IMPORTANT: Avoid excessive drive train wear. Do not mix worn and new tires, bias and radial, or tires of different diameters. Do not use R2 tires in combination with R1.

With the tire industry converting to metric designations, there are many new terms which can be confusing. To simplify things, tires are placed into groups by their Rolling Circumference Index (RCI). Rolling circumference is the distance a tire travels in one revolution. Tires within a group, regardless of rim size, are the same or nearly the same height. Knowing and understanding RCI and group sizes makes choosin