Tyre Pressure Science! How to save 74watts (@40kph) of losses in road TT triathlon
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- เผยแพร่เมื่อ 29 ก.ย. 2024
- PART2 is now out here: • Tyre Selection Science...
Save up to 74 watts of losses by paying attention to the science of bicycle tyre (aka bike tire)! If you doubt you could save 74w try putting a old worn narrow almost flat tyre on your front wheel and tell us how you get on! [most tests carried out at 40kph]
Savings are: 10+13+27+20+5+3+6=84w but I took off that first 10w and it is mutually exclusive with the 13w.
links:
Tyre Pressure Calculator goo.gl/QoMv5P (google account needed)
or APP for mobile phones is here: goo.gl/UevARb
Please check out our training plans on fft.tips/peaks (or www.cyclingapps.net/shop/shop-front/). Part 2 of this video: th-cam.com/video/2Ps4dfgxGAQ/w-d-xo.html Part 3: th-cam.com/video/CqwFz8z7nsM/w-d-xo.html
These are materials that can't be found in Romania at all !!! Bullshit ! 😡 That's why , we roumanians, we stole bikes from Europe !!! And we can't do maintenance on them cause of ridiculus corsts of them !!! On short: To Hell with stupid ecology !!!
15:35 You're so wrong on tire weight. BY ALOT !!!
If I lost 74W then i would be riding backwards
Daniel M good one.
@@carlos.5290 good one
you mean upside down
😂😂😂
🤣🤣🤣
Probably the most educative video I've watched in a long time.
Thank you.
Optimal tyre pressure is calculated for a given rider + bicycle weight and It depends on the air volume (i.e. tyre width). Optima pressure for 23 mm wide tyre isn't the same as optimal pressure for a 25, or 28 mm wide tyre.
So a 100 kg rider with 23 mm wide tyre will have a different optimal pressure than a 60 kg rider with 23 mm wide tyre, or a 100 kg rider with 25 mm wide tyre.
How to calculate optimal pressure:
www.bike.bikegremlin.com/2015/12/23/pressure-i-inflate-bicycle-tyres/
Good video - lots of great information. Would have liked the data to be presented longer instead of flashing it on the screen. More time is needed to see and digest the numbers - had to pause often to look at data. Thanks for your summary and presentation!
Thanks. we do this intentionally to reduce the total length of video. Get ready for the pause button again this weekend. New video coming! ;)
Thanks for the video, great detail explanations!
I only have 74 watts.
Maybe one day you could cover tire width relative to wheel depth in terms of "power savings" assuming the tire width and rim width are equal.
Now I get it. You made this video for your Thesis exam. What I don't get is, who would be silly enough to ride their road bike with 45 psi in the tubes. Hello pinch flat.
Hi, great video, very well explained. I'm just wondering why some of the biggest tyre brands didn't make it to the test/comparison (Vittoria, Michelin)?
Most likely because they haven't put their data from aero or CRR in the public domain (unless I missed it)....but didn't I give I shout out to Vittoria at 3:20 for their awesome graphene additive?
Radim Vavrecka Veloflex
Wayne Proud: Veloflex and Vittoria is actually same shit. Vittoria moved their production to Thailand, then some of the old Vittoria-staff re-opened production in the old facilities in Italy and branded it Veloflex. Said to be good tires, though.
They are much better than good. They are brilliant and if you are patient, can be got in bulk during sales. So instead of £58-65, I got 5 of them for £44 each .
Did some work on trying to create a tyre pressure spreadsheet myself a few years ago. Using bike weight + rider weight + weight distribution. Wanted to use tyre volume rather than width though to get it to work across road and mtb. At that point my rusty physics and maths started letting me down. Would be interested in your view to this approach.
Have a look at both XLS spreadsheets for tyre pressure. The volume one is a bit complicated. Do you think it is useful to have the exact tyre volume?
Hey guys, in the spreadsheet, rider weight is naked weight or full equipped rider (helment, clothing, shoes, etc)? Also, bike weight is with or without bottles, gps computer, saddle bag?... Thanks in advance
Thanks, a well researched and presented video with good empirical evidence, nice one
Wouldn't it be impossible for anyone to actually save 74 watts?
I'm thinking you could be under-inflated (and save 10 watts by correcting) or be over-inflated (and save 13 watts by correcting) but not both?
Maybe I am too hung up on the video title? The information was great and thank you for sharing, I'm just wondering if maybe a few more of these items would be mutually exclusive and the total potential savings of following all prescribed tips would be 61-64 watts of savings (depending on over/under inflation). Thinking out loud here as I am relatively new to the sport, my bigger question is:
What would one have to invest in dollars, in their wheels, to save these sixty-some watts?
Thank you
You are correct see 22:20. Regarding the costs the saving range from very cheap to very expensive....law of diminishing gains.
I like the video, but I don't agree on adding the losses for too high AND too low tire pressure :) Also, for the rolling resistance the estimated speed between 0.003 and 0.005 @80Kg system weigth is about 60km/h.. but still a very nice overview.
Nor do I: see 22:20; (10+)13+27+20+5+3+6=84w and then I took off that first 10w
Oh, I'm the 2nd person to ask.. thanks for the quick reply. After watching the climbing vid I'll have to calculate the strategy at the bottom of the hill now :) Maybe it could be a good option for GoldenCheeath to generate a target power curve with total exhaustion at the end of the track.
Any thoughts on regular spokes Vs bladed spokes Vs disks
Very useful information! Thanks!
But you missed a big one: an areodynamic shell. Get yourself a Milan Velomobile, a decently fit rider will beat the hell out of any TT Champion. UCI? UCI who? :)
Boy no wonder am so slow.. I could save up to 150 watts on my old beat up bike I can't wait to buy a good bike
On my road bike I found compound is everything. However when my 23s wear out I'm going to see if I can't fit 26mm. My touring bicycle has 47's and it rides like an SUV. However those particular tires weigh nearly a kilo a piece and they are bulletproof.
For those who got it right and watched the video, sorry that's all you get.
nice video. just one question. i am having difficulty for choosing a aero wheelset between ENVE and ZIPP. what would you consider the best wheelset. thank you very much!
Very difficult question. Which model? Have you seen this comparison: th-cam.com/video/JlhBZC5dRNI/w-d-xo.html
yes i have seen this. im going to buy a clinch wheelset that is about 50mm high. there are many options out there i dont know which one is fast. i hope you can give me a suggestion thank you!
any wide torroidal model made in the last 2 years should be fast (of course with aero spokes) from zipp, enve or FLO. The deeper the wheel the better for aerodynamics but worse for control in wind gusts.
Jiehua Huang i would go with enve, zipps hubs have known problems and have had recalls plus they are flexy. Enve do have a problem with corrosion on the concealed nipples but it is easy to inspect and replace.
Jiehua Huang the new zipp 454 nsw's maybe better but time will tell
brillant
Not accurate #6 Tyre Weight 00 watts - Heavier tyre makes you pedal harder than lighter tyre. It is the same scientific fact about heavier rim needs more energy to rotate it every time.
Very informative, but too fast in talking & in presenting background data. Will be better if you slow it down since audiences are not the same and native in English.
Will be nice if you can delve into mtb too.
Fadil Aziz i believe youtube provides a setting for you to slow down a video playback speed and also subtitles. Maybe that would help you ?
Yes he does talk fast but i believe that was self explanatory due to his channel name. “Fast fitness tips”
youtube player gear icon - choose playback speed 075 and you have your slower presentation. You'er welcome.
Fadil Aziz Yeah. Maybe next time ease up on the coke before making a video.
Am I the only one who thinks in the Fast Fourier Transform when see 'FFT' instead of the name of the channel?
Pablo Briz you might be the only one with that acronym!
@@Fastfitnesstips I did elec eng. I thought it too.
Me too!
You can't have a too high and a too low pressure at the same time. So why would they be added up?
Because clickbait.
My bike has two wheels so you could.
You didn't watch until the end or added it up did you?
Great video. But what about these:
-Wheel truness lateral
-wheel truness radial
-wheel dishing
-spoke tension?
All Variables that play a part as well. Rotational weight, Hub LP vs HP, bearing efficiency,
Are we also going to include fork dynamics with the wheel ?
The same wheel in different forks with different tyre clearances, shape of the fork, angle etc
duh, moisture in the air and road surface?
"Paris-Robaix Training Wheel" at 4:00 gave me uncontrollable laughter
Can't thank you enough. Terrific video from a variety of sources wonderfully dissected and summarized. Would love to have had access to this data when I raced TTs many years ago. 18 mm tubulars pumped to 160 PSI -- ouch. Makes me wistful though. Reminded me of Bob Seeger's line in Against The Wind: "Wish I didn't know now what I didn't know then" (smile).
Thank you for the great feedback!
Matching tyre width to rim width will have an impact on aerodynamics as well. Putting a wider tyre on a narrow rim is actually going to increase the drag. Not sure if you touched on that. Interesting video
Quite true thanks!
Rixter i believe this whole wider rim thing is more about changing the shape from a teardrop to a more round shape to copy a tubular profile. To me Tubulars are still the gold standard, ride them they are lovely. changing the shape of the tyre will make it proform different. Remember that with clinchers you can't just put wider tyres on a smaller rim as the tyre shape changes, why the wider rims for wider tyres. With tubulars it doesn't make any difference as the tyre will always be round.
These are materials that can't be found in Romania at all !!! Bullshit ! 😡 That's why , we roumanians, we stole bikes from Europe !!! And we can't do maintenance on them cause of ridiculus corsts of them !!! On short: To Hell with stupid ecology !!!
Haha, I was going to write you that you made a mistake by thinking that it's possible to commit the too high and too low tyre pressure mistake at the same time, but at the very end of the video you noted it that it's either one or the other. :D
"Rolling impedance" is my wife telling me to mow the lawn instead of riding. "Rolling resistance" is belly fat.
I'm in shock. I just used 74 watts to get all the info in my head. How it's possible a human brain be able to store so much information? Jesus !!!! Thank you for sharing the video, now going to watch it a couple more times 👍👍👍
The Paris-Rubaix training wheel had me laughing out loud for 30 seconds. 🤣I nearly missed it and had to scroll back to see it. You should’ve left it on screen for longer. 👏👏
sad state of affairs where bicycle industry marketing companies are defining physics instead of physics defining physics...
Almost every single point made here is based on research done by parties with vested interests. I saw a few formulas splashed on screen, but I didn't see you going into any of them.
things like the friction between the inner tube and the tire being given a figure like 5 watts and all these shenanigans about wide vs narrow, ignoring that the vast majority of aerodynamic resistance comes from the overall frontal surface area just make me sad. The benefits from a wider rim come primarily from decreased deformation at the contact patch (as the contact patch approaches circular, the total volume displaced decreases, thus reducing rolling resistance), but it comes at the *expense* of *WORSE* aerodynamics. Something like 80% of the aerodynamic resistance comes from the total frontal surface area. So if the frontal profile increases in width from 21mm to 28mm, you've increased the total frontal surface area by... 33%
Yeah, you just increased 80% of the aerodynamic resistance from the wheel by 33%. And reduced it at a few angles of yaw wind for maybe a few percentage for a small portion of the rim circle... for the turbulence drag, which is 10-15% of the total drag...
Not to mention Paul Lew's argument about the Reynold's numbers of air not matching the "data" being pulled from things like the Specialized "sciencey labby wind tunnel marketing BS generator".
most of these factors are a few percent of a few percent of a few percent. Not 5-15 watts, more like 0.000015 watts. And certainly not 74 watts.
Things like tape along the edge of the tire and rim are common sense and there are two reasons they aren't found anywhere: #1 - they make almost no difference at all in the real world and #2 - Mavic likely has patents to protect the idea.
The principle is sound. But even F1 can't be bothered to tape up their tire-rim edges and they are traveling at much higher speeds. As the speed increases, so do the potential benefits of any aerodynamic improvements.
And while some wheel aerodynamic improvements do help more than anywhere else on the bike because the wheel is moving faster in the top half than the rest of the bike, the sheer amount of other places where turbulence is occurring is a sure-fire way to tell that this advantage is near-infinitesimal.
Don't believe it when cigarette companies tell you smoking is cool.
Don't believe it when bicycle companies tell you their wheel (which is 99% identical in shape and frontal surface profile to every other wheel) is XX Watts faster...
Thank you for thorough input. Any thoughts on tyre impedance? Any other things you feel should be the focus for easy marginal gains?
I would consider his science to be equal or superior to yours, given actual measurements and images, versus your luddite anecdotal contrarian statistics. A number of his studies are not by individual companies, so do not automatically presume a sinister, nefarious bias solely designed out of thin air to sell us something new. I am generally as dubious as the next person when new "greatest ever" breakthroughs are touted, but this cuts through a lot of the clutter. By the way, he clearly describes how and why the total area of a contact patch is always the same for equal psi, and you fail to grasp that - the total volume displaced in the tire must always offset the load weight (excluding the minimal offset by sidewall stiffness). 180lb / 90psi =2sq in. independent of width of rim, tire, profile, etc.
My feeling told my that Conti 4000 S2 is great tire. Best I ever have. And it is not just rolling resistance. It is about comfort and cornering. Maybe there are better tire for me, but I didn't found them. And Conti lie about width. My 23 are actually 25mm, and 25 are 27mm. So there are not perfectly fit on my narrow rims. But my rims are old and heavy just like me. No tire can fix all that problems.
The GP 4000 are a good tire until the sidewall blows out for which it is known for. It happened to me when I took a corner. Even though I am a Clydesdale, it should not happen.
Rak Rakovica gp4000 are great all round tyres, but are not that comfy. if you ride top level cotton or silk tyres you will see another level of comfort.
massive case of theory not adding up in reality. You cannot make a 74 watt saving just with subtle changes to road wheels. If you add up all the potential gains from a skin suit, aero helmet, shoe covers, optimal body position and aero frame, I would save 150w. That means I can go from being a hobby rider to dropping chris froome. Not happening. This just doesn't add up like that in the real world, maybe I can save 15w at 40kmh.
I think if he laid down the facts with a nasty beat, wore a Zoro mask, and flip flopped on supporting and opposing con artists like Durianrider... then you might have liked the video more.
Beyond that, VegtableFootsoldier, you are an idiot that makes clown videos, filled with hyperbole. Good on you.
The assumption is that (with the right training) you can put out 80% or 90% of the power that "Froome" can put out. Which isn't that hard. The hard part is doing it during the Tour at 98%+ when your rivals attack you.
he should save 74Watts in speaking tempo. Much too fast.
cause its not like you cluld adjust that on youtube right?
If its good enough for Fabian Cancellara, its good enough for me!
This was a great presentation. i notice on my e bike when my tire pressure is 10 to 20 psi lower than it should be my max speed goes down almost 4 mph. You are a great speaker except that you talk extremely FAST. Especially for speaking english . I can picture someone learning english listining to you you must sound like a machine gun to them lol. Spanish can be spoken fast like that so naturally. not to often i hear english spoken so fast lol. great job tho.
Thank you for the feedback, presentation rate is slowing down on more recent videos!
You can either have a tyre pressure too high or too low so you cannot add them. Good overview about possible power savings or losses, respectively though.
I was just thinking the same
Exactly! Very useful otherwise.
He didn't add them. He said you can only have one or the other.
He was telling that he was not doing that at the end.
it can happen, say you're running on different surfaces on the same run.
Yep I know when I've pumped my tyres too high. I get this fantastic 'popping' sound. Damn it !!!
nice video. I like seeing all the supporting data. Thanks for this.
at speed over 15 mph, resistance from the body dominates 80%. Learn to mod the body. Also, tire performance is more than just rolling resistance. Cornering matters. Conti has great rolling, but it's shit in corners. Faceplant in a corner is not fun.
Great video but... surely you can't count tyre pressure savings twice? You will save energy if your pressures are too high, or are too low, but pressures can't be too high and too low at the same time. Ergo max savings are 61-64 watts
You are correct see 22:20; (10+)13+27+20+5+3+6=84w but I took off that first 10w
Spirit in the sky
Ha ha ha ha ha ha ha...
although unlikely, you could have different pressures at front and back, in which case you average the savings. Plus, if the weight is not evenly distributed, inflating the front less should be the case. What was not mentioned was the turbulence caused by the thread of the tire. Also, the droplet shape works when the front of the tire meets the air. It does not work when the rear of the tire meets the air. Another thing not mentioned is the turbulence of the spokes as the rotate, which like the thread work against you. Finally, do not forget the mudguards. The turbulent airflow is compressed between the tire and the mudguard, causing further resistance.
Yeah I do agree... There are 74 watts can be saved but it doesn't mean we will go 74 watts faster. Nice video though, very informative and very useful.
Great video, bookmarked! I do have a problem with the prevailing idea that wheel weight doesn't matter though (the maths and the explanations don't make intuitive sense to me at least!).
1. driving a car in town you get hideous mileage, I get maybe 2/3 to 3/4 of what i get bombing along UK A-roads. If you watch your litre/100km dial you see the massive amount more energy required to pull away. Remeber this is in town never going more than 30mph (kinda!), even when you have to brake down to 20 then gently raise back to cruising speed it drinks a lot of fuel. Bike speeds and accelerations are really not that different in town, in fact, bicycles usually pull away for the first 10 to 20 yards. When you compare the power to weight ratio of my car for example; 151kW/1650kg compared to me on my bike @ 300W/85kg, makes me wonder how energy sapping those fractions of a second (don't believe that) are and how they affect the overall ride time.
2. The explanation of the racer who used the heavy rims (a) he's racing not riding around town stopping and starting and (b) if your wheel contains enough energy from the weight of it's rotational force to roll you up a hill, then that has to be quite a lot of energy in that wheel there!? The argument that once the wheel is going then that energy is always returned is bunkum, it disappears as heat in your brakes every time you hit a junction or set of lights, and it's fighting gravity every second you have that energy built up in your wheel.
3. I don't have much faith in that Alex Simmons comparison with the different weighted rims either, (a) the heavier wheel was more aero than the lighter wheel so you have two variables there (b) the test is short doesn't expose how much of a difference these increased efforts to overcome inertia may have on an overall ride (c) the difference of 250g is quite negligable where it is easy for some people to save 1000g by upgrading wheelsets if they're currently on beasts like mine (d) the numbers were generated by a theoretical formula, I have just been reading a piece about a solar-powered water-purifying device which (bear with me) the efficiency exceeded the theoretical yield, it's a rare thing but there are plenty of unrefined formulas out there.
If this is all confused bs could somebody pls put me straight, before I go and spend dollar on some lightweight wheels!
A good explanation from another cycling scientist (th-cam.com/video/0QDnUkUaQfk/w-d-xo.html). But you are right. The moment you break you loose the flywheel effect accumulated on the wheels.
Wowzers, lots of good info, I’m glad I’ve got the contentental 5000 25’s that I run at 70 psi and yes I do feel them ride fast on my carbon Roval 35 rims
70 psi on 25mm tire, are you kidding me? you should be around 100-110 depending on weight lol
Great speech, need more people like you, not text screens after camera
Thank you!
Next save 120 watts by fixing your rusty chain and rubbing brakes
I like the data collections but the rational could be tweeked much more.
1) you can’t have too high and too low tyre pressure. It’s either one. So add just one.
2) Tyre weight differences is truly insignificant but if tyres were significantly heavier, the effects would speak in long steep climbs.
I would still give a thumbs up.
How many words can one squeeze in a minute? now I have all I need about about rolling resistance and two less paracetamol tablets in the cupboard
Holy shit , if I implemented all of these savings I can ride a perpetual motion machine that moves forward by itself . . . Amazing math
very funny!!
To your credit. The hidden motor still stands. Pretty obvious
i love scientists, you did not even try to explain the difference between tubular and clincher, jet i understood within 5 seconds, while other people failed to explain it... Scientists have just so much cleared thoughts and expressions, love it great video!
I wonder if I were to use "baby powder" between the tire and butyl tube to reduce the friction?
5:30 "Wow! That's amazing." *awkwardly point at air* I died of laughter. So cute. Good video, pardon my amusement.
dude you forgot Vittoria who make graphine+Kevlar Reinforced tyres and their best tyre the corsa speed which is the worlds fastest tyre.
3:19
thanks missed it
What about the effects of using sealant? Extra weight vs. savings from no flats? I switched (back) to tubulars last year + sealant. So far, zero flats - even though I have a hole in the rear tire which doesn't loose air because of sealant.
Very good question. I don't think anyone has tested the watt loss of the sealant. Its not really about the weight its likely about the intertia of the sealant and maybe rotational weight. I'd love someone to do a spin-down test with and without sealant. Apparently they add about 100g (see www.slowtwitch.com/Products/Things_that_Roll/Tires/Sealant_Test_-_Part_2_4155.html)
Interesting. the sum is 84W, you wrote 74 because saving tip #1 and #2 can't exist together isn't it?
would be nice to have the same analysis for mtb tires and usage.. i guess less savings from aero but more from right combination of compound and pressure. besides all we are not considering the more confort large tire + low pressure give = more energy= higher average power or more cornering grip=faster turns allowed
Gabriele D'Alessio Something that isn't talked about much but is a real thing is sail effect. Wheels with a deep flatter profile change crosswind forces into forward motion, i.e. like a sale boat. the designer of the reynolds rzr wheels talks about this. I think it is a trade off though with buffering from side forces. Riders don't like this so want more stable wheels. Alot of the design today is to prevent this, not to provide forward motion.
Will putting talcum power around a butyl tube reduce the friction between the tube and the tyre and therefore save watts?
Interesting, quite possibly, and it could also reduce pinch flats. Nice idea! Maybe someone has tried this and can comment
Rixter this is something I do religiously. Not sure if it reduces friction as I have heard, but l believe it at least keeps the butyl tube from aging too fast and failing.
Rixter yes with talk powder you will lower that friction between the tube and the tire as talked about 13min in to the movie, specialized does this extra to their premium tubes to become as efficient as possible. As a bonus it also becomes less prone to pinch flatts.
I like that!
Fastfitnesstips I use chalk all the time, I run too low of a pressure and feel like it helps not pinching it
I weight around 48kg, I usually go for 60-80psi, the group i'm with used around 130psi! But yeah, still got to drop them lol
You should be able to trade the 74 watts you saved with other cyclists for inner tubes like those carbon credits
Ceramic and hybrid ceramic bearings definitely save a considerable amount of energy, but how much depends on the OEM bearing seal type, ball grade, ABEC precision level, ceramic ball type, race material, and type of lubricant. I even have data that shows a tungsten disulfide coating applied to bearing races will save up to 5w. I sell hybrid ceramic bearings for ebikes that improve the range up to 20-25% with the full kit and a *lot* of data to back it up 🙂
I have seen tire size go from 700x26mm up to 700x38mm. They say this is more efficient because it saves on road chatter. So what would the optimum width/pressure be?
Cant say without knowing your riding type / weight etc.
I have a Hybrid and ride rough paved country roads weigh 230 lbs. I was going to upgrade my cyclocross tires from 700x30 to 700x35 (85-90psi) to get some better handling for dirt/gravel. I was just wondering how much this would increase effort over all.
I was also going to switch my road bicycle from 700x28(120psi) to a 30 or 35mm width maybe with lower pressure. The back roads here have a surface texture for anti slip in winter(rough surface).
For road 28mm try 92 psi F and 104 psi rear; 30mm 81 F 92 R (35mm...check you have clearance in your frame....quality of 35mm not good for CRR see th-cam.com/video/2Ps4dfgxGAQ/w-d-xo.html). For hybrid if you do go with 35's try 55 F and 63 rear for gravel road. Download XLS in the description and try your own combinations!
Seems like mavic know a thing or two when they desiged their cosmic pro wheel/tire combo.
You completely lost me after talking about tire pressure. The same guy you cited as your source while working at Zipp has a tire pressure calculator (Silka or something) that shows for me, 28mm tire at medium to high recreational speeds on normal US crappy roads and GP5000’s with tubes is around 75psi. Who tf is riding 100-110 PSI in 2022? Not even on 25’s would I be doing above 90-95.
Man, the hand and arm waving are a distraction from the message. Nonetheless, the roads in Sarasota Florida are like Paris Roubaix and I have to run not more than 45 lbs. It actually broke loose a filing.
So to be loosing 74 watts you would need to be running a terrible narrow tire with a crappy compound, which doesn't mate well to the wheel and they are over/under-inflated. Seems legit.
The only problem with tubeless tires is that the sealant used is only good for 3 months, after which you have to add more sealant which will increase the weight of the tire which supposedly hurts rolling resistance, but you say weight doesn't affect it.
On my touring bike, I had tires that weighed 1000 grams each, I switched to a 550 gram for each tire and there was a noticeable improvement in the speed of the bike.
Saving #6 the data is completely wrong, for that you would need to head back to college physycs and re learn a few things. 1) tyre and rim weight play of all the most crucial of roles, even with only 50 gr differences you begin to notice diferences. For example, if there is this kid 20 year old, fairly well trained, not a pro, with a body mass of say 78 kg, using a pair of regular aluminum rims placed at say 1950 grams a pair, and perhaps opts for 300 gr tires and say 125 gr inner tubes, against one well trained 55 year old same physical characteristics, decides on the following, 1250 gr a pair rims, makes sure the weight is mostly concentrated closer to the hubs, decides to use 200 gr tires, same size, and inner tubes at 50 gr.. well that poor soul of a kid is in for a real beating on uphills, flats, and sprints. Because the forces needed to move those completely diferent wheel sets, are in total disadvantage against the kid. And the more time goes by, the harder it will be for the youngster. The sheer moments of inertia diferences go well beyond 30%, the rolling resistances due to the weight differences are complete opposites. Make a simple diagram as in a physycs dinamics exam, a circle of such mentioned masses and figure out the work needed to move that mass over any incline over a period of time, worknout the force needed to accelerate each set, make sure u use the actual diameter for your diagram, you will then, head out to your nearest store, dump your old inner tubes, your 280 gr to 300 gr tirers, and your 1950 gr wheelset, to never ever use them again, and will now marry the second option. There is no way around this.
Just like you can't add saving #1 and #2 at once, you can't really do that for #4, 7 and 8. Because 4 and 7 are a direct result of 8. Or you can't really separate the results of wind resistance from rolling resistance because of shape, unless you do the rolling test in the vacuum.
Was going to say the same. Savings #1 and #2 are a bit more obvious though. You tyre pressure can’t be too high and too low at the same time, it’s either too high or too low so your watt saving is one of them, not both.
riding my old mtb on the roads here it seems to be best between 50 and 60. beyond or below and I get the issues you described. good info!
Did this and now I don't even need to pedal most of the time!!!11!!!1!1!!
Difference in tire width on energy loss to smoothing your ride on rough terrain? I suppose muddy would be best to ask off road riders though. Wider resists better sinking into and being grabbed by loose or somewhat fluid materials. Narrower is probably better for handling on pavement.
Didn't actually say much.. still don't know what the things are I need to do to save watts! List them please... together... simply.
HED do research into this, it's well worth watching what they say about pressure and how it relates to rider weight, tyre and rim width, as well as riding surface.
Great information, You answered some many questions, Thanks for the fast pace, you kept me engaged. I will recommend you're video to friends. Now I'm off to the tire store.With knowledge.
thanks but check out some of your more recent videos! like fft.tips/vsurface
Wow great content! Did you study aerospace/aeronautical engineering at Uni? I do physics A'level and am seriously impressed with your understanding and knowledge (way more advanced than my course)! Also the language you used was very good not just those buzzwords that GCN or bike radar just throw in whever they talk about tech
Thanks I did physics and maths A level and medicine at Uni! I agree its good to avoid jargon as much as possible and keep it practical or applied to the actual riding/event
Not sure if sarcasm or not.
What happens with efficiency if you put oil between tyre and tube. Not much only so that they don't contact each other directly? In theory frictional losses disappear and there are only fluid losses.
oh mine i like your painted jokes but can u hold for litlle longer i mean around 1,5 sec meybe 2sec and ofc science pictures too ?
haha they are there early for those with a short attention span!!
baca zterchovej pause
What about tire balance. I see most tires are 5 to 13g out of balance. I balance mine and they have less shimmie and a smoother ride.
Too bad I can only give one thumbs up - awesome summary!
Even citybike tyres use less than 74 watts at 40km/h, so it's clickbait
You are incorrect to say 100-110 psi is optimum without describing the tire width
You can't count watt loss from both 1. and 2. Either you pressure is too low or too high, but not both.
4:34 Rolling impendance or impedance?
I could save a couple hundred watts if I could keep my pie hole shut for more than a hour!
You are double counting some of the watts.... You can have a tire that is both too high pressure or too low.... That has to be one or the other....
a beginner ride is averaging 200 watts ? Let's be realistic here, beginners far less than that. 8:30
lol, untill now, ive been running 23's at 145 psi! fail.
Tyre and rim combine can be compared to the leading edge and wing of a aircraft deployed and retracted.
thanks for adjusting the psi with the weight but just to be sure that I understand the formula correctly, +2 psi for each 10 kg = +1 psi for each 5 kg right?
best to just follow the formula as not all the calculations are simple linear addition. thanks.
Josh Poertner is and has been an incredible asset to cycling. Absolute legend.
You may want to update your video. Wider rims and tires, especially running tubeless, and your numbers are flat wrong on tire pressure. My new HED vanquish pro recommend 70psi from factory.
Good shout and already done: th-cam.com/video/Zj0s6mTFySw/w-d-xo.html and here th-cam.com/video/CqwFz8z7nsM/w-d-xo.html .
Great video, incredible math show that some things like tyre weight has minimal effect in performance. I'd like to ask you for the power difference between a road bike (700x25 tyres for example) and mountain bike (hardtail 29x2.1)... How much could the speed difference at a given power on a paved road? Anyone has any idea about it? Thanks for your thoughts
Not accurate #6 Tyre Weight 00 watts - Heavier tyre makes you pedal harder than lighter tyre. It is the same scientific fact about heavier rim needs more energy to rotate it every time.
You were talking too fast and showing the diagrams for too short a time and in some cases at a magnification that made them rather useless.
Agreed. trying to cram too much in! Use pause button where possible that might help.
ENERGYsaving is not absolut!! - but depending on speed. If you follow your school "science" all theses saving will have your bike moving by itself since all the sawings are absolut. Get the fysics right before posting.
Get the spelling right before posting.
i ride lower PSI with larger tires which absrbs vibration which was shown to speed you up a lot. Its not about watt savings its about vibration dampening.
you don't lose watts. you lose watt hours. Watts is a power term. Watt hours is an energy term. Re do this video
Very interesting point but in a direct head-to-head comparison, if you ride the same duration doesn't the time component cancel out of both sides of the equation?
It seems to me that this calculation double counts the savings from tire pressure. He says that if you are too high or too low you lose 10-13 watts. The problem is you can't count both. You can either be too high in pressure and come down to "correct" pressure, thus saving watts. Or you can be too low, and come up to "correct" pressure, thus saving watts. Only one condition can apply, not both. So it is intellectually dishonest to count this savings twice. Thus, the savings would be about 60 watts, max.
Wow, did you watch to the end, or read the description or read any of the comments before accusing me of being "intellectually dishonest"?
Great job! I love the way you are actually looking at this scientifically and thoroughly. I like the way you cover a lot of ground clearly at a fast pace - we can always replay if we need to go over something again. My only small criticism is that I think you should have muted the sound of the video you showed at 14:15 because it was a distracting. But overall, a top video! Thanks and I have subscribed.