub/s . We also had hub based power meters for output power of cyclists before brake ace came about. It simply was a modification of a power meter . We had brake analysis software on millenium trains where I live in Australia . Developed by Downer Engineering in 2000 . Brakeace is simply a slight adaptation of this . The software was largely inspired by existing systems in transportation .
@@robertmcfadyen9156 the electronics inside BrakeAce are power metre electronics. Our tech wiz rewrote the firmware so they could be used to measure brake torque/power. The accelerometer is only used to wake up the sensor (by bouncing the bike). Torque is strain gauge based.
This rotor comparison topic is a very challenging one to explain .The biggest reason is the good number of stencillings and patterns used by one manufacturer over the years as well as the huge number of brands and overall design variations . I have about 80 styles in stock . Testing is possibly a nightmare . Some rotors in a given brand and size mostly have a pattern variation between sizes , I found .
That would take a long time 😁
@@mtbphd Yes . When choosing rotors , I focus on the relationship between pad contact area and ventilation gaps . TRP rotors are moerately priced and value for money. I stock them .
I've switched to thicker rotors for some time and i didn't notice any difference in breaking performance whatsoever. So it only brings negatives being unsprung weight. As long as overheating is not an issue, thicker rotors will be an overall net negative.
I have tried trp 2.3 mm 203 rotors with copper metallic pads on my Jeckyll it works pretty much the same as the 1.9 mm floating rotors on my trance x 29 with ceramics, Jeckyll has codes RSC trance has SRAM db8's.
Well, he did say it is about heat dissipation (less fade), not more braking power. Go to larger diameter rotor if you want more power.
@@garyking508 read my comment again. I didn't say that I wanted or expected more power. I said that theres no benefit to be had from thicker rotors, other than them being a bigger heatsink. But youll gain ~100g of unsprung weight!
So ill repeat myself:
"As long as overheating is not an issue, thicker rotors will be an overall net negative."
I am already on 220 mm discs, but they are normal sized 1.8 mm thick...
@@LaurentiusTriarius if DB8s work pretty much the same as your code RSCs, something's wrong with the RSCs my man.
You're right that overheating is not an issue for everyone - same as unsrung mass. Who makes the 220 1.8 rotors? I haven't seen those
You can straighten thicker rotors more easily as well
I have Shimano ice tech rotors from 2015, they are way too thin, the rear one is rubning but there's nothing we can really do about it, the mechanics at the shop have tried, you try to straighten it and it just ends up bending the other way and rubbing on the other side instead.
Also rotor wear. Thicker ones will last longer before getting too thin for the brakes to actually work.
Also even if your rotors
I wonder if the 2015 rotors are much different from 2024 rotors? I don't know the answer, just curious
@@mtbphd according to the mechanics, they made them a bit too thin.
It supposedly helps with cooling since there's more surface area for the volume but being so thin coupled with being 2 piece rotors makes them really hard to straighten out.
Why not black rotors. The dark color will release more heat. Even where not contact with the pad, a painted surface will help radiate heat. Yes, the dark color will radiate more than the paint insulates.
Interesting. Never thought about it! Galfer Disc Wave rotors are painted black in the center.
I could be wrong, but my days working in electronics a million years ago tells me that black is better at absorbing heat from light. I don't think color (or black) makes a difference in releasing/dissipating heat. In fact, on a hot sunny day, black may be counter productive because it's absorbing heat from the sunlight. ..just a wild-ass guess.
I am just hobby mtber, but I am nerd so this channel is best find for long time =)
Welcome my fellow nerd 🤜🤛
bigger on the front is a good idea just look at motorcycles 300mm on the front and 240mm on the rear as you brake the weight transfers to the front
Bigger rotor on the front doesn't make sense in MTB since riders brake more with the rear brake. On motorcycles and road we get higher brake power with the front brake so I can see the argument for motorcycles at least
@@mtbphd CRF450R 2024 Specifications Brakes FronT Single 260mm disk Brakes Rear Single 240mm disk THIS IS A FULL ON MOTO X AND ITS IRELEVENT THE MODE OF TRANSPORT THE PHYSICS IS THE SAME
@@wraith600original1You might like this podcast episode. It's all about why most MTB riders don't use the front brake enough. Also gotta keep in mind that a lot of braking in MTB is to avoid going faster, rather than to slow down. Big difference in how the brakes are used open.spotify.com/episode/5yvyi8mTBcy4JrckHDZ3zx?si=yhXI-6juTdWjYiUU_ulBOQ
Nice one!!
Cheers bro 🤜🤛
Better make a research video if radiators on disc are more important than radiators on pads or vice versa.
I have wondered this...
i stopped the video at 3:16 when you said that there are people that didn't upgrade to bigger rotors because they think there is not enough ground clearance but they are ok with a dirt scraping 12 speed derailleur.... i know two S companies that make a lot of $ from these people...
Totally. I also struggle to see the value in expensive chain danglers
That's a great topic, but the design of your experiment seems rather basic for a Ph.D. level scientist, as you mentioned yourself. It would be truly interesting to see measurable data on how it affects braking power, the amount of braking before fading, cooling down later, etc. Also, having proper control rotors, which are also new, would be valuable. Investigating the hardness of the ZTTO rotor, measured in HRC for example, and comparing it to branded ones could provide insights into its longevity in a long run.
Totally. Unfortunately there's not enough appetite for that level of analysis on TH-cam so the video wouldn't really get seen.
@@mtbphd true talk, bro! Mainstream is more about grimacing tiktoks, whyle channels which are really into deep stuff like Volfsprung or Love.bike (some neardy stuff about chemistry in russian) are getting just tens thousands
Mine is too thin my gf says.
But I never had problems with my brakes. 😂
Plenty of bolt-on options my dude ✊
I have as I call, pornography of brakes: slx 7120 levers, mt520 calipers, zee finned brake pads and 2x ice tech 203mm rotors, best brakes I've had so far. On ebike with total riding mass 124kg, works very well.
Can't go wrong 🙌
Yup
👌
For the sake of learning to be a better rider, and simple curiosity, I’d like to find a way to make observations like this on my e-bike. I am especially interested in the possibility of abs systems with large diameter thick rotors on MTB, both traditional and electric. Awesome video btw, I’m learning tons here.
Thanks Paul. It would be awesome if you got into doing some experiments with BrakeAce - the MTB world needs more!
whoa i didn't know people use braking loggers
New tech mate! I'm a bit biased but it's pretty rad 😁
Bike industry says we need to buy more stuff again.
Nah you can ride thin rotors if you want
Don't buy Chinese made Shimano disc rotors, why because that are only 1.7-1.6mm thick and the two sets I purchased from the bike shop were only 1.6mm. When I questioned the bike shop they had no answer, only to say that is what Shimano Australia supplied them.
What's the problem, simple stamped on the disc is a warning to replace the rotors once the reach 1.5mm, so you only get 0.1mm of wear before they have to be replaced.
The Japanese Shimano rotors are 1.9-1.8mm thick and they also are stamped and state they should be replaced when they reach 1.5mm thick.
I have dumped Shimano and gone with 203mm Tektro rotors that measured 2.0mm thick and are also stamped to be replaced when they are 1.5mm thick. They were half the price of the Shimano Chinese made rotors.
Now that I know there are such a thing as 2.3mm thick rotors I did consider buying some however a note of warning. I have read that they should be to be used with calipers that are designed for 2.3mm discs. With that additional cost it is not worth the added expense as I only do XC and any down hill sections are only short descents.
Yikes - that'd be weird to have varying thicknesses. To be fair I should get a batch of these and check them
calipers use a piston to contact the rotor. as long as it fits between new pads and the surface area covers the pad area... you are good. the idea that the caliper is designed for a smaller thickness but has physical room for a larger one just doesn't make sense to me.
What are your top three websites then? Or your top 10 if you have that many? I like rim brakes. Work for me and easy to work on.
I was hoping somebody would catch that! Haha. Don't actually know the answer... 😁
Some caution should be advised I think. Some forks and frames can only go so big on rotor size and some calipers may not be compatible with the thick rotor trend also.
Cheers
One more Ali express question: I find it difficult to find specific items. Have you found any 223mm or 246mm rotors or Ali express?
Nah not that I know of
It amazes me that the bike industry is trying to recreate the wheel with brake size, thickness and power. As a former road racer and sport bike motorcyclist for nearly 30 years and mountain biker since the late 80’s, it’s well understood that better braking comes from larger and thicker rotors. Rotors that are drilled and float as well make substantial differences. The mix of steeper descents and faster speeds warrant larger thicker rotors 200mm and larger, where’s the average enduro, XC or trail bike will be best suited with no more than 203mm to 160mm rotors. It’s hard to take all this data collecting serious for something that is I’d say common knowledge in other communities. Anything over 200mm on a trail bike is overkill. Also, I’ll note that your info speaks nothing of the gyroscopic forces that come into play with rotors larger that 203mm.
MTBers believe light weight is the way. Fortunately other communities don't have this issue
@@mtbphd I've found this to be true with the mountain roadie types.
💪🚴♂️👍
🤜🤛
Too thin and it has no feel. Too thick and it doesnt enter in the caliper... 🤔🤔🤔
These fit all good. Not sure how those new 3mm thick rotors would fit, but I suspect new brakes will all be designed for thicker rotors from now on (since it makes sense and always did!)
twenty years ? lol dude you dont look much older than 25.
as to thicker rotors ? rubbish
I'll take this as a compliment lol
Do you really say innovative like that?
I've been in NZ for 10 years, so yeah lol
@@mtbphd please stop
End game is RIM BRAKES. The "Disc" is a whopping 698.5mm and 56mm WIDE with air cooling within the rotor. 🦾
Sure don't miss them lol
Magura and trials 26 rims
And you grind through a key structural element of the wheel with every brake appliction...an element that is expensive and difficult to replace, and fails catastrophically (at least if you're willing to concede that an instant flat tire is catastrophic).
@@xanthoptica most rims are made ultra light, but heavier duty rims work very well, and it's not terrible to replace them if you have good nipple and spoke components. Discs are easier to swap, but rim brakes still have a place for low cost and hardiness for most riders.
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