Hello, I have a 1995 750iL with Pirelli Pzero 255/35/20 front and 285/35/20 rear. When I bought them from the original owner, he said to inflate all four tires to 40psi. I'm thinking that the rears should have a higher psi than the fronts? What do you guys think? I also have a sound system that adds about 80lbs to the car. The wheels are Hartage 14-spoke. Thanks.