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

How far under your tire's inflation rating will you go?

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

How far under your tire's inflation rating will you go?

Old 10-30-14, 06:40 PM
  #1  
loimpact
Senior Member
Thread Starter
 
loimpact's Avatar
 
Join Date: Dec 2013
Location: SoCal
Posts: 1,326

Bikes: 2014 Cannondale Supersix Evo 3; 2014 Cannondale Quick 4; 2014 Cannondale Crash 4 hi-mod

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Likes: 0
Liked 1 Time in 1 Post
How far under your tire's inflation rating will you go?

Curious as to what folks might do. I'm currently running Conti GP regulars right now and typically run 110psi rear and 100psi front (700 x 23). I do that cuz I feel it's best for speed for me. (I think mine are rated up to 130 but would never run them that high for comfort's sake)

I recall one shop I test rode a few bikes at this summer always had mushy tires. I *think* they wanted the test rides to be "cushy" so if I had to guess, I'd say they were at around 80psi. But this was all the typical race bikes from C'dale, Spesh, Fuji, Giant, etc.

No way those tires were rated at that so wonder if they'd expect folks to ride like that regularly.

Anywho....I know we've talked a lot about going over but wondered how far "under" folks might go.

TIA
loimpact is offline  
Old 10-30-14, 06:55 PM
  #2  
Igualmente
Senior Member
 
Join Date: Aug 2014
Posts: 360
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I find with 25 and 28mm tires that the minimum pressures are a few psi high for the actual weight on the front tire of my bike. The rear doesn't have the same issue.
Igualmente is offline  
Old 10-30-14, 07:34 PM
  #3  
bengreen79
Allez means go.
 
bengreen79's Avatar
 
Join Date: Jul 2008
Location: Two Rivers, WI
Posts: 894
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I usually fill my 700 x 23's up to 120 and ride it all week. By the next time I fill them up, they might be as low as 80 if there was a lot of temperature changes. I would say 90-100 rides the best for me (no speed difference, more comfortable) but I'd rather not fill them up twice a week.
bengreen79 is offline  
Old 10-30-14, 07:37 PM
  #4  
SevenTwentyNine
Senior Member
 
SevenTwentyNine's Avatar
 
Join Date: Sep 2014
Location: New York, NY
Posts: 415

Bikes: Wheelbarrow

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
My Bontrager clinchers are rated at about 100psi-115psi. I run them at 125psi-130psi rear (depending on how hot it is and how fat I feel that morning) and 125psi front. Upgrading to tubulars and you can bet I'll be in the 150-160psi range. I don't know what comfort is.
Oh how LOW will I run them ... excuse me while I show myself out the door.
SevenTwentyNine is offline  
Old 10-30-14, 07:45 PM
  #5  
zvez
Senior Member
 
zvez's Avatar
 
Join Date: Jul 2013
Location: Columbus, GA
Posts: 536

Bikes: 2014 Cervelo R5 Dura Ace,2014 Specialized S-Works Roubaix

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I ride 100-105 psi, I weigh 160 pounds. No issues with flats or anything. WHen I started riding last year I was running 120 or so but the lower pressure is definitely much more road friendly.
zvez is offline  
Old 10-30-14, 08:21 PM
  #6  
loimpact
Senior Member
Thread Starter
 
loimpact's Avatar
 
Join Date: Dec 2013
Location: SoCal
Posts: 1,326

Bikes: 2014 Cannondale Supersix Evo 3; 2014 Cannondale Quick 4; 2014 Cannondale Crash 4 hi-mod

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by SevenTwentyNine View Post
My Bontrager clinchers are rated at about 100psi-115psi. I run them at 125psi-130psi rear (depending on how hot it is and how fat I feel that morning) and 125psi front. Upgrading to tubulars and you can bet I'll be in the 150-160psi range. I don't know what comfort is.
Oh how LOW will I run them ... excuse me while I show myself out the door.
LOL.....

Actually, if you haven't ready already (and I know it feels like it's got to be counterintuitive) there's lots on how a larger, wider, lower pressure tires has less rolling resistance than the opposite. It does seem weird, but apparently it's true. (Thus mfgrs' move to 25mm tires for roadies)

Even so, I still have days I want to pump up to about 150psi just to feel like I'm riding on uncompromising balloons but......
loimpact is offline  
Old 10-30-14, 08:29 PM
  #7  
SevenTwentyNine
Senior Member
 
SevenTwentyNine's Avatar
 
Join Date: Sep 2014
Location: New York, NY
Posts: 415

Bikes: Wheelbarrow

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by loimpact View Post
LOL.....

Actually, if you haven't ready already (and I know it feels like it's got to be counterintuitive) there's lots on how a larger, wider, lower pressure tires has less rolling resistance than the opposite. It does seem weird, but apparently it's true. (Thus mfgrs' move to 25mm tires for roadies)

Even so, I still have days I want to pump up to about 150psi just to feel like I'm riding on uncompromising balloons but......
Oh I've read, I'm well aware, but with the tires I run, they are faster, more responsive, and corner better (actually maybe not so much on the cornering) with the pressures I run them at - first hand experience.
I currently run 700x23 clinchers ... I stopped taking them up to 140psi when a tire exploded on me once. It was a long walk to an alternative source of transport. Now I keep it at 130psi maximum.

What you'll learn from engineering is that the suggested range of tolerances are very different from actual range of tolerances and stresses many compounds are capable of sustaining.
SevenTwentyNine is offline  
Old 10-30-14, 08:57 PM
  #8  
pdedes
ka maté ka maté ka ora
 
pdedes's Avatar
 
Join Date: Oct 2008
Location: wessex
Posts: 4,423

Bikes: breezer venturi - red novo bosberg - red, pedal force cg1 - red, neuvation f-100 - da, devinci phantom - xt, miele piste - miche/campy, bianchi reparto corse sbx, concorde squadra tsx - da, miele team issue sl - ultegra

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
at ~180, running 95f, 98r on schwalbe ultremos zx.
pdedes is offline  
Old 10-30-14, 09:02 PM
  #9  
hueyhoolihan
Senior Member
 
Join Date: Dec 2010
Location: Above ground, Walnut Creek, Ca
Posts: 6,682

Bikes: 8 ss bikes, 1 5-speed touring bike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
at 160 pounds i ride my 20 thru 25mm tires at anywhere from 75 to 80 PSI.

they are mainly 700c Vittoria Corsa's and Continental Supersonics. two bike ahve some very old and very narrow NOS 27 inchers. i have a pair of touring 28mm Continental Ultra something or other's. i run them at 65PSI. then on my 1x1/4 MTB's, about 60PSI.

Last edited by hueyhoolihan; 10-30-14 at 09:08 PM.
hueyhoolihan is offline  
Old 10-30-14, 09:04 PM
  #10  
Bunyanderman
Senior Member
 
Join Date: Jun 2014
Location: California
Posts: 1,300

Bikes: NeilPryde Alize Raleigh Misceo 2.0

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I had 38mm at about 40psi, no problems and ran very comfortable but felt like I was riding in syrup.
Bunyanderman is offline  
Old 10-30-14, 09:12 PM
  #11  
StanSeven
Super Moderator
 
Join Date: Feb 2005
Location: Delaware shore
Posts: 13,146

Bikes: Cervelo C5, Guru Photon, Waterford, Specialized CX

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 605 Post(s)
Liked 44 Times in 40 Posts
Originally Posted by loimpact View Post
LOL.....

Actually, if you haven't ready already (and I know it feels like it's got to be counterintuitive) there's lots on how a larger, wider, lower pressure tires has less rolling resistance than the opposite. It does seem weird, but apparently it's true. (Thus mfgrs' move to 25mm tires for roadies)
Do a search of the tests and you'll find all of what you said isn't quite right. Wider tires do have less rolling resistance at the SAME pressures as narrower tires. That's key. Then rolling resistance doesn't decrease with less pressure. Youll find tests showing how resistance starts to go up with less pressure in the same tire. So what you do with less pressure is make tradeoffs between comfort and resistance.

Last edited by StanSeven; 10-30-14 at 09:18 PM.
StanSeven is offline  
Old 10-30-14, 10:52 PM
  #12  
znomit
Zoom zoom zoom zoom bonk
 
znomit's Avatar
 
Join Date: Sep 2006
Location: New Zealand
Posts: 3,798

Bikes: Giant Defy, Trek 1.7c, BMC GF02, Scott Sub 35

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 189 Post(s)
Liked 54 Times in 27 Posts
I put a new wheelset on a few years ago and accidentally went out with 60psi in both (25c GP4000s usually 85/90ish).
Best ride ever.
znomit is offline  
Old 10-30-14, 11:04 PM
  #13  
alexaschwanden
Bike rider
 
alexaschwanden's Avatar
 
Join Date: Jun 2010
Location: san jose
Posts: 3,167

Bikes: 2017 Raleigh Clubman

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I usually run the pressure at around 100 psi, but some times for comfort i do 70-80psi.
alexaschwanden is offline  
Old 10-30-14, 11:21 PM
  #14  
gsa103
Senior Member
 
Join Date: May 2013
Location: SF Bay Area
Posts: 4,149

Bikes: Bianchi Infinito (Celeste, of course)

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 630 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I don't usually go under the MINIMUM recommended pressure. I've done it some just to see if it improved the ride.

My MTB is running ~18psi on 26x2.35in tubeless.
My road bike is usually 75/85 f/r on 700x23 road tubeless. If I were on 700x25, I'd definitely be under the minimum pressure.
gsa103 is offline  
Old 10-31-14, 03:15 AM
  #15  
LesterOfPuppets
cowboy, steel horse, etc
 
LesterOfPuppets's Avatar
 
Join Date: Sep 2008
Location: Valley of the Sun.
Posts: 32,645

Bikes: everywhere

Mentioned: 54 Post(s)
Tagged: 1 Thread(s)
Quoted: 4044 Post(s)
Liked 98 Times in 74 Posts
I've had some with a 160 max. Took em up to 120 a couple of times but usually just 95 f, 100 r.
LesterOfPuppets is offline  
Old 10-31-14, 04:13 AM
  #16  
Lazyass
Senior Member
 
Lazyass's Avatar
 
Join Date: Jul 2008
Location: NC
Posts: 8,171

Bikes: Vintage steel, aluminum, modern carbon disc, single speed, MTB's, the works

Mentioned: 58 Post(s)
Tagged: 0 Thread(s)
Quoted: 1912 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by SevenTwentyNine View Post
I stopped taking them up to 140psi when a tire exploded on me once. It was a long walk to an alternative source of transport. Now I keep it at 130psi maximum.
Oh my God.
Lazyass is offline  
Old 10-31-14, 04:28 AM
  #17  
OldsCOOL
Senior Member
 
OldsCOOL's Avatar
 
Join Date: Jul 2004
Location: northern michigan
Posts: 12,457

Bikes: '77 Colnago Super, '76 Fuji The Finest, '88 Cannondale Criterium, '86 Trek 760, '87 Miyata 712

Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 424 Post(s)
Liked 17 Times in 16 Posts
Never. One stone and you are snakebit.
OldsCOOL is offline  
Old 10-31-14, 05:49 AM
  #18  
rm -rf
don't try this at home.
 
rm -rf's Avatar
 
Join Date: Jan 2006
Location: N. KY
Posts: 5,106
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 637 Post(s)
Liked 18 Times in 17 Posts
Originally Posted by StanSeven View Post
Do a search of the tests and you'll find all of what you said isn't quite right. Wider tires do have less rolling resistance at the SAME pressures as narrower tires. That's key. Then rolling resistance doesn't decrease with less pressure. Youll find tests showing how resistance starts to go up with less pressure in the same tire. So what you do with less pressure is make tradeoffs between comfort and resistance.
I think some tire tests run the wheels on spinning metal cylinders. That might not be a good substitute for a rough, flat road surface. But anyway:

Here's a test with Continental GP4000 tires in different sizes. The 25c tires are still lower rolling resistance at "comparable" pressures, for instance: 115 psi for 23c and 100 psi for 25c.

I posted this in another 25c thread.
From slowtwitch.com

Continental's rolling resistance chart is interesting. The 25c rolling resistance is almost 20% worse (.49) at 80 psi than at 116 psi (.41) What units are they using in the chart? It appears to be Crr x 50 kg?

But: the 25c rolling resistance at 87 psi is equivalent to their 23c at about 112 psi. So larger tires can run at lower pressure and still be efficient.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
My tire pressures. I weigh 170 pounds.

23c: 95-100 psi front, 110 rear.
25c: 90 front, 105 rear. So the rear is actually comparably harder than my old 23c was, but it's still comfortable.
25c on rough roads: 85 front, 95-100 rear. Then I'll try to be careful on potholes or rough railroad crossings to avoid pinch flats. And the tires feel a little slower on steering response at these pressures.

Last edited by rm -rf; 10-31-14 at 06:00 AM.
rm -rf is offline  
Old 10-31-14, 06:05 AM
  #19  
rpenmanparker 
Senior Member
 
rpenmanparker's Avatar
 
Join Date: Dec 2009
Location: Houston, TX
Posts: 28,477

Bikes: 1990 Romic Reynolds 531 custom build, Merlin Works CR Ti custom build, super light Workswell 066 custom build

Mentioned: 103 Post(s)
Tagged: 1 Thread(s)
Quoted: 6392 Post(s)
Likes: 0
Liked 9 Times in 9 Posts
Originally Posted by rm -rf View Post
I think some tire tests run the wheels on spinning metal cylinders. That might not be a good substitute for a rough, flat road surface. But anyway:

Here's a test with Continental GP4000 tires in different sizes. The 25c tires are still lower rolling resistance at "comparable" pressures, for instance: 115 psi for 23c and 100 psi for 25c.

I posted this in another 25c thread.
From slowtwitch.com

Continental's rolling resistance chart is interesting. The 25c rolling resistance is almost 20% worse (.49) at 80 psi than at 116 psi (.41) What units are they using in the chart? It appears to be Crr x 50 kg?

But: the 25c rolling resistance at 87 psi is equivalent to their 23c at about 112 psi. So larger tires can run at lower pressure and still be efficient.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
My tire pressures. I weigh 170 pounds.

23c: 95-100 psi front, 110 rear.
25c: 90 front, 105 rear. So the rear is actually comparably harder than my old 23c was, but it's still comfortable.
25c on rough roads: 85 front, 95-100 rear. Then I'll try to be careful on potholes or rough railroad crossings to avoid pinch flats. And the tires feel a little slower on steering response at these pressures.
crr is unitless. The 50 kg refers to the total load on the tire, which determines to tire compression and contact patch size. So these are the results for a 50 kg load.
__________________
Robert

Originally Posted by LAJ View Post
No matter where I go, here I am...

Last edited by rpenmanparker; 10-31-14 at 06:09 AM.
rpenmanparker is offline  
Old 10-31-14, 06:07 AM
  #20  
canam73
Senior Member
 
Join Date: Jun 2007
Location: Haunchyville
Posts: 6,390
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Wait, isn't the date on milk a "sell by" and not "use by" date?
canam73 is offline  
Old 10-31-14, 06:12 AM
  #21  
rpenmanparker 
Senior Member
 
rpenmanparker's Avatar
 
Join Date: Dec 2009
Location: Houston, TX
Posts: 28,477

Bikes: 1990 Romic Reynolds 531 custom build, Merlin Works CR Ti custom build, super light Workswell 066 custom build

Mentioned: 103 Post(s)
Tagged: 1 Thread(s)
Quoted: 6392 Post(s)
Likes: 0
Liked 9 Times in 9 Posts
Originally Posted by canam73 View Post
Wait, isn't the date on milk a "sell by" and not "use by" date?
Not according to my wife.
__________________
Robert

Originally Posted by LAJ View Post
No matter where I go, here I am...
rpenmanparker is offline  
Old 10-31-14, 06:15 AM
  #22  
canam73
Senior Member
 
Join Date: Jun 2007
Location: Haunchyville
Posts: 6,390
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by rpenmanparker View Post
Not according to my wife.
And men and women are equal. Bollocks to that.
canam73 is offline  
Old 10-31-14, 10:12 AM
  #23  
Reynolds 
Passista
 
Reynolds's Avatar
 
Join Date: Jul 2005
Posts: 6,644

Bikes: 1998 Pinarello Asolo, 1992 KHS Montaña pro, 1980 Raleigh DL-1, IGH Hybrid, IGH Utility

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 476 Post(s)
Liked 34 Times in 28 Posts
At 152, I use 95-100 on 23s, but I've tried as low as 80-85, comfortable ride, no problems except for a "soft" feeling.
Reynolds is offline  
Old 10-31-14, 10:25 AM
  #24  
caloso
Senior Member
 
caloso's Avatar
 
Join Date: Jul 2002
Location: Sacramento, California, USA
Posts: 38,241

Bikes: Ridley Excalibur, Gazelle Champion Mondial, On-One Pompino, Specialized Rock Hopper

Mentioned: 59 Post(s)
Tagged: 0 Thread(s)
Quoted: 1918 Post(s)
Liked 302 Times in 166 Posts
I have some Vittoria tubulars that have a 200psi max rating but I typically ride at 60% of that.
caloso is offline  
Old 10-31-14, 03:06 PM
  #25  
popeye
Senior Member
 
Join Date: Nov 2004
Location: Newport Beach, CA
Posts: 1,461

Bikes: S works Tarmac, Felt TK2 track

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 138 Post(s)
Likes: 0
Liked 7 Times in 6 Posts
Originally Posted by hueyhoolihan View Post
at 160 pounds i ride my 20 thru 25mm tires at anywhere from 75 to 80 PSI.

they are mainly 700c Vittoria Corsa's and Continental Supersonics. two bike ahve some very old and very narrow NOS 27 inchers. i have a pair of touring 28mm Continental Ultra something or other's. i run them at 65PSI. then on my 1x1/4 MTB's, about 60PSI.
You're using Supersonics on the road? I have them on my track bike but they are paper thin and I won't even roll them on the street into the velodrome.
popeye 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.