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06-29-13, 02:05 PM
#13
TejanoTrackie
Veteran Racer

Join Date: Jul 2009
Location: Ciudad de Vacas, Tejas
Posts: 11,151

Bikes: 29 frames + 72 wheels

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OP - you find this tire pressure .vs. tire size and rider weight helpful:

Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33
Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67

Front Pressure = .9*Rear Pressure

So in your case rear tire pressure = (.33 x 250 lbs) + 53.33 = 82.5 + 53.33 = 136 psi, which is probably way more than your tires or rims can handle. Front tire pressure = .9 x 136 psi = 122 psi, which is borderline high, depending on the quality of the tire. Therefore, I'd recommend going with 32mm rear and 28mm front, and inflating them to (.17 x 250 lbs) + 41.67 = 84 psi rear and .9 x [(.33 x 250 lbs) + 33.33 psi] = 104 psi front. Those are approximate numbers of course, but most tires these sizes can handle those pressures.
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