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Old 08-12-03, 11:45 PM   #1
markyman
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What is the Optimum Tire Pressure

I am new into cycling and wanted to know what is the optimum tire pressure in PSI. I have a mountain bike, and my cycling ride usually take me to a paved road, gravel & sand trails, and a bit of rough trails.
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Old 08-13-03, 03:45 AM   #2
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just follow the inflation pressure of the tire...

it is written/labeled on the tire wall.. you won't miss it..

PS: I'm a roadie, I just max out mine.. My tire inflation pressure is 110psi as marked on the sidewall.
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Old 08-13-03, 07:23 AM   #3
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As noted, the tire will have a maximum recommended inflation. I understand that the tire will hold considerable more then this though.

So how much is enough?

Well rolling resistance decreases with increasing tire pressure. But the decrease in rolling resistance gets awfully small after you hit 100 PSI.

Also if you inflate the tire to beyond rock hard, you might compromise the ride a bit.

I am a fairly heavy rider. I put enough pressure in the tire to avoid pinch flats. If the tire deforms significantly under my load, I put some more air in it. About 110 lbs is plenty on a 25 mm tire for me.
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Old 08-13-03, 08:32 AM   #4
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Hi Markyman,

What type of tires are you using (ie. slicks, knobby, inverted tread)? The pressure you run will vary depending on the terrain and tire type. Generally speaking, the smoother the terrain, the higher the pressure, but that is only a very broad guideline.

Paul
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Old 08-13-03, 01:44 PM   #5
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I'm not sure if more pressure always means less rolling resistance. I've seen comments from people who know more than me that say too a lot of pressure may cause a bike to have less consistent contact with the road and this bouncing results in greater losses than a bit less pressure would.

I guess the only way to tell would be to do a number of those tests where you coast down a short hill and then, see how far you go once it flattens out. Even then I see a problem in that speed likely affects how much you might bounce.

For a relatively simple tool, bikes sure can get complicated!

Bob
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Old 08-13-03, 03:11 PM   #6
Dave Stohler
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Quote:
I'm a roadie, I just max out mine.. My tire inflation pressure is 110psi as marked on the sidewall.
Gee, i sure hope you never get hold of a set of Tufo track tubulars-they say 220 psi max!!

Seriously, though-unless you are having a problem with pinch flats, or you weigh a quarter-ton, there really is no need to pump any tire to it's maximum inflation pressure, especially the front tire.

Most of the time, I ride with about 125 in the rear (21mm tubulars), and about 100 psi in the front. I have a touring bike that I keep at 90 psi rear, 75 front (max is 100), and my ATB I usually keep at 65 rear, 50 front.
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