Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

Tire Pressure - The harder the better?

Notices
Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Tire Pressure - The harder the better?

Old 04-13-11, 01:12 PM
  #26  
motobecane69
Banned.
 
Join Date: Mar 2011
Posts: 1,095
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by FasterNearGirls View Post
Will the highest pressure possible give me the least rolling resistance and more speed however a rougher ride and less grip? That's what I always thought but I read somewhere that a harder tire is actually slower. (?)

On my 25C maximum recommended 130 psi, i usually inflate it to just over that; about 135 psi (I'm 163 lbs).

Same with my 23C Pro Race max = 116 and I go slightly over.

Thanks!
I ride 25's and I'm 80lbs lighter than you and run slightly lower pressures than what you are running. you are doing yourself a disservice in the ride quality dept. When I ride my commuter with 35c tires I love it because they can actually be run at pressures that don't give a bone jarring ride all the time. The fact is that at 245lbs, many tires aren't spec'd for the proper amount of pressure I need in order to get the so called 15% desireable tire drop to maximize comfort and rolling resistance.
motobecane69 is offline  
Old 04-13-11, 05:29 PM
  #27  
vision646
Senior Member
 
vision646's Avatar
 
Join Date: Dec 2010
Location: Tucson, AZ
Posts: 241

Bikes: Campania Challenger

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by tuxbailey View Post
Check PSIMET's tip of the day from way back then.
I used his formula but it tells me that I should be riding at 91PSI, my tires are 90max. How do I adjust? 90/120*Psimet's equation? that would give me 68 PSI.....
vision646 is offline  
Old 04-13-11, 05:33 PM
  #28  
wrr1020
Senior Member
 
Join Date: Mar 2010
Location: So Cal
Posts: 1,153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I should lower my tires, i'm only 145 pounds and usually pump both front and rear to about 110-115.
wrr1020 is offline  
Old 04-13-11, 09:25 PM
  #29  
MAK
Member
 
Join Date: Jun 2005
Location: Delaware
Posts: 1,377

Bikes: Yes, I have bikes.

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 142 Post(s)
Likes: 0
Liked 12 Times in 5 Posts
Another variable???

I ride Conti 4000s 23c tires and always pump to 120-123 psi both front and back. I'm 225 lbs and pump them up to the tires recommended max to avoid pinch flats. So far after thousands of miles I haven't had one pinch flat. (I probably just jinxed myself but oh-well.)

Is there a formula that applies the riders weight to tire pressure that provides a suggested minimum psi that will protect against pinch flats? I'm not racing so a mph or two doesn't make a big difference to me.

Thanks for any input.
MAK is offline  
Old 04-14-11, 04:46 AM
  #30  
datlas 
Beyond Bogus
 
datlas's Avatar
 
Join Date: Dec 2007
Location: Malvern, PA (20 miles West of Philly)
Posts: 28,761

Bikes: 1986 Alpine (steel road bike), 2009 Ti Habenero, 2013 Specialized Roubaix

Mentioned: 399 Post(s)
Tagged: 2 Thread(s)
Quoted: 8916 Post(s)
Liked 159 Times in 102 Posts
Originally Posted by wrr1020 View Post
I should lower my tires, i'm only 145 pounds and usually pump both front and rear to about 110-115.
Correct.
__________________
Originally Posted by rjones28 View Post
Addiction is all about class.
datlas is offline  
Old 04-14-11, 07:33 AM
  #31  
Phantoj
Certifiable Bike "Expert"
 
Join Date: May 2005
Posts: 5,647
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by vision646 View Post
I used his formula but it tells me that I should be riding at 91PSI, my tires are 90max.
for real? 90 or 91 -- there's no real difference.
Phantoj is offline  
Old 04-14-11, 07:52 AM
  #32  
vision646
Senior Member
 
vision646's Avatar
 
Join Date: Dec 2010
Location: Tucson, AZ
Posts: 241

Bikes: Campania Challenger

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Phantoj View Post
for real? 90 or 91 -- there's no real difference.
I'm saying that the maximum pressure on the side wall says 90 PSI, given that should I be using a different calculation? It seems that the equation is assuming you have 120 max PSI tires.
vision646 is offline  
Old 04-14-11, 08:27 AM
  #33  
jfmckenna
Tiocfáidh ár Lá
 
jfmckenna's Avatar
 
Join Date: Dec 2003
Location: The edge of b#
Posts: 5,447

Bikes: A whole bunch-a bikes.

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 279 Post(s)
Liked 2 Times in 2 Posts
Originally Posted by FasterNearGirls View Post
Oh. I should disregard that the maximum on my michelin 23c pro race 3 is lower than the 25s . Again thats just a maximum, I see. I'll ride 100 with both then.
The best thing to do is experiment. You need a good pump with an accurate gauge. As you now know you were way too high so start at 95 front 100 back and move up then down from there. What you want is the optimal road feel for your weight and only you can determine that. You should feel the tire soften over bumps and compress into corners, not chatter, that sort of thing. FWIW I am 205LBS and I typically run 100 front and 110 rear. Different tires can give you different results too so like everything nothing is simple and cut and dry.
jfmckenna is offline  
Old 04-14-11, 10:21 AM
  #34  
motorthings
Senior Member
 
Join Date: Dec 2007
Location: Colorado Springs, CO
Posts: 603
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 49 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
i just pump mine up till they explode, then let 5psi back out. that way i know i am just below the true max.
motorthings is offline  
Old 04-14-11, 10:30 AM
  #35  
Psimet2001 
I eat carbide.
 
Psimet2001's Avatar
 
Join Date: Jan 2006
Location: Elgin, IL
Posts: 20,609

Bikes: Lots. Van Dessel and Squid Dealer

Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 607 Post(s)
Liked 44 Times in 26 Posts
Originally Posted by vision646 View Post
I'm saying that the maximum pressure on the side wall says 90 PSI, given that should I be using a different calculation? It seems that the equation is assuming you have 120 max PSI tires.
No. The listings on the sidewall are a different topic. In general that equation was derived from Sheldon Brown's posted data - I just extrapolated it and did a regression on it. It's not the holy grail but it's worked very well for just about every ride I have worked with.

If it doesn't work for you then so be it.

In general though if you find that you are having to ride around the limits of the tire then it is due to your weight. You should be riding a larger volume tire if you are too heavy. That said there have been a lot of great articles lately expounding on the virtues of larger volume tires. That combined with some of today's wider rim profiles - you're just going to have to experiment with what works well for you.

In general the takeaway for most should be that most riders are riding at too high of a pressure.
__________________
PSIMET Wheels, PSIMET Racing, PSIMET Neutral Race Support, and 11 Jackson Coffee
Podcast - YouTube Channel
Video about PSIMET Wheels

Psimet2001 is offline  
Old 04-14-11, 12:05 PM
  #36  
msu2001la
Senior Member
 
msu2001la's Avatar
 
Join Date: Mar 2006
Location: Midwest
Posts: 403
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 72 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I am 165ish lbs, ride on 23cm tires. I run them between 105-110psi.

This was based mostly on comfort vs. perceived speed. I've tried tires as hard as 120-125psi but the ride is crap. If the psi gets below 90-95, I start to worry about flatting if I hit a bump.

Inferentially, the formula posted above calculates to 107psi for me, so I guess I'm right in the correct range.
msu2001la is offline  
Old 04-14-11, 07:46 PM
  #37  
chinarider
Dan J
 
chinarider's Avatar
 
Join Date: Jul 2006
Location: Iron Mountain, MI
Posts: 1,244

Bikes: 1974 Stella 10 speed, 2006 Trek Pilot 1.2

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by motorthings View Post
i just pump mine up till they explode, then let 5psi back out. that way i know i am just below the true max.
Can I determine my MHR that way?
chinarider is offline  
Old 04-14-11, 09:32 PM
  #38  
Excelsius
Senior Member
 
Join Date: Jan 2011
Posts: 389

Bikes: CAAD10 Rival

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Psimet2001 View Post
No. The listings on the sidewall are a different topic. In general that equation was derived from Sheldon Brown's posted data - I just extrapolated it and did a regression on it. It's not the holy grail but it's worked very well for just about every ride I have worked with.

If it doesn't work for you then so be it.

In general though if you find that you are having to ride around the limits of the tire then it is due to your weight. You should be riding a larger volume tire if you are too heavy. That said there have been a lot of great articles lately expounding on the virtues of larger volume tires. That combined with some of today's wider rim profiles - you're just going to have to experiment with what works well for you.

In general the takeaway for most should be that most riders are riding at too high of a pressure.
So do your formulas include the minimization of rolling resistance? I sure would like to see what data you used and how you extrapolated it to come up with your equation.
Excelsius is offline  
Old 04-14-11, 09:44 PM
  #39  
Butcher
Senior Member
 
Join Date: Sep 2007
Location: Kent, WA
Posts: 495

Bikes: 2005 S-Works SR Equipped,1978 Tom Ritchie Road bike, Kuwahara Tandem

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
With all this talk about high pressures, remember to check the manufacturer of the rim [clinchers]. Several I looked at will not go much past 120psi.
As for going over the max recommended pressures, my tandem is consistantly over the max pressures of my Conti 4000 25c. I have had no problems running 135psi
Butcher is offline  
Old 04-14-11, 09:49 PM
  #40  
Spiduhman
Senior Member
 
Spiduhman's Avatar
 
Join Date: Nov 2007
Location: CenCal - SLO
Posts: 702

Bikes: S2, Wilier GTR (Arr), Giant VT, Myata 3-10

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Likes: 0
Liked 1 Time in 1 Post
If harder is better, run solids.
Spiduhman is offline  
Old 04-14-11, 09:52 PM
  #41  
Spiduhman
Senior Member
 
Spiduhman's Avatar
 
Join Date: Nov 2007
Location: CenCal - SLO
Posts: 702

Bikes: S2, Wilier GTR (Arr), Giant VT, Myata 3-10

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Or, you could try running up and down until you find the spot, like a practical ...person.
Spiduhman is offline  
Old 04-14-11, 09:57 PM
  #42  
oilman_15106
Senior Member
 
Join Date: May 2005
Posts: 6,900
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I have gone to 85psi front and 90psi rear with no loss in speed and a seeming gain in comfort and cornering stability. If those numbers are good enough for Levi they are good enough for me. My weight is 135.
oilman_15106 is offline  
Old 04-14-11, 10:06 PM
  #43  
vandalarchitect
Vandalized since 2002
 
vandalarchitect's Avatar
 
Join Date: Jan 2011
Location: Pullman, WA
Posts: 600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
To get pressure perfect ... take two bathroom scales and a set of rollers. Set one scale under the front and one under the rear. Zero the scales. Put your bike up there and ride as smooth as you can in your typical riding position. Have a friend watch the scales and write down the numbers for front and rear. Calculate the ratio of weight in the front vs. weight in the rear. Add up the total weight of you and your bike. Figure out the magic number in square inches of contact patch for the magic amount of rolling resistance. Use the front to rear ratio, perfect contact patch and the weight of you and your bike and voila! Perfect PSI.
vandalarchitect is offline  
Old 04-14-11, 10:10 PM
  #44  
Excelsius
Senior Member
 
Join Date: Jan 2011
Posts: 389

Bikes: CAAD10 Rival

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Any self reported advantage is likely useless as it's too subjective beyond very rough ranges of PSI. The only consistent and easy comparison test I can think of is rolling down an exact patch of a hill without any pedaling and making sure your weight is exactly the same for each run. Then you need to time yourself each time. The shorter the hill, the more precise the timing must me - need a computer trigger, high speed camera, or a very long hill with an observant person at both ends of the hill.
Excelsius is offline  
Old 04-14-11, 10:23 PM
  #45  
vision646
Senior Member
 
vision646's Avatar
 
Join Date: Dec 2010
Location: Tucson, AZ
Posts: 241

Bikes: Campania Challenger

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Psimet2001 View Post
No. The listings on the sidewall are a different topic...

In general though if you find that you are having to ride around the limits of the tire then it is due to your weight. You should be riding a larger volume tire if you are too heavy...
Ok so the equation is more about ride quality/effectiveness, I thought it was a calculation derating the maximum PSI due to the weight of the rider. I'm 175 lbs riding 27's, I'll just keep filling my tires to a bit below the sidewall max written on my tire (90 PSI) which is close to what I calculated using the equation.

Thanks for clearing that up.
vision646 is offline  
Old 04-14-11, 10:34 PM
  #46  
VA_Esquire
Senior Member
 
VA_Esquire's Avatar
 
Join Date: Nov 2008
Location: Hampton, VA
Posts: 2,364
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I weigh 195lb and run my 23c tires at 120psi........
Does anyone know of a good (without being stupid expensive) pump? Not the style with the lever, but an electronic style.
VA_Esquire is offline  
Old 04-14-11, 11:17 PM
  #47  
foresthill
Senior Member
 
Join Date: Aug 2005
Location: Lafayette, CO
Posts: 1,212

Bikes: MTB: Stumpjumper FSR, Road: De Rosa King 3

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm 170 lbs. I switched from ~ 120 psi to using psimet's formula some years back, and it's been a great improvement. This puts me at 100 / 110 psi front / rear.

Getting a pinch flat on a road bike is pretty hard unless you're running ridiculously low pressures (or you're hopping curbs a lot, i guess.)
foresthill is offline  
Old 04-15-11, 06:42 AM
  #48  
ridethatbike
In the top 42%
 
ridethatbike's Avatar
 
Join Date: Jul 2009
Location: Kansas
Posts: 220

Bikes: Salsa CCC

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm at 182, and have inflated my tires to 105psi as long as I can remember. Even when I weighed 220.
ridethatbike is offline  
Old 04-15-11, 11:34 AM
  #49  
motorthings
Senior Member
 
Join Date: Dec 2007
Location: Colorado Springs, CO
Posts: 603
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 49 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by motorthings View Post
i just pump mine up till they explode, then let 5psi back out. that way i know i am just below the true max.
Originally Posted by chinarider View Post
Can I determine my MHR that way?
is there any other way to do it?
motorthings is offline  
Old 04-15-11, 01:13 PM
  #50  
djb
Senior Member
 
Join Date: Jul 2010
Location: Montreal Canada
Posts: 9,091
Mentioned: 27 Post(s)
Tagged: 0 Thread(s)
Quoted: 1188 Post(s)
Likes: 0
Liked 58 Times in 49 Posts
MHR, hey they did it on House recently, it must be true.
djb is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.