PSI question

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2008-06-24 6:47 PM

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Subject: PSI question

All things being equal (which I know is impossible to achieve), how much increase in speed could one expect from increasing the pressure in the tire.  Say 100 to 110 PSI?  I 've been told you can run an increased risk of flats with high PSI's especially in hot climates.  I would appreciate any insight.  Thanks!

2008-06-24 7:42 PM
in reply to: #1487765

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Subject: RE: PSI question

You might find this recent thread helpful:

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp?tid=111862&posts=10&start=1

This site has a pretty comprehensive discussion of tires (see the section on pressure reccomendations):

http://www.sheldonbrown.com/tires.html 

Upshot: hard to answer even 'all things being equal' because the answer depends also on:

* road conditions (rolling resistance decreases with pressure more on some surfaces than on others)

* rider weight (decrease of rolling resistance as a function of pressure also depends on rider weight)

* tire material

* tire size (width and diameter)

* speed of travel 

and probably 10 other things that I'm not thinking of.

Practical answer: experiment and see what works for you.  But keep in mind that road conditions can be an important factor in your choice of pressure.

2008-06-24 7:48 PM
in reply to: #1487765

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Subject: RE: PSI question
The quick answer is - Read the sidewall of the tire and look for the "Max PSI." Use that as your guideline. If it allows 110psi, use it. You actually have a decreased risk of pinch flats with higher psi, but if its REALLY hot out, or if you are riding your brakes down a really long hill your rim and tire can heat up causing an increase in pressure and the tire to pop. However... thats VERY uncommon.

For the most part, anything between 100-110 works well for most people. Remember, the reduced pressure will make it more comfortable of a ride too.

Try it out and see what speed gains you get! Thats my suggestion!
2008-06-24 10:01 PM
in reply to: #1487860

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Subject: RE: PSI question

ranger5oh - 2008-06-24 7:48 PM The quick answer is - Read the sidewall of the tire and look for the "Max PSI." Use that as your guideline.  Try it out and see what speed gains you get! Thats my suggestion!

3 sentences says it all.

2008-06-25 11:04 AM
in reply to: #1487765

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Master
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Subject: RE: PSI question
Also, if it's hot out, pump your tires up outside after leaving your bike outside for a few minutes.  The hot pavement will still heat them up more and cause some expansion on your ride, but not as much as if you pumped them up to 120 in your air conditioned house.

Edited by JoshKaptur 2008-06-25 11:04 AM
2008-06-25 11:24 AM
in reply to: #1488059

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Subject: RE: PSI question
Tri-FatBoy - 2008-06-24 11:01 PM

ranger5oh - 2008-06-24 7:48 PM The quick answer is - Read the sidewall of the tire and look for the "Max PSI." Use that as your guideline.  Try it out and see what speed gains you get! Thats my suggestion!

3 sentences says it all.

Unless you're using tubulars. Lots of them have maxes in the 220psi range, and unless you're racing on the track you shouldn't ever pump them up that high.

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