Having owned my '90 since new, I've tried lots of tires and sizes. For street/highway use I've settled on 255-70 x 15. Perfect fit on my 8 x 15 Rally wheels, and diameter is the same as OE 235-75 x 15s so the speedo and odometer read correctly. I recommend BFG Radial T/As, getting over 60,000 miles life.