What's Cool Top Rated Search Find automotive web sites across Canada. 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.
R means radial tire construction.
15 is the rim diameter in inches. The range of rim diameters on today's passenger cars is 12 to 20 inches. This severe snow service designation is a more stringent requirement than the M and S rating. Directional tires, such as Goodyear's new Aquatred 3, increase the ability of the tread design to disperse water from under the tire for improved wet traction. An arrow on the sidewall, primarily added for the tire installer, shows the direction in which the tire should rotate.