157dB

Tire pressure is tire pressure.
Not that dependent on rim size.
Run the pressure stated on your drivers side
door jam as a start and adjust for tirewear.

tritonpwrd

Thanks to all for your responses. I guess I'll start out somewhere around 37psi and adjust from there using trial and error.

Stoenr

It is actually somewhat dependent on rim size. But more so on the tire size. A lower profile, standard load tire requires more psi to have the load capacity near the OE size.
Rough example, these #'s are not accurate, but just to give you an idea what I mean.

Stock 18"'s at 32 psi have a load capacity of 1532 lbs (thats actually accurate)
Lets say you go to a 275/35/20. That standard load tire at 32 psi only carries 1246 lbs. (thats actually accurate also)

I say standard load, because some tires are extra load rated and can carry more weight at the same pressure.

I would be running 45psi in a standard load 20" tire.

Sidewall psi is only there so you know what not to go over, not what they recommend to run.

06GT4RAD

I run 36PSI in mine

Richard