Definition of Casing

The tyre casing comprises the entire main structural body of a tyre, often called the carcass.

Tyre casings include the materials under the tread, the sidewall and steel belts. The tyre casing is the inner structure of the tyre, reinforced in the manufacturing process, with the layers of rubber-coated plies made of polyester, nylon, rayon or steel, that comprise the resistant structure of the tyre upon which the tread, belts, bead, and sidewall are laid.

A simple radial casing is unstable so a belt is put on the radial casing under the tread to reinforce the tyre casing.