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Old 05-13-2011, 08:07 AM   #1
zerobounds
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Tire pressure technicalities

So i always hear the recommended tire pressure adjustments, cold temps and the rise after heating up through the TD, etc..

What are the effects of pressure too high and too low?

For instance if i'm running 30/30 cold and drop to 29/26 cold what is tire now doing differently that will improve or degrade the capabilities of it? Too much pressure (ie 40/40) will not let the tire flex properly and slip sooner (correct?) but is there a downside to pressures as low as 29/26 or something similar? Why do i want more pressure in front other than the somewhat minor suspension change?

Trying to figure out a little more about the pressures and why i would set them at certain levels, never really got more than basic knowledge about them for track riding.
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Old 05-13-2011, 08:18 AM   #2
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For optimum performance while heeled over on the track, tire manufacturers usually recommend running pressures lower than those reserved for the street. Why? The lower pressure allows for a larger contact patch and therefore more grip in the corners. How low should the pressures be? They shouldn't be so low that they allow the carcass to deform and cause handling problems. Also, if the pressure is too low, the tires could overheat and the extra traction being sought will slip away. In the days of bias-ply tires, setting tire pressure was critical for keeping the tread in the correct operating temperature. Although radial tires have minimized some of the temperature fluctuations caused by pressure sensitivity, setting a tire to the proper pressure will pay off dividends measured in lap times.



Read more: http://www.sportrider.com/tech/tires...#ixzz1MEpXACe8
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Old 05-13-2011, 08:31 AM   #3
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Cory Johnson from Metzeler/Pirelli says between 75 and 80 percent of the tire warranty claims he reviews are caused by underinflation.

Read more: http://www.sportrider.com/tech/tires...#ixzz1MEsaO500
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Old 05-13-2011, 10:50 AM   #4
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Quote:
Originally Posted by zerobounds View Post
So i always hear the recommended tire pressure adjustments, cold temps and the rise after heating up through the TD, etc..

What are the effects of pressure too high and too low?

For instance if i'm running 30/30 cold and drop to 29/26 cold what is tire now doing differently that will improve or degrade the capabilities of it? Too much pressure (ie 40/40) will not let the tire flex properly and slip sooner (correct?) but is there a downside to pressures as low as 29/26 or something similar? Why do i want more pressure in front other than the somewhat minor suspension change?

Trying to figure out a little more about the pressures and why i would set them at certain levels, never really got more than basic knowledge about them for track riding.

Pressure controls tire temp. Ergo:

a lower pressure allows the tire to heat up more. If you run too low of a pressure (within reason...obviously 10 psi is going to cause totally weird handling) you run the risk of overheating the tire which prematurely wears it, and causes a grip reduction as the tire's oils come to the surface and make it greasy.

a higher pressure allows the tire to heat up less. If you run too high of a pressure you run the risk of not being able to warm up the tire enough to get it's max grip, and you will cold tear the tire prematurely wearing it.
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Old 05-15-2011, 12:28 AM   #5
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also remember that not all tire pressure numbers work the same for every rider. even if you're on the same exact tire. it also depends on skill level. for example, a faster and more aggressive rider will tend to run higher pressures because they can generate and keep the heat in the tires better than a less skilled rider can.

less pressure = more contact patch, tire flattens out (effects handling)
more pressure = less contact patch, tire rounds out and takes proper shape (handles better)

it's a give or take, be sure to get a good baseline pressure to start off with, then adjust to how you see fit. even a 1/2 lb. of pressure makes a difference for me now, keep playing with it and get the feel for what tire pressures work better for you.
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