The middle of many 50-profile tires will wear faster than the edges, especially with Pirelli P-7s, I've noticed. Seems to be a tire-related thing. Additionally, the rt rear will wear faster than the left rear, probably due to engine torque, so it behooves an owner to interchange the rears now 'n then to even out the wear. 38psi rear is about right for high speed highway driving, with 34 in front. For autocross & track work, 42 front & 46-48 in the rear works well. But we don't drive on the highway with that high pressure- it'll swap fillings in your teeth! The factory recommended pressures were specified for 185-70x 15 fronts & 205 or 215-70x 15 rears, in belted-bias Arrivas, not radial tires, so unless you still run these ancient tires, you'll be well-advised to run more pressure than suggested for better control.