How Much Does Tyre Pressure Matter? - Testing Rolling Resistance | GMBN Does Science
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- เผยแพร่เมื่อ 9 เม.ย. 2023
- How important is tyre pressure for mountain biking? Does it really matter? Some riders focus on other setup adjustments such as suspension and stem reach/stack, and tire setup can get ignored. But are they missing out on much traction and speed? In this video, Neil Donoghue tries to find out (with a very unscientific comparison).
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What tyre pressures do you run? Do you change your pressures depending on where you are riding?
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Would be great to have a gmbn RAW channel where for example Neil's full POV footage could be uploaded. Looked like a great trail.
Hey! It's well worth checking out our Instagram, Tik Tok and Facebook to get content like this. It's the best way to see more of GMBN. Who doesn't love some RAW ASMR bike footage?! 👊
What hand does Neil clean his arse with?
I'm an XC rider on rocky, rooty, and loose terrain and I've been running 15.5 front and 17.5 in the rear with a variety of Maxxis tires. I just switched to the Vittoria Barzo and had them at 18 front and 20 rear just to be safe because I didn't know them. The grip and rolling resistance were way better than any of the Maxxis tires I'd been riding for the last 10-12 years. However, they felt like rocks with that pressure. I'll gradually work my way back down to find the sweet spot but I'm thinking it will probably be 16 front and 18 rear. I'm a LOT slower than Neil on the downhills but I've always been shocked to hear about his tire pressure and thought it was crazy high. I'm glad he did this video and his findings match most of today's thinking.
Would it be possible to do a video about the effect of tyre pressure on uphill performance?
The truck tire pressure ?
@@nico6305 🤣
For sure! Thank you for the suggestion! That would make a great video. 👍
I'll throw in my experience on climbs in Utah.
I bike with my son (I'm 70 and he's 31) so uphill performance is more important for me. I expect him to wait for me in both directions, but I take it personally on the climbs. I have religiously timed my climbs with different gear, tires and pressures. I'm 160 lbs on a Trance 29, i27 rims, no inserts, usually an Assegai EXO on the front and a Dissector EXO on the back, and I consistently climb faster with 12-13 psi front and 16-17 psi rear. My tech "test" climb is Sweeny's-John's in Park City, Utah. Very Rocky/rooty. The climb starts at 7228' and climbs 1,024 feet. If I ran high pressure, I'd be ricocheting off of every rock!
That same climb to the ridge on the Great Western trail climbs 2685' and it's way slower at higher pressure!
In Moab, The Whole Enchilada drops 7124' and it's no problem (no inserts) at 15 front and 17 rear, but I ride "light".
I wanna thank you for this comment. I’m getting into MTB and I usually hit the trails in PC when I can, so this comment feels custom made for me! 🙏
Great video. Couldn't have timed it better because my first downhill race is coming up in a few days.
Good luck on your first downhill race!
I agree. These runs would have been good on POV - really engaging. A separate place for them RAW is a great suggestion.
The one thing that is constantly forgotten in this discussion is with too low a pressure in the front, your steering will start getting vauge and slide.. too hard you lose the added grip and dampening. You need enough pressure to keep the side knobs as firm as needed.
TPI as well as tire casing are factors in what pressures you can get away with as well.
these videos with Neil testing stuff are so good
One thing of note, higher tire pressures will give you more stability in corners but less grip, lower tire pressures will give you more grip but the tire will roll over more making the bike less stable. Unfortunately tire pressures are one of those things that can be as complicated as suspension setups since every rider, every terrain, and even every day is different. Until you're riding professionally or racing at a fairly high level, don't put too much stock into your bike setup, find something that works and just ride it.
I'm 90kgs with my gear on, always aiming for 24psi front / 26psi rear (Maxxis EXO+ casings). Recently had a crash and cracked my ribs because of experimenting with low front tire pressure (20psi), so won't be doing that again!
I'm about 93Kg kitted up and run exo+ casings. I usually run 22psi front and 25 rear. Pretty close to your psi's.
Good video, interesting test. I’m riding 17 psi rear and 15 psi front. I quite like the lower pressure for the grip. I’m not very heavy, 65kg
Your results make perfect sense to me and in fact I predicted as much. Your times will always be better the more you stay in contact with the trail. A lower tire pressure will of course allow that. Finding that safe pressure keeping you from snakebite as we used to call it (pinching the tube on the rim) is key. Great vid!
23 F and 25 R is ideal for me (170 Bullit + I’m 88kg loaded) Maxis Assegai F DHR2 R. Works great for me, big bike parks or running the loam.
Would be interesting with a video with/without inserts! They really change the way the tyre pressure ramps up much like tokens in a fork. Gives really nice compliance on small chatter and still offers support on bigger hits. Weird feeling!
It definitely matters! Especially on hardtails, I usually run 18-19 psi on my 29er (2.6in wide) hardtail. If I go above 24 psi on my rough local trails it is extremely uncomfortable on me and my frame
Great info! Would be nice to include some climbing tests.
Wow really surprised Neil. Can't believe you run such high pressures and also such similar pressure front to rear. I'm a similar height and weight to you and I run a 5psi delta.
Normal riding at bike park Leeds 20f25r and I bump up to 23f28r for more hardcore trail centres and Ard rock.
Maybe your harder pressures are because you're faster than most and push harder. Be interesting to see if there's a more ideal pressure and delta for you.
Would love to see you do a longer form video of no pedal or no chain runs dialling in what is your ideal pressure for fastest time on a normal riding section.
what is Neil's weight for reference?
I ride mid Atlantic, east coast, single-track. I have hundreds of timed runs on my nearest trail. Pressuse as low as you can go without that side roll feeling has produced the fastest times.
Totally different considerations when having to pedal on flats and uphills. S little lower is better if there are irregularities in the surface but higher is generally better if it's a smoother sirface. We're not all young, light and super fit!
I found 1,5 bar front and 1,7 bar rear to work pretty well in the rough stuff, but for jumps the bias f/r should be more 50/50, as with the mentioned setup the rear tyle tenis to pop up more.
According to Allan millyard high tire pressure and a proper suspension set-up is the way to go. The give in the soft tire will stop your suspension doing its job properly.
When I use my MTB for commuting, I run 35 PSI both. When I'm on the trail, I run 20 both as seems to be the best balance for the majority of tires I've had over the years. When I run less then 20, the tires fold over waaay too easily, rim strikes happen way too much and I run into pinch flats. The road bike - it more depends on the tires, but generally I run in between the min and max recommended - all depends on the feedback I get through the bars (too low my vintage road bike does genuinely feel sluggish and have proved that is the case with timing myself on a few rides, while too high makes my hands and buttski go numb which also slows me down). Majority of tires I've run puts this around the 85-95PSI mark, but my current tires it's 110PSI.
at 108kg's of body mass, I find that I've a smaller window of options available due to physical tyre wall tolerances. I run finger squish and gave up tracking psi in the end.
Hi Neil! Cool video.
Thinking on (rolling) resistance is a bit misleading. The phenomenon is better understood if you think more broadly on shedding kinetic energy.
And what happens is that there are multiple ways to shed kinetic energy that are associated (or modulated) by the pressure on the tyres. Some of these mechanisms have a linear relationship with tyre pressure and some are non linear. Some are direct and some are regressive. Therefore you should not expect the end result to be a linear, let alone a monotonic function!
The physics of a rolling wheel can be deceivingly complex! The internal deformation of the wheel, the relation of the contact patch with the ground (sticky or not), the vibrations transmitted to the rest of the bike-rider system vs the vibrations absorbed, etc
To find the sweet spot you need to test many more tyre pressures in between within your range of rideable tyre pressures to find it. And even then, the seeet spot will vary (probably slightly) between different terrains.
For XC/trail riding I use 20 psi front and 24 psi rear, and I out roll and out grip, all my old school mates with rock hard tires, everywhere but the the smooth tarmac 👌💪🏻🤘
Great content... I'm about the same build as Neil but with much much less mtb skill and this vid has made me look at running even lower pressures than I do at the moment.. currently run 26r 23f - and a bit lower but now I will look at running even lower than that....Thanks Neil and GMBN
Loved this super interesting episode! Thanks Neil!
Great video! Totally confirms how I feel. I’m curious about a timed tech climb comparison. For most of to have a fun down, we need to climb up… cheers
My normal pressures for trail/enduro riding is 19psi front (2.6 inch wide tyre) and 23psi rear (2.5 inch wide tyre. I weigh 85kg and run innertubes with sealant (I hate fixing tubeless puntures).
I have been running a bit low tire pressure anywhere between 18 psi front 20 psi rear. On the high side for a bit tech I run 21 psi front 23 psi rear. I am also on a Hardtail so I like the lower psi. Great video, you guys rock!
Hailing from Phoenix AZ, USA
Hard Tail: Ragley Big Al 29"
Front: 20psi Rear: 22psi
Full Sus: Rocky Mountain Thunderbolt 27.5"
Front/Rear: 22psi
Been thinking of running 2psi more on both bikes recently.
Would be nice to see a 3rd comparison with the actual tire pressure you plan to run using what you learned in this video.
How about a high or low tire pressure for hardtail? Considering there’s no back suspension to absorb the power from the tire
So many varied opinions on this topic… I was reading a Canyon article a couple of weeks ago that recommended 23/24f & 27/28R as a good starting point, and then a day or two later I read another article that suggested much lower PSIs to start.
I think it comes down to a combination of personal preference, trail conditions and tyre choice. I also think it’s good to experiment with different setups like Neil did in this video, until you find a setup that works for you.
Is there a relationship with tire pressure and interior rim width? I have some CF wheels on my xc bike that are rather narrow - I think 23 mm internal. I weigh 185 lbs (84 kg). If I am below 28 psi in the rear the tire is really squirmy in turns throwing the bike out off balance. Any thought regarding rim width?
My go-to pressure for general trail riding (xc-bike) is 15 psi front and 17 in the rear. If conditions are really wet and muddy a couple of psi lower. And for long distance rides on mainly gravel roads I usually go for 18/20 psi. Lightweight rider 🪶
I run tire inserts front & rear (Rimpacts) along with very low psi, 15/19. This on 29 x 2.5/2.6 on both, my hardtail and my fullsus. I weight about 185 lbs. This setup has never given me a flat tire and rolling fast down chunky rocks is very smooth and predictable. Still feels good in corners.
I have run 15psi front and 18psi rear but I was permanently aware of pinch flats but the terrain I ride needs as much grip as possible in winter. I have since run 30psi rear and 25psi front and the grip level is less but the rolling resistance is also way less which is a positive. I might try 25 rear 20 front and see how it goes.
When I added inserts front and back, I dropped to 18psi up front and 16psi in rear. I have since removed the front insert and increased to 24psi rear and 20psi front. Works for me on techy singletrack.
I've had a couple of those Topeak pressure gauges - they were so inaccurate that they were really random number generators.
I have Topeak shock pump and Topeak pressure gauge, never get the two to agree!
Looking a bit outside of the MTB bubble the whole topic can be read up on in the publications of Jan Heine. -> basically the guy who brought back 650b for drop bar bikes.
I currently run Maxxis DD rear and Exo+ front on my bike with 25R and 24F. During the summer when speeds are up, if I use much lower pressure I can get some rim smacks and see sealant striping on the sidewalls, which I assume is maybe from burping in corners and a little sealant escapes.
Great video 😃 3-2-1 countdown just like a real match 😂😂
Neil riding is so good!
So, yes, we spotted the continuity error in the footage of the timed runs. Out the start hut with a full-face and then footage shows riding with an open face ! On both timed runs....re-using footage multiple times...yes, we spotted the lazy filming 🤣🤣
Psi.. 19 front, 21 rear with xc cushcore inserts. Running schwalbe supertrail. Smooth, fast and stable
2021 NP Mega 29. Kenda Hellkat F&R. 19f 22r for my low 20f 23r for my high pressure.
Hardtail, 27.5x2.6, 195 lb (90 kg), 14 psi front and rear when I'm riding the loose sandy stuff here in Florida, up to 24 psi for hard packed dirt at the local jump trail.
I run 8 upfront and 9 3/4 in rear, wicked good
I run Maxis Minion DHF on front and rear, 27.5s . 18 to 20 in front and two psi higher in rear.
Softer tires will deform inward on impact inward and then flex outward returning most of the energy. Harder tires tend to hit the bump and bounce towards the rear. In other words a softer tire rolls over objects more efficiently.
🔥music as always.
i just asked my frend the same question thx for the video
I have always run lower tire pressure. Even at 195lbs and on a emtb I run my Rocky Mountain Powerplay Altitude A30 coil at 18lb up front and 20lb out back. No cushcore in the back yet but if I ad one I will drop the rear to about 18lb.
crazy...I really would of thought harder tyres would be faster than soft, so i guess surface & tyres compound is something that we should pay more attention to rather than supposing that the settings we choose will do, i have my tyres rock hard most the time but in bad weather then will let them down but does depend on tyre compounds, im gonna try this test myself
I usually run about 24psi in front 27 in rear. Lowest I ever go is 23 front 26 rear
If I rode 18/20 I would rim out on everything. I often rim out if my pressure is under 26.
19 & 17 PSI for usual Surrey Hills rides. I'm 73kg and riding an E-Enduro bike
I'm a big guy, so I'm usually 30 Rear and 28 Front. If it's soft (muddy, snowy, or raining) I'll go 28R and 26F. But, as a big guy; the performance coming back down is not nearly as important as the effort to climb up. When it takes an hour to climb and 10 minutes to come back down you get some wiggle room.
The trails around here are super rocky and chunky like some of the parts that he was riding in the test. I'd love to see what high vs low pressure does for climbing.
Try some conti tyres, their sidewalls are a bit firmer so you can get away with less pressure while maintaining a decent level of support. Their trail tyres are more or less the same stiffness as an exo plus maxxis so an enduro or dh would be firmer still.
I think the theory is the same as for adding more suspension. it reduces the energy losses from the up down deflection of your mass. So the overall efficiency of conversion from potential to kinetic energy is improved. The net speed is higher. On a smooth trail where there are no up down deflections, the increased contact patch drag of a flatter tyre should be dominant and you might expect to see slower net speeds. A tarmac test would be a good test to compare with the fire road test.
Forest trail.....18f 20r.....mixed xc type rides 22f 24r.....rocky terrain 24f 26r.......27.5 or 29 both on emtbs
Tubeless allows lower pressures but I dont like the squirmy feeling of sub 20 psi tires. I run 27-30psi and still using tubes. As long as I keep my tires inflated properly pinch flats arent a big deal for me.
It depends very much on where you ride too. Here in the PNW with cushcore front and rear I ride 23/21 psi
Like the video - but no mention of rider weight and how it impacts the tire pressure for each person? Wondering if 1-2 seconds is really relevant given all the subjective factors of riding...
A lot of people don't know this specially the e bikes but higher tire pressure creates more rolling resistance with fat tire. After a certain point they start to ride bumpier creating more resistance. After fifteen pounds that's it, you're going to create more rolling resistance and have a lot more flat tires.
I’m sure you’re already aware but to help counter that roll effect when running low pressure you could put a tyre insert in. I use inserts and I’ve ridden as low as 4.5psi. It wasn’t intentional to run that low but I had forgotten my pump 🤦♂️ I usually run 20/16. Riding weight with pack 72kg
I'm not surprised about the fire road test. On my fat bike (7PSI front, 6PSI rear), I almost always roll faster than the others.
80kg rider / 15,6 enduro bike on schwalbe Magic Mary front, Hans Dampf rear, both super tail casing, for loamy not too rocky 20f / 23r , rocky hard terrein(tarmac) 23f / 25r, that will be my highest, cheers
Forget rolling resistance. If I go lower than 30 front and 32 rear it gets squishy in the berms and when I pump rollers or jumps the rear will usually burp and send me off trail to the left. I’m not too heavy either @ 185 lbs with gear.
I generally do run lower than your pressures. For 29x2.4 I'm running 22psi rear 20 psi front. I do know if I go lower I will feel the tyre rolling. My tyres have apex protection but tubeless.
Hi Neil, great video 🎉. I've stopped using air altogether. After watching a memory foam advert I found out they used nasa tech. I fill my tyres with
For me 20 psi is the golden standard. Maybe little harder in the back and a little softer in the rear may be optimal like 19/21 or 18/20. But my pump is way to cheap to be that accurate, so aiming for 20 is my go to. I feel like i can push hard on both rocks and in berms without hesitation still.
I run atomik am 35 (carbon) w/cushcore wrapped in Maxxis Assigui 2.6 F/R at 22psi.... I'm 195lbs. on a XL NP Scout. I'm also a slower rider and probably don't hit the rocks as hard as those who are a bit faster than I.
Very enjoyable watch. .....Recently converted to tubeless tyres, but running at my old tubed pressures of 35psi will now be experimenting with lower readings, starting with say 28psi and working down in small increments....thanks Neil for posting.... Ps I'm currently looking at MTB tyre sizing ie width for a 29er when mainly xc/trail type riding. How do the same manufacturers spec tyre perform on the bike in their 2.25' 2.3'' & 2.4" sizes, currently 'scratching my head' trying to decide on widths!
In theory wider tyres means more stability and cornering, while thinner ones means lower weight and rolling resistance, so more speed. Tyre pressure could also need to change between different sizes for you, as a larger one will also give more support
If you're running tubeless and are approx 180 lbs / 82 kg rider, you should look at dropping psi significantly to the low 20's (21f/23r) while using a tire with a decent sidewall (Maxxis EXO+ or firmer, for example). And then if you're running rockier terrain, either up your psi a touch or run a stiffer sidewall. If you're a beefier rider, up the psi a bit. But 35 psi is quite high.
32R 30F at 17.5 Stone, 245lb, 111kg on 2.8" Schwalbe trail casing tyres.
I'm 77kg, run 18-20 up front, 19-21 at the back, with Cush-Cores in both, though.
Keep the low pressure and add an insert that gives sidewall support and you will be sorted.
love the video
I run 19 psi up front with 22psi in the rear and get great results, with that being said im only 60kg
that is on my hardtail btw
I think there's a lot more variables that need to be considered for not just a fast time, but more importantly a safe one. What is the tire width? How much does the rider weigh? What is the manufacturers recommended minimum psi? For me personally, I never go under the manfacturers minimum rec. PSI. For my RaceKing's, which 2.2's, I never go under 40 psi. I ride on the road and sometimes off road (no trails yet), and I'd rather not have my psi lower than that. Other than that I don't worry too much about tire pressure.
Is there a specific reason that you would run that high? Are you a very large rider? If you’re running tubeless, I feel like you should test out some lower pressures. That’s a really high tire pressure to run off road.
Terrain/ conditions. Make a massive difference. In the winter, in the woods, as low as I can go. It's slower and need more grip. The summer, on rocky terrain and berms and jumps - higher. To stop burping and bottom outs. But still 25psi max.
I have raced enduro for years on 15 front 20 rear, no inserts and I've had no issues with 2.6 x 29 Grid Trail casings. I only weigh 130 pounds though.
Hardtail. 27.5, 2.8” plus tires. 15 psi rear, 14 psi front.
I'd do this test on a soft (loamy?) soil surtface to allow the tread to actually angage the surface. Rolling resisance on pavement or gravel is a different animal ....
Lower pressure with dh casing and some kind of insert is key i think
24F 28R 29er 2.25 Vittoria Barzos xc Hardtail
I really think sidewall stiffness matters for low pressure hookup and rider weight is key too (me at 210 and my friend at 250, quite different pressure). I've been running 16psi F 20psi R for years on rough terrain, but thats with a Assegai EXO F and 72tpi rear (or double down) if it was a thin sidewall tire or I was a heavier rider OR and this is key, I was a former pro-downhill racer who rails corners on a level that I am nowhere close too, I'd roll it over and bottem out. I think Pro's (and Ex pro's) run much higher pressure as they put forces on tires us amateurs do not exert, having seen high level riders up close, and knowing that I'm not close to that, this is our rider conclusion. Also as a avid fat biker I'm super fidgity about every single psi difference and always have my gauge with me to make it perfect for conditions and carry this over into summer biking. Next test, pressure AND sidewall comparison, 15psi on DH sidewall Maxgrips vs 15psi on Enduro\trail casing ( effect of tire rubber compound natural rebound properties in action)
Depends what your riding , if your doing long rides on washboard tractor trails and grass hard tyres slow you right dont , like your bikes juddering to a stop. Big hits harder soft allday rides softer,
LW Rider 20 / 20 Ride Vancouver Fast Park Type Riding 24 / 24 😎
I run 19psi up front and 23psi in the rear. Much more comfortable and a lot more grip than higher pressures.
I run 15psi front and rear in my 29" mezcals. I weigh 136lb. Kona HEI HEI 100mm travel both ends.
20 back 18 front is what I use on my hardtail and when I got a full suspension I kept it the same any higher or lower seems to loose performance . Now I use maxxis tires with the exo casing which I think allows softer pressures being a stout casing . I ride in the high desert with rock sand and hard pack.
Now science does say softer is more efficient all around . I think that argument is over .
Consider this like the Pirate code, a Guideline!!😂 Everyone needs to figure it out for their bike, their trails and even more importantly their pressure gauge! Then when you go & ride different trails, figure it out again!
thinking those pressures for trail riding the LOW's would be great, traction for climbing.. but downhill slightly higher. would have liked to hear the tires more and the pacman music less.
I hope those advocating for sub 20 PSI are running tire inserts. 😲
I like to get the pressure as low as possible but still high enough to avoid the tire rolling over / burping in a berm. So 23 - 27 PSI.
With supporting inserts you can even get much lower than that. But I don't use them anymore because they are just a pain to deal with when it's time to replace tires.
the lowest i've been was actually on a tubed tyre.
old irc Kujo 2.35inchx24 on sun double wide 46mm rims back in 2002/3. 17-18psi, was supppper grippy. no pinch flats as the kujo had foamfilled side walls to stop that and the wide rim made them super square
this was on an old rocky mountain rm7, with maz jnr T 170mm forks and 3x9 gears hahahaha
What about effect of tyre pressure in damper, slicker conditions?
What casing are you running? I recently tried the bontrager g5 team issue and I had to go down in pressure compared to maxxis dh casing. The sidewalls are way stiffer and the knobbs are slightly less grippy. I'm running 20 psi in the front and 25 in the rear at 270lbs. I cant run anything other than dh casing even at 50 psi because I will slice the tire. Also I switched to carbon rims (we are one - strife) and I no longer have to worry about rim strikes. I use cush core in the back and currently have no insert in the front. I accidentally rode with 10psi on the front and back and had no problems except for tire squirm in faster berms.
fwiw. I tend to run 25/25psi (tubeless 2.6 width tyres on 27.5 wheels) and call it good... maybe dropping the front to 22psi if I want a little more bite. As you've surmised somewhere between the two extremes you tried (and essentially what you were running previously) seems to be a good compromise for all-round trail-riding conditions.