I have a set of 20s 255 35 20 in the front and 285 30 20 in the rear what should the tire presure be.

 

Probably somewhere between 32-35 psi is good. Check your tire pressure ratings on the sidewall.

 

You should probably stick with the recommended OEM tire pressure (35psi) or close to it.
C.

 

thanks guys

 

The tire pressure listed on teh sidewall of the tire is the maximum pressure recommended for the tire not to fail, NOT the recommended tire pressure. Proper tire pressure varies from vehicle to vehicle.

As to what tire pressure that should be used, experiment with what you like. There isn't a perfect tire pressure; it all has to do with handling characteristics (mainly the difference between the front and rear) and ride quality. I'd start with 35 PSI, drive on it for a day or so, and then adjust up and down to see what you like.