Other letter possibilities are LT for light truck and T for temporary spare. Actually, the prefix letter is optional so it might not be included in all cases. P designates a tire primarily designed to fit passenger cars. Other letter possibilities are LT for light truck and T for temporary spare. We should point out, however, the prefix letter is optional, so it might not be included in all cases.
R means radial tire construction.
Modern Tire Dealer magazine estimates 99.7 percent of the passenger tire market is radial. 17 is the wheel diameter in inches. The range of wheel diameters on today's passenger cars is 12 to 20 inches. An arrow on the sidewall, primarily added for the tire installer, shows the direction that the tire rotates. Without a chart, the load index and speed rating can be unreadable.