Tire pressure vs rolling circumference

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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not a flippin clue. i guess my 8psi in my tracker tires from 20-60mph gps and speedo verified compared to my 30psi in my tracker tires doing 20-60mph gps and speedo verified is false. :rofl:


This right here proves it. Anyone else is welcome to try it as well.

Adam, there are other reasons why one tire on the dual will wear faster than the other with unequal tire pressure. Circumference change isn't the reasoning.

For one, the tire with more pressure in it is being pressed to the road harder when loaded and the low pressure tire will then skip/slip around turns before the high pressure tire will. This induces cupping just like the front tires do when turning due to scrub. Circumference hasn't changed though, just which tire is seeing more road pressure
 

malibu795

misspeelleerr
Apr 28, 2007
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in the buckeye state
The argument that you and John are making that circumference doesn't change regardless of air pressure.. Is Completely contradicting to what you just said... Due to the reasoning that said tire is going to travel same distance regardless of air pressure.. Therefore there should be no scrubbing or pull to side with lower psi on a spooled/solid axle

What I have said and Goodyear spent most likely substantial $$$ says otherwise..
13' over a mile travel difference for a 41"diameter OTR tire with a 5psi difference at 100psi. Isn't much but is enough to screw up a tire..

Jesse
5psi doesn't effect mine(31.5" OD) like it doesn't a 41" tire.. Mine doesn't start till 20psi difference.. Then it's rather obvious when I get a heavy load... As for CAT eye type tpms
I run too low of psi to use them. I run 70psi in my duals to get an ever tread wear.. 80psi burns the center's out
 

lemay153

New member
Mar 1, 2012
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FYI for you NASA scientists wannabes.
#1 your Goodyear Wranglers aren't wrinkle slicks and your truck ain't no top fuel dragster. So you can throw that comparison out the window.
#2 if you air one tire down that one may actually get more traction then the one aired up, giving you the exact opposite effect of what you are saying. Not all tires are the same.
I see a bunch of angry rednecks here. Chill out!


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Fingers

Village Idiot
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Apr 1, 2008
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The argument that you and John are making that circumference doesn't change regardless of air pressure.. Is Completely contradicting to what you just said... Due to the reasoning that said tire is going to travel same distance regardless of air pressure.. Therefore there should be no scrubbing or pull to side with lower psi on a spooled/solid axle

What I have said and Goodyear spent most likely substantial $$$ says otherwise..
13' over a mile travel difference for a 41"diameter OTR tire with a 5psi difference at 100psi. Isn't much but is enough to screw up a tire..

Jesse
5psi doesn't effect mine(31.5" OD) like it doesn't a 41" tire.. Mine doesn't start till 20psi difference.. Then it's rather obvious when I get a heavy load... As for CAT eye type tpms
I run too low of psi to use them. I run 70psi in my duals to get an ever tread wear.. 80psi burns the center's out


Please read again Adam. I did not say the circumference didn't change with pressure, I said it wasn't significant in an OTR tire. Even for your 41" truck tire example from Goodyear, the change in diameter is 0.085" or 0.2%. or on your 31.5" tire, one good burn out.
 

malibu795

misspeelleerr
Apr 28, 2007
8,240
550
113
42
in the buckeye state
FYI for you NASA scientists wannabes.
#1 your Goodyear Wranglers aren't wrinkle slicks and your truck ain't no top fuel dragster. So you can throw that comparison out the window.
#2 if you air one tire down that one may actually get more traction then the one aired up, giving you the exact opposite effect of what you are saying. Not all tires are the same.
I see a bunch of angry rednecks here. Chill out!


Sent from my iPhone using Tapatalk
Ever seen a wrangler tire on a dyno?
They wrinkle even at full psi. ;)

Please read again Adam. I did not say the circumference didn't change with pressure, I said it wasn't significant in an OTR tire. Even for your 41" truck tire example from Goodyear, the change in diameter is 0.085" or 0.2%. or on your 31.5" tire, one good burn out.

It is Enough to change revolution per mile of the tire by 1-2 rpms
Lower pressure tire shortens its travel distsance by 13' on a 41" tall tire. According to the Goodyear statement.. That is roughly little more then 1 complete revolution slower then the properly inflated tire..
Meaning circumference changes..
It wouldn't surprise me that the study was done after the warrantied alot of tires, and they went to figure out why tires where failing.
 

six5creed

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Jan 6, 2016
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I took this while sitting in the bank drive thru yesterday. Good thing it's not 4WD. Check out those fronts.
 

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todds87ss

New member
Jan 30, 2015
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VW uses the ABS system (input from tire rotation sensor) to determine when there is a tire pressure difference - that is their TPMS system. They do not use individual sensors.
That should be evidence enough that tire pressure changes distance per revolution (and yes, circumference).
 

2004LB7

Well-known member
Dec 15, 2010
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So, why doesn't one or more of us just mark the tire with a line and a corresponding line on the road and and drive a short distance counting the revolutions. do it with a fully inflated tire and under inflated tire and see if there is any differences traveled between the two?
 

six5creed

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Jan 6, 2016
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So, why doesn't one or more of us just mark the tire with a line and a corresponding line on the road and and drive a short distance counting the revolutions. do it with a fully inflated tire and under inflated tire and see if there is any differences traveled between the two?

That would be too easy, it has to be argued about first.
 

Digmax

Member
Jan 23, 2016
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Circumference vs diameter...... this is the argument, forget circumference, diameter is what matters.... flatten the tire, lower the diameter.... slower you go.
 

2004LB7

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Circumference vs diameter...... this is the argument, forget diameter, circumference is what matters.... flatten the tire, circumference stays the same.

Argument can go each way
 

Digmax

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Jan 23, 2016
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Ok, think extremes.10 ft tire, one inch rim, totally deflate tire, now pull ahead one revolution there will be huge wrinkles passing under rim, kinda doubt will travel as far, only thing changed was diameter
 

2004LB7

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I can see an extreme where the tire is wrinkled and passing under the rim, but when we are talking about under pressure of say 30 psi where then is no wrinkling but a noticeable bulge and lower ride. Does it travle the same distance per a revolution as a properly inflated tire?
 

Awenta

Active member
Sep 28, 2014
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Should have done a few more turns to lower the margin of human error. Also they should have deflated all the tires.

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Digmax

Member
Jan 23, 2016
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Close but as soon as you start seeing a bulge in your tire the diameter is less so there is a small difference prob not enough to talk about but still a difference
 

Chevy1925

don't know sh!t about IFS
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Should have done a few more turns to lower the margin of human error. Also they should have deflated all the tires.

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Won't matter. If it changes mph 1-2 by just a few pounds like Adam was saying, a tire that flat should make it very visible.

Like I've said, I've gps verified my tracker at 30psi and 8 psi and there is no difference in mph at speed.