Tire sizes and ratings: ... which appears on nearly every tire regardless of the type of car it’s installed on. ... On the bottom end of the chart, an R-rated tire is certified for up to 106 mph.

On your example P235/70R15 tire, the P designates it as a standard passenger-car tire, 235 is the section width, 70 is the aspect ratio, R means the tire is of radial construction, and 15 is the ...