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      06-29-2012, 03:24 PM   #9
Brigadier General

Drives: 11 spc gry m3 e90, 07 X5
Join Date: Jan 2010
Location: chicago

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Originally Posted by walsh
Just want to put this out there for everyone asking about different tire pressures based on wheel and tire size. PSI = pounds per square inch(yes... I'm sure you all know this), its a ratio. So 35 psi is the same "tire pressure" no matter what size wheel or tire you have. Lets do some simple(not realistic tire) numbers for everyone.

Lets say the internal area of your tire is 100 square inches, to get 10 PSI you put in 10 lbs of pressure.

Now lets say you go to a wider tire with the same height. The internal area will naturally increase, to say 120 square inches. To get 10 PSI you now need 12 lbs of pressure.

Since PSI is a pressure to area ratio, it automatically takes care of the pressure increase/decrease for a difference in tire size.

The difference in PSI from car to car is based on the load carried as well as the purpose of the car. But in general most cars range from 28 PSI to 36 PSI.

But as others have said...
I was just thinking this, size doesn't matter this time, everything else does
mods: akra evo, dinan 3.45 diff, ess akra tune, dinan stg.3, Alcon bbk, HRE P40