Tire Classifications
Tire Manufacturer's Designation
Tire Designation
1. TIRE SIZE DESIGNATION
Indicating dimensions of tire:
Generally speaking the designation of tires refers to their size in inches and their ply rating (PR).
The size of a tire means the width of and the diameter of the rim (inside diameter of tire), while the ply rating shows the strength of the carcass.
1. Tire width (cross-sectional width)
2. Tire height
3. Cross-sectional height
4. Rim diameter
5. Tire outside diameter
Nowadays the ply rating shows the strength of the tire; it no longer shows the number of layers of cord cloth. Originally the term "ply" did in fact refer to the number of layers of cord cloth, and was therefore an indication of the tire strength. But with the development of new materials, the original cotton cord cloth changed first to rayon and has now been replaced by nylon or steel wire.
This has made it possible to greatly increase the strength without increasing the number of layers of material. Consequently the term "ply rating" has come to be used to indicate the strength of the tire rather than to express the actual number of plies. Stars (*,**,***) are used to indicate the strength of radial tires.
2. STRUCTURE AND FUNCTION OF TIRE
2-1 Conventional Tire
a) Tread
The tread compound used is resistant to abrasions and cuts. Tread patterns give the tire good traction, longer serviceability and higher resistance to cutting.
b) Breaker
Extra layers of rubber-coated cord are placed between the outer plies and the tread. They prevent cuts reaching the ply cords through tread, and absorb shocks.
c) Plies
A tire is composed of several layers of plies, coated on both sides by a rubber compound.
These maintain inflation pressure of the tires supporting load. These plies are made of high tensile nylon cord.
The term "Ply Rating", according to the Tire and Rim Association (TRA), is defined as follows:
"A given tire with its maximum recommended load when used in specific type service. It is an index of tire strength and does not necessarily represent the number of cord plies in the tire."
d) Inner liner
The inner liner is a rubber layer covering the inside from bead to bead of a tubeless tire, corresponding to the tube of an ordinary tube tire. It prevents the loss of inflation pressure of the tire
Tire Selection
3. COMPARISON OF BIAS AND RADIAL TIRES
3-1 Structure and features of tires
