Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

Tire pressure vs Speed Question

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

Tire pressure vs Speed Question

Old 12-04-21, 08:24 PM
  #1  
AJW2W11E
Senior Member
Thread Starter
 
Join Date: Sep 2021
Posts: 153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 104 Post(s)
Liked 26 Times in 20 Posts
Tire pressure vs Speed Question

I've been riding for two years. I have a Giant Toughroad, which is not a fast bike. I am not that fast either.
My tire pressure was getting low and today I put some air in. Before, you could squeeze them and they were hard as maybe a beachball, 60 psi, but today I had them slightly less than rock hard, maybe 80 psi.
When I went out, it was raining like hell and windy and cold and starting to freeze . My feet were soaked then feeling funny and I got concerned so I jacked up my speedto get home fast.
With the higher pressure, I noticed I was moving pretty briskly and then I noticed was able to use the big ring and smallest cog the whole 30 miles and cut 20 minutes of my time.
That being said, what 32 to 35 mm inner tube can be pumped up to 100 psi like a road bike?
Next, at what psi does this effect wear off. I'm guessing 120 is the limit? Because after that, rock hard is rock hard?
Sure had some fun today...or was it my imagination? BTW my lower legs and feet were purple and my hands were too.

Last edited by AJW2W11E; 12-04-21 at 08:27 PM.
AJW2W11E is offline  
Old 12-04-21, 08:31 PM
  #2  
vespasianus
Senior Member
 
Join Date: Jul 2019
Location: In the south but from North
Posts: 477

Bikes: Turner 5-Spot Burner converted; IBIS Ripley, Specialized Crave, Tommasini Sintesi, Cinelli Superstar, Tommasini X-Fire Gravel

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 257 Post(s)
Liked 237 Times in 131 Posts
Originally Posted by AJW2W11E View Post
I've been riding for two years. I have a Giant Toughroad, which is not a fast bike. I am not that fast either.
My tire pressure was getting low and today I put some air in. Before, you could squeeze them and they were hard as maybe a beachball, 60 psi, but today I had them slightly less than rock hard, maybe 80 psi.
When I went out, it was raining like hell and windy and cold and starting to freeze . My feet were soaked then feeling funny and I got concerned so I jacked up my speedto get home fast.
With the higher pressure, I noticed I was moving pretty briskly and then I noticed was able to use the big ring and smallest cog the whole 30 miles and cut 20 minutes of my time.
That being said, what 32 to 35 mm inner tube can be pumped up to 100 psi like a road bike?
Next, at what psi does this effect wear off. I'm guessing 120 is the limit? Because after that, rock hard is rock hard?
Sure had some fun today...or was it my imagination? BTW my lower legs and feet were purple and my hands were too.
With all this talk about softer tire pressures, in circumstances where the roads are good, narrow tires with high pressures are really fast. But I don't think there are many 35mm tires that can be pumped to 100psi.
vespasianus is offline  
Likes For vespasianus:
Old 12-04-21, 09:00 PM
  #3  
cxwrench
Senior Member
 
cxwrench's Avatar
 
Join Date: Jul 2013
Location: Nor-Cal
Posts: 2,876

Bikes: lots

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1410 Post(s)
Liked 1,972 Times in 1,047 Posts
Physics being what it is you definitely don't want to pump a 35mm tire up to 100psi. That would be the rough equivalent of a 23mm tire at 140psi. It doesn't matter which inner tube you use, it will only expand as big as the tire...so you could theoretically inflate any tube to 200psi if the tire would stay on the rim. Guessing about your ideal pressure is useless unless we know how much you and your bike weigh AND what the road surface you ride on is like.
cxwrench is offline  
Old 12-04-21, 09:38 PM
  #4  
billridesbikes
Senior Member
 
Join Date: Nov 2019
Posts: 668
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 324 Post(s)
Liked 393 Times in 236 Posts
I got my wife some Vittoria Zaffiro pros 32s for the winter, which say they can be pumped up to a maximum of 100psi. Although normally I have hers at about 60/65psi for fall riding. Interestingly, as a side note, the Vittoria's measure 29.5mm on her bike, slightly less then the Continental GP4000iis 28s on my bike that measure 29.8mm.

I'm guessing you probably have tires with stiff casings on your bike like a puncture proof tire or similar? So increasing the tire pressure on them does make some sense, in theory some better tires will maybe run with lower rolling resistance at lower inflation than your tires.

https://www.roadbikerider.com/the-ti...-jan-heine-d1/
billridesbikes is offline  
Old 12-04-21, 10:09 PM
  #5  
Russ Roth
Senior Member
 
Join Date: Dec 2019
Location: South Shore of Long Island
Posts: 2,078

Bikes: 2010 Carrera Volans, 2015 C-Dale Trail 2sl, 2017 Raleigh Rush Hour, 2017 Blue Proseccio, 1992 Giant Perigee, 80s Gitane Rallye Tandem

Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 785 Post(s)
Liked 629 Times in 477 Posts
In the same road tire, higher pressure will run faster since the higher pressure will reduce the contact patch. But as roads aren't usually smooth, past a certain pressure the resulting road vibration can create greater fatigue slowing you down and make the bike less stable/more bouncy over rough patches requiring slower speeds. Optimal pressure is based on your weight, tire size, materials, rim size, and road conditions. Strictly road I don't have any tire under 35mm I run at under 80psi for myself or under 70psi for my wife.
Russ Roth is offline  
Old 12-04-21, 10:32 PM
  #6  
AJW2W11E
Senior Member
Thread Starter
 
Join Date: Sep 2021
Posts: 153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 104 Post(s)
Liked 26 Times in 20 Posts
I guess my fast ride today was half due to the 20 extra psi and half due to my imagination . Because its only 8 30 pm here and I need a monster nap.
But do you think those super heavy duty Schwalbe inner tubes could take 75 psi?

Last edited by AJW2W11E; 12-04-21 at 10:36 PM.
AJW2W11E is offline  
Old 12-04-21, 10:47 PM
  #7  
HTupolev
Senior Member
 
Join Date: Apr 2015
Location: Seattle
Posts: 4,035
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 1850 Post(s)
Liked 1,113 Times in 532 Posts
Originally Posted by AJW2W11E View Post
But do you think those super heavy duty Schwalbe inner tubes could take 75 psi?
Any tube can "take" any riding pressure, as long as the pressure doesn't cause the tire to blow off the rim.
HTupolev is offline  
Likes For HTupolev:
Old 12-05-21, 03:31 AM
  #8  
cjenrick
Senior Member
 
Join Date: May 2020
Posts: 409
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 177 Post(s)
Liked 127 Times in 94 Posts
97 psi for everything. rain or shine. rim cuts will slow you down more than your lowered tire pressure will speed you up on bumpy roads.

note that in winter, your indoor bike will lose pressure if you go from 72 degrees to 38 F.

note that if you climb to 5000 feet that your tires will feel like teak wood from less atmospheric pressure.

note that if you brake constantly coming down the 5000 ft peak that your rims will heat up and your handling will feel weird due to hi pressure.

note that if you use wood rims, you will be the coolest cyclist on the block.

Last edited by cjenrick; 12-05-21 at 03:35 AM.
cjenrick is offline  
Likes For cjenrick:
Old 12-05-21, 04:20 AM
  #9  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,919
Mentioned: 31 Post(s)
Tagged: 0 Thread(s)
Quoted: 585 Post(s)
Liked 570 Times in 228 Posts
Originally Posted by Russ Roth View Post
In the same road tire, higher pressure will run faster since the higher pressure will reduce the contact patch.
Size of contact patch doesn't actually have much to do with rolling resistance. Rolling resistance depends much more on frictional losses in other parts of the tire/tube system. It's sort of sleight-of-hand misdirection -- people looked at the tire and thought the losses were related to the contact patch, which they could see since it touches the road; however, most of the losses occur in the parts of the tire that they weren't looking at. That's why latex tubes reduce rolling resistance compared to butyl tubes, even though they don't affect contact patch; and why two tires with the same width and same contact patch but different sidewalls or rubber thicknesses can have different rolling resistance. It's also why knobbed tires can have higher rolling resistance than smooth tires even though their contact patch is smaller.

When you understand that it's not the contact patch per se that matters, it frees you up to look at other components of the system and why lower tire pressure can, in some but not all cases, reduce rolling resistance even though it can increase contact patch. That is, in the same tire, higher pressure will not always run faster.
RChung is offline  
Old 12-05-21, 04:54 AM
  #10  
GhostRider62
Senior Member
 
Join Date: Apr 2021
Posts: 2,207
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 1303 Post(s)
Liked 1,120 Times in 684 Posts
This article explains why rock hard tires usually are not faster. The takeaway is rolling resistance decreases as tire pressure increases until a limit is reached where rolling resistance increases very, very quickly. This inflection depends on the road surface and tire construction.

https://www.velonews.com/gear/road-g...en-testing-it/
GhostRider62 is offline  
Likes For GhostRider62:
Old 12-05-21, 08:10 AM
  #11  
JayKay3000
Senior Member
 
JayKay3000's Avatar
 
Join Date: Mar 2012
Posts: 226
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 46 Post(s)
Liked 78 Times in 50 Posts
Most tires state their theoretical or rcommended limit. I wouldnt exceed what it says on the sidewall.
JayKay3000 is offline  
Likes For JayKay3000:
Old 12-05-21, 08:44 AM
  #12  
Mark Dominck
Senior Member
 
Join Date: Dec 2016
Location: western oregon
Posts: 86

Bikes: Gino Liotto,Kuoto Kharma, Vitus 979, lemond,specialized Tarmac, Austro Daimler Pacifica

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Liked 34 Times in 22 Posts
Originally Posted by billridesbikes View Post
I got my wife some Vittoria Zaffiro pros 32s for the winter, which say they can be pumped up to a maximum of 100psi. Although normally I have hers at about 60/65psi for fall riding. Interestingly, as a side note, the Vittoria's measure 29.5mm on her bike, slightly less then the Continental GP4000iis 28s on my bike that measure 29.8mm.

I'm guessing you probably have tires with stiff casings on your bike like a puncture proof tire or similar? So increasing the tire pressure on them does make some sense, in theory some better tires will maybe run with lower rolling resistance at lower inflation than your tires.

https://www.roadbikerider.com/the-ti...-jan-heine-d1/
very interesting article, so my tubulars pumped up to 120 are are all a fantasy in my mind that I'm going much faster oh well I guess I'm just living in lala land haha
Mark Dominck is offline  
Likes For Mark Dominck:
Old 12-05-21, 09:39 AM
  #13  
GhostRider62
Senior Member
 
Join Date: Apr 2021
Posts: 2,207
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 1303 Post(s)
Liked 1,120 Times in 684 Posts
Originally Posted by Mark Dominck View Post
very interesting article, so my tubulars pumped up to 120 are are all a fantasy in my mind that I'm going much faster oh well I guess I'm just living in lala land haha
Don't feel bad, I used to crank mine to 150 back in the day.
GhostRider62 is offline  
Old 12-05-21, 10:02 AM
  #14  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,919
Mentioned: 31 Post(s)
Tagged: 0 Thread(s)
Quoted: 585 Post(s)
Liked 570 Times in 228 Posts
Originally Posted by GhostRider62 View Post
This article explains why rock hard tires usually are not faster. The takeaway is rolling resistance decreases as tire pressure increases until a limit is reached where rolling resistance increases very, very quickly. This inflection depends on the road surface and tire construction.

https://www.velonews.com/gear/road-g...en-testing-it/
That Zinn article isn't bad. Here's a link to Tom's original discussion of impedance (note how he "undertook an experiment 'on the road' armed with a PowerTap power meter and a method for determining the Crr").
RChung is offline  
Likes For RChung:
Old 12-05-21, 10:21 AM
  #15  
Moles
Junior Member
 
Join Date: Sep 2020
Posts: 22
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked 8 Times in 6 Posts
Here's another...

I watched this well over a year ago, so I can't comment on specific content, but I recall this being a really good in-depth discussion on finding the right tire pressure. Ignore the clickbait-y title...
Moles is offline  
Likes For Moles:
Old 12-05-21, 10:56 AM
  #16  
Pratt
Senior Member
 
Join Date: Aug 2019
Posts: 659
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 244 Post(s)
Liked 242 Times in 157 Posts
You can find out for your tires on your bike by brushing with a friend, thusly:
Start out together, coasting down a hill at the same speed, note who gains.
Now change something on your bike, more pressure, less pressure, what ever, and repeat. Keep everything else the same, same hill, same speed, same position, no changes to friend's bike. Now, did you get faster of slower? Your friend, with unchanged position and bike is presumably the same.
This evaluates the bike, not the terrain, your fitness, the phase of the moon, or any thing else, but it does a good job of that
Pratt is offline  
Likes For Pratt:
Old 12-05-21, 11:39 AM
  #17  
LarrySellerz
Senior Member
 
Join Date: Mar 2021
Posts: 813
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 994 Post(s)
Liked 183 Times in 142 Posts
The recent articles/studies saying that wider tires at lower pressures are just as fast as thin tires at high pressure is Big Gravel trying to n+1 roadies. Follow the money.

OP I'm 250 lbs and run my 33 mm tires at 100+ psi. They say 65 psi on them but they dont break.
LarrySellerz is offline  
Old 12-05-21, 11:50 AM
  #18  
SpedFast
Just Pedaling
 
SpedFast's Avatar
 
Join Date: Oct 2021
Location: West Coast
Posts: 295
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 90 Post(s)
Liked 131 Times in 91 Posts
Originally Posted by AJW2W11E View Post
When I went out, it was raining like hell and windy and cold and starting to freeze
Tailwind!
SpedFast is offline  
Likes For SpedFast:
Old 12-05-21, 12:10 PM
  #19  
Iride01
MotuekaCascadeChinook
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 10,374

Bikes: '20 Tarmac Disc Comp '78 Raleigh Competition GS

Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 4187 Post(s)
Liked 2,709 Times in 1,888 Posts
If you don't have data from multiple rides of the same route, then I'd say all you have is conjecture which is borderline on imagination.
Iride01 is offline  
Old 12-05-21, 01:37 PM
  #20  
WhyFi
Senior Member
 
WhyFi's Avatar
 
Join Date: Jan 2010
Location: TC, MN
Posts: 37,908

Bikes: R3 Disc, Haanjo

Mentioned: 352 Post(s)
Tagged: 1 Thread(s)
Quoted: 19421 Post(s)
Liked 7,991 Times in 4,029 Posts
Originally Posted by RChung View Post
That Zinn article isn't bad. Here's a link to Tom's original discussion of impedance (note how he "undertook an experiment 'on the road' armed with a PowerTap power meter and a method for determining the Crr").
What was that - the good ol' Chang Method?







WhyFi is offline  
Likes For WhyFi:
Old 12-05-21, 04:05 PM
  #21  
cxwrench
Senior Member
 
cxwrench's Avatar
 
Join Date: Jul 2013
Location: Nor-Cal
Posts: 2,876

Bikes: lots

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 1410 Post(s)
Liked 1,972 Times in 1,047 Posts
Originally Posted by LarrySellerz View Post
The recent articles/studies saying that wider tires at lower pressures are just as fast as thin tires at high pressure is Big Gravel trying to n+1 roadies. Follow the money.

OP I'm 250 lbs and run my 33 mm tires at 100+ psi. They say 65 psi on them but they dont break.
Stop it Larry.
cxwrench is offline  
Likes For cxwrench:
Old 12-05-21, 04:25 PM
  #22  
rumrunn6
Senior Member
 
rumrunn6's Avatar
 
Join Date: Jul 2008
Location: 25 miles northwest of Boston
Posts: 27,218

Bikes: Bottecchia Sprint, GT Timberline 29r, Trek FX Alpha 7.0

Mentioned: 106 Post(s)
Tagged: 0 Thread(s)
Quoted: 4503 Post(s)
Liked 2,110 Times in 1,442 Posts
I suspect that's best you'll get out of those tires on that bike. but keep experimenting & report back. maybe w/ a pic next time
rumrunn6 is offline  
Old 12-05-21, 05:32 PM
  #23  
AJW2W11E
Senior Member
Thread Starter
 
Join Date: Sep 2021
Posts: 153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 104 Post(s)
Liked 26 Times in 20 Posts
Originally Posted by SpedFast View Post
Tailwind!
tailwind plus the desire to get home fast. I was soaked.
My legs and feet and hands were dark red / purple. I prepared a hot bath, but I couldnít even feel the temperature so I didnít get in, was afraid I might burn or scald myself.
My first priority is not hi pressure tires. Itís rain pants rain shoes and waterproof gloves. Rain is worse than snow.
AJW2W11E is offline  
Old 12-06-21, 12:42 AM
  #24  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,919
Mentioned: 31 Post(s)
Tagged: 0 Thread(s)
Quoted: 585 Post(s)
Liked 570 Times in 228 Posts
Originally Posted by WhyFi View Post
What was that - the good ol' Chang Method?

The relevant piece is that he discovered it by doing field tests on the road, not in the lab. Until then, doing high-precision road tests was a huge PITA so no one did them (it's still kind of a PITA, just less than before). Actually, when he told me about the planned experiment I wasn't sure he'd be able to get the necessary precision and resolution, so when he said that he had some puzzling results my first thought was "I told you so" and that the finding was garbage. But we looked at his data, and we tried to figure out what he'd done wrong, and he re-ran some tests, and we re-analyzed the data. And the results replicated. I was agog. I think the two lessons are: 1) Tom is a really good experimentalist, much better than I am, damn him; and 2) when he found an unexpected result, he tried to figure out what he'd done wrong and to reject it. He didn't start with a hypothesis and then do experiments to prove it; he had data that showed something unexpected and odd and tried to figure out what went wrong. In the end, we have to go with the data, and in this case it forced us to change our minds and learn something we hadn't previously known. That's always cool.
RChung is offline  
Likes For RChung:
Old 12-06-21, 05:30 AM
  #25  
rumrunn6
Senior Member
 
rumrunn6's Avatar
 
Join Date: Jul 2008
Location: 25 miles northwest of Boston
Posts: 27,218

Bikes: Bottecchia Sprint, GT Timberline 29r, Trek FX Alpha 7.0

Mentioned: 106 Post(s)
Tagged: 0 Thread(s)
Quoted: 4503 Post(s)
Liked 2,110 Times in 1,442 Posts
Originally Posted by AJW2W11E View Post
tailwind plus the desire to get home fast. I was soaked.
My legs and feet and hands were dark red / purple. I prepared a hot bath, but I couldnít even feel the temperature so I didnít get in, was afraid I might burn or scald myself.My first priority is not hi pressure tires. Itís rain pants rain shoes and waterproof gloves. Rain is worse than snow.
barmitts are good for rain too, not just cold
rumrunn6 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.