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People say lower PSI on the tire makes your biking go faster. Is this true?

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People say lower PSI on the tire makes your biking go faster. Is this true?

Old 01-20-20, 09:02 PM
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Cheez
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People say lower PSI on the tire makes your biking go faster. Is this true?

As the topic said I find it hard to believe how lower pressure on the tires make you go faster... they say lower PSI absorbs the bumps better and prevent the tire from slipping thus preventing from loss of power transfer when you go over rough pavement. But beside that, what about the rolling resistance? Doesn't high PSI do better on the rolling resistance? contact between the tire and the road surface? I always thought higher PSI is better for speed. And doesn't skinny 20 or 23mm tire do better than those fatter tires? like the gravel bikes? People on youtube tend to lean on gravel bikes (wider tires than the road bike) and favor lower PSI... but I think they are smoking something. I just find it hard to accept this.

I didn't have a floor pump til just very recently. I thought I was running well over 100 psi on my 23mm (700c) tires using my little hand pump but was not sure what PSI I was at since it doesn't have the pressure gauge. Since I just got my JoeBlow Sport II floor pump I found out that I've been running at approx 70 PSI!! I was way off. So basically I never rode my bike at 100+ or 120 PSI. So I can't tell what riding at say 110 PSI would be like.... will it let me go faster? I want speed. I want to tweak it so I can get best speed possible.

Last edited by Cheez; 01-20-20 at 09:05 PM.
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Old 01-20-20, 09:19 PM
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No. A lower tire pressure won't make your bike faster. Yes. Some bike tires have lower rolling resistance than other tires. If you want to go faster then study what the riders participating in the Olympics or Tour de France are doing with their bikes.
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Old 01-20-20, 09:31 PM
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Gauges on pumps are notoriously inaccurate. Get a good pressure gauge. I found out the hard way that lower pressures make me slower. I started a club ride with about 85 psi in my tires instead of the normal 100. The group dropped me like a stone in a pond. I pulled into the 15 mile turnaround spot just as they were leaving. I pumped up my tires and chased after them. With full pressure, I caught them at about 2 miles out from the stop, dropped THEM like stones, and was about 2 miles ahead of them by the end of the ride (based on the time difference.)

I now put about 110 psi in my tires, and since doing that I've gone from 3 pinch flats per season to none. Not stopping to fix pinch flats also helps my average speed.

Edit: How much pressure is "proper" depends on the payload the tires are supporting. If you weighed 135 pounds, then 70 or 80 psi might yield the 'ideal' 10-20% deformation whereas I'd flatten a 70 psi tire.

Last edited by BlazingPedals; 01-20-20 at 09:38 PM.
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Old 01-20-20, 09:47 PM
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Originally Posted by BlazingPedals View Post
I started a club ride with about 85 psi in my tires instead of the normal 100. The group dropped me like a stone in a pond. I pulled into the 15 mile turnaround spot just as they were leaving. I pumped up my tires and chased after them. With full pressure, I caught them at about 2 miles out from the stop, dropped THEM like stones, and was about 2 miles ahead of them by the end of the ride (based on the time difference.)
So some quick maths. Let's be conservative and say that the leading group was moving at a modest 15mph pace. Let's assume you needed 2 minutes to air up and set out. To catch them in the span of two miles, which would take them 8 minutes, you would need to cover the same distance in 6 minutes, which is 20mph. Not excessive. Now you must have then slowed down immensely, because your lead after the subsequent 13 miles was only around 2 minutes-- less than 11 seconds per mile. So if they had maintained the same pace, you were going about 3-4% faster.

I've ridden about 30 miles with a 700x23 front with 40psi in it. It was costing me less than 1mph average speed. Cornering was... hairy. The idea that running a tire at a 15% lower pressure would result in a dramatic loss of speed is... questionable at best. Unless of course the roads were basketball court smooth.
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Old 01-20-20, 09:53 PM
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Originally Posted by ramzilla View Post
If you want to go faster then study what the riders participating in the Olympics or Tour de France are doing with their bikes.
Which of course is running the lowest possible tire pressure.
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Old 01-20-20, 10:14 PM
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Originally Posted by BlazingPedals View Post
Gauges on pumps are notoriously inaccurate. Get a good pressure gauge. I found out the hard way that lower pressures make me slower. I started a club ride with about 85 psi in my tires instead of the normal 100. The group dropped me like a stone in a pond. I pulled into the 15 mile turnaround spot just as they were leaving. I pumped up my tires and chased after them. With full pressure, I caught them at about 2 miles out from the stop, dropped THEM like stones, and was about 2 miles ahead of them by the end of the ride (based on the time difference.)

I now put about 110 psi in my tires, and since doing that I've gone from 3 pinch flats per season to none. Not stopping to fix pinch flats also helps my average speed.

Edit: How much pressure is "proper" depends on the payload the tires are supporting. If you weighed 135 pounds, then 70 or 80 psi might yield the 'ideal' 10-20% deformation whereas I'd flatten a 70 psi tire.

So when you were dropped like a stone, that would be going at least 2 mph slower than the group,

and after adding 15 psi, you picked up that speed plus another ~5 mph?

Man, I'm going to put 130 psi in my tires, and hang with the big boys- I'm only about 5 mph slower than them!
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Old 01-20-20, 10:31 PM
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There are trade-offs based on tire and weight. Just cause a tire says 130psi max doesn't mean its faster at that pressure, it will be based to some extent on your weight. At 130lb I pump my wife's tires to 80-85psi, when she races to 90psi which does help for a little extra speed. Going to 130 for her would probably result in a really rough ride, worse I suspect the tire would be more prone to bouncing over rough pavement meaning less control on corners. So maybe an out and back 15-20mi time trial 130 would be ok but a road race course it would be slower and more hazardous. At 275lb I keep my tires at about 95-100psi and bump to about 115psi, over that it does get bumpy for me as well and again has a negative impact on how I'll corner and how I feel after more then an hour.
Gravel bike has wider tires that can handle 85psi and I keep them at 65, after 5hrs in the saddle I feel fine, no aches or stiffness. Lower pressure is faster for being able to just keep going at a steady output. Play around with pressure and figure it out for yourself what feels best, handles well and seems to go quickest.
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Old 01-20-20, 10:38 PM
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Cheez
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Originally Posted by BlazingPedals View Post
Gauges on pumps are notoriously inaccurate. Get a good pressure gauge. I found out the hard way that lower pressures make me slower. I started a club ride with about 85 psi in my tires instead of the normal 100. The group dropped me like a stone in a pond. I pulled into the 15 mile turnaround spot just as they were leaving. I pumped up my tires and chased after them. With full pressure, I caught them at about 2 miles out from the stop, dropped THEM like stones, and was about 2 miles ahead of them by the end of the ride (based on the time difference.)

I now put about 110 psi in my tires, and since doing that I've gone from 3 pinch flats per season to none. Not stopping to fix pinch flats also helps my average speed.

Edit: How much pressure is "proper" depends on the payload the tires are supporting. If you weighed 135 pounds, then 70 or 80 psi might yield the 'ideal' 10-20% deformation whereas I'd flatten a 70 psi tire.
LOL thanks.. Good to know that higher PSI yield to better rolling speed. Man then I would be flying at 110 PSI since I'm used to 70 PSI. I need to try this soon for myself.

Originally Posted by woodcraft View Post
So when you were dropped like a stone, that would be going at least 2 mph slower than the group,

and after adding 15 psi, you picked up that speed plus another ~5 mph?

Man, I'm going to put 130 psi in my tires, and hang with the big boys- I'm only about 5 mph slower than them!
I think there is mental strength come into play depending on the PSI also. If the tire rolls easier (due to higher PSI) you gonna feel better as you ride it. It would increase morale. You will want to go faster and faster so as a result you can drop somebody like a stone. Both physics and mental health count.

Last edited by Cheez; 01-20-20 at 10:42 PM.
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Old 01-20-20, 10:38 PM
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This whole idea that wider tires run at lower pressures comes from Jan Heine (Rene Herse Cycles, formerly Compass Cycles, Bicycle Quarterly, etc.) and research he carried out. It can be controversial, and people love to have an opinion on Jan Heine, his testing methodology, and his assertions. I would recommend reading what he has to say and carefully examining his test results and methodology before coming down on one side or another.

Basically, what he's saying is that with very supple tire casings, making for light and extremely flexible tires, tires wider than traditional road tires (think 650x42B vs 700x23C) run at lower pressures can be as fast or faster than traditional road tires. By absorbing small bumps in the road, and imperfections in paved surfaces, supple, wider tires at lower pressures can be faster than narrow tires at higher pressures.

I may not have explained it satisfactorily, but there is a wealth of information out there that you can access to bring yourself up to speed. The following articles and blog posts are all by Heine himself, but a little Googling should find some other articles.

https://www.roadbikerider.com/the-ti...-jan-heine-d1/

https://www.renehersecycles.com/test...res-isnt-easy/

https://www.renehersecycles.com/myth...ure-is-faster/

Last edited by PDKL45; 01-20-20 at 10:42 PM.
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Old 01-20-20, 11:42 PM
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its all about the surface you are riding on and the suppleness of your tire. Like the above poster said.

if you are riding on rougher surface, then yes a lower tire pressure can be more efficient and less jarring on the body

if you are riding on a very smooth surface then a relatively higher tire pressure will be more efficient, look at a track rider in a velodrome.

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Old 01-20-20, 11:57 PM
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on the velodrome, you pump the tire up to the highest psi possible! What's the point of using stiff frame, crank, wheels, only to have squishy tires???

on the a typical A grade road, if using 25mm tire, and you're 150 lbs, pump tires to 95 psi front, 100 rear.. mininum!
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Old 01-21-20, 01:20 AM
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Yeah the type of road makes a pretty big difference as well. Asphalt vs Concrete.. Asphalt is soft and it makes you feel like you are on very low tire pressure. On concrete it's a 180 degree difference.
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Old 01-21-20, 01:46 AM
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I did a ride up a local mountain road not long ago. I had somehow picked up a thorn in my front tire on the 8 mile climb. The air pressure when I got to the top was about 60 psi.

On the way up, I did not realize it, didn't feel any signs of bouncing etc. But it sure was tough and when I got to the top, I thought I was going to puke!

Fuuuuuuuudge on those low tire pressures, didn't make me any faster on the climb!
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Old 01-21-20, 03:52 AM
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Here's another comparison to throw into the mix: Bicycle Rolling Resistance

Of course, he's only testing under one very specific set of circumstances but it's still quite compelling. Sadly I don't think my bike will take anything over 25mm.
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Old 01-21-20, 05:14 AM
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For every kind of (real world) surface, tire and bike+rider weight there is a sweet spot for tire pressure. Going higher makes the tire bounce on every small irregularity and thus slow you down, going lower adds too much rolling resistance due the tire deflection. There is no single perfect pressure for all situations, but there is one for each.
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Old 01-21-20, 05:51 AM
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It is easy to overthink this. Generally, narrower tires are run at higher pressures, but the tire pressure choice is based upon combined rider and bike weight. There are some simple charts on the internet sites for some of the tire manufacturers that may help you get in the ballpark (Michelin used to have one when Imwas looking). Just be sure you are using enough pressure to prevent rim strikes and pinch flats---beyond that, the world is your oyster.
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Old 01-21-20, 07:09 AM
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Originally Posted by PDKL45 View Post
This whole idea that wider tires run at lower pressures comes from Jan Heine (Rene Herse Cycles, formerly Compass Cycles, Bicycle Quarterly, etc.) and research he carried out. It can be controversial, and people love to have an opinion on Jan Heine, his testing methodology, and his assertions. I would recommend reading what he has to say and carefully examining his test results and methodology before coming down on one side or another.

Basically, what he's saying is that with very supple tire casings, making for light and extremely flexible tires, tires wider than traditional road tires (think 650x42B vs 700x23C) run at lower pressures can be as fast or faster than traditional road tires. By absorbing small bumps in the road, and imperfections in paved surfaces, supple, wider tires at lower pressures can be faster than narrow tires at higher pressures.

I may not have explained it satisfactorily, but there is a wealth of information out there that you can access to bring yourself up to speed. The following articles and blog posts are all by Heine himself, but a little Googling should find some other articles.

https://www.roadbikerider.com/the-ti...-jan-heine-d1/

https://www.renehersecycles.com/test...res-isnt-easy/

https://www.renehersecycles.com/myth...ure-is-faster/
Yes, the wider tires run at lower psi will be faster, all other things equal. But the wider tires are also significantly heavier, too, which is slower.
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Old 01-21-20, 08:11 AM
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If you isolate only one variable and think only about it, you'll always be wrong part of the time.

Assuming everything else is equal, here's two factors that have to do with air pressure:

A major component of rolling resistance has to do with tire suppleness. All pneumatic tires will have a flat patch on the bottom. The bigger that constantly moving flat patch, the more energy they consume as the tire rotates. On a bicycle that energy ultimately has to come from the rider. So the smaller the flat patch, the faster the tire.
Unfortunately, the roads that we ride on aren't perfect. Even smooth roads have lots of little bumps. When a rock hard tire hits a bump is bounces upward. Where does the energy come from to lift the bike and rider? On a bicycle it ultimately has to come from the rider. A rock hard tire will bump upward more often, consume more energy and be slower.

It's not a perfect example but I became aware of how much time a bicycle tire is off the surface during my early mountain biking days. My first mountain bike had a rigid fork and I used to ride with the same group of guys every Saturday. I was able to keep up with one particular fellow on the downhills, but only with difficulty. The Saturday after buying an aftermarket suspension fork with rudamentary damping, I discovered that not only was it easy to keep up with him, but when the opportunity presented itself, I could pass him with ease on the downhill. The only difference was the damped suspension that let me keep my front wheel on the ground better.
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Old 01-21-20, 08:11 AM
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Originally Posted by Koyote View Post
Yes, the wider tires run at lower psi will be faster, all other things equal. But the wider tires are also significantly heavier, too, which is slower.
First, just because one effect is to make the bike faster and another makes it slower doesn't mean the net is zero. You have to compare the magnitudes of the effects and in this case the benefit of lower rolling resistance greatly exceeds the cost of the lower weight. Second, I don't know your definition of significant, but in the context of the total bike/rider system, I'd say the difference in weight between tires of similar quality, but different sizes is negligible. I see for a pair of Vitttoria Corsa G+ tires the difference is 50 g. for a bike/rider weight of 68 kg (a light 150 lb), that amounts to 0.07%.
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Old 01-21-20, 08:12 AM
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It might--here's an article which I found interesting: https://www.roadbikerider.com/the-ti...-jan-heine-d1/
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Old 01-21-20, 08:15 AM
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Originally Posted by Retro Grouch View Post
All pneumatic tires will have a flat patch on the bottom. The bigger that constantly moving flat patch, the more energy they consume as the tire rotates. On a bicycle that energy ultimately has to come from the rider.
What about the energy returned when the tire decompresses? Rolling resistance is a function of the difference between the energy required to deform the tire and the energy returned when it relaxes multiplied by a geometric term related to the length (not area) of the contact patch which increases monotonically with length.
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Old 01-21-20, 08:18 AM
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Originally Posted by asgelle View Post
First, just because one effect is to make the bike faster and another makes it slower doesn't mean the net is zero. You have to compare the magnitudes of the effects and in this case the benefit of lower rolling resistance greatly exceeds the cost of the lower weight. Second, I don't know your definition of significant, but in the context of the total bike/rider system, I'd say the difference in weight between tires of similar quality, but different sizes is negligible. I see for a pair of Vitttoria Corsa G+ tires the difference is 50 g. for a bike/rider weight of 68 kg (a light 150 lb), that amounts to 0.07%.
Please read my post. I never stated (nor implied) that the net effect is zero. I was merely pointing out that there is a tradeoff.
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Old 01-21-20, 08:22 AM
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Yes, true: if and only if your current pressure is high enough the tires either cannot roll over the terrain the are designed for.

The optimal pressure and tire size for a perfectly new road is different than the pressure and size for gravel riding is different than racing cyclocross etc................

Like this:
Time trial on a brand new smooth road: 23mm/25mm combo at 90psi
Road riding some chipseal with lots of cracks/bumps/imperfections: 25's or 28's at 65-80psi
Gravel grinding: 32-40mm tires in the range of 25-40psi
Cyclocross racing: 32mm tubular down to even 15psi

Optimization based on environment. You can do roll down tests.

Now, I do see roadies running 28's at such low pressure it looks like the tire is going flat during the group rides. And that's where they like it. But, that's slow.

Plenty of stuff online about this topic, some might take more research than others to find.
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Old 01-21-20, 09:01 AM
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Mission accomplished!
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Old 01-21-20, 09:58 AM
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Originally Posted by PDKL45 View Post
This whole idea that wider tires run at lower pressures comes from Jan Heine (Rene Herse Cycles, formerly Compass Cycles, Bicycle Quarterly, etc.) and research he carried out. It can be controversial, and people love to have an opinion on Jan Heine, his testing methodology, and his assertions. I would recommend reading what he has to say and carefully examining his test results and methodology before coming down on one side or another.

Basically, what he's saying is that with very supple tire casings, making for light and extremely flexible tires, tires wider than traditional road tires (think 650x42B vs 700x23C) run at lower pressures can be as fast or faster than traditional road tires. By absorbing small bumps in the road, and imperfections in paved surfaces, supple, wider tires at lower pressures can be faster than narrow tires at higher pressures.
In the last few years, Heine has been pushing his own tires, which may be a bit faster, but they're among the most expensive tires I know of (for the sizes he sells). The trade-off for the most supple ( = faster at lower pressures) tires is that they're $75 apiece, and because they're thin, you can expect them to have a shorter life than tires with a bit more tread, and the more expensive tires may be more susceptible to flatting than the heavier, cheaper tires.

My trade space has a hard time spending a year's tire budget on two tires that'll likely wear out in 3-4 months. But I don't race; if you do, or if you've got a big ride planned where an extra mph will make a difference in your enjoyment, you may decide otherwise. I guess that's what "YMMV" means.
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