What does the R inside a tire mean?

[FrankDella]

The R in the tire model refers to the tire being a radial tire. Radial tires are named after the internal cord fabric arrangement direction, which forms a 90-degree angle with the tread centerline, resembling the meridians on a globe. Below is a detailed introduction to radial tires: Characteristics of radial tires: The crown part of radial tires is reinforced with steel belts, allowing them to withstand greater internal pressure stress. They feature less tread deformation, better ground grip, and stability, making them more suitable for high-speed driving. Nowadays, passenger cars commonly use radial tires. Meaning of tire model codes: Tire types have internationally standardized tire codes, expressed in millimeters to indicate the section width and the percentage of the aspect ratio. These are followed by the tire type code, rim diameter (in inches), load index (permissible load mass code), and permissible speed code.