I running 18x8.5 front and 18x9.5 rear wheels with 235/40 and 255/40. I put 32 psi on all 4 tires and the ride is very rough. My dash is now rattling. Before I was running wider wheels with the same tire set up with more pressure in the tires and the ride is not that rough. What is the proper tire pressure for these size wheels and tires set up?

 

First, why did you go with a 255 and not a 275 in the rear? Your stagger (for VDC if you have it) and speedo are going to be off.

Second, 35psi is the recommended cold pressure. You must have some very stiff sidewalls on the brand tire you bought.