In industrialized countries, cross-ply tyres are no longer used on passenger cars, either as original tyres or as replacement tyre designs , unlike areas with very poor roads where the less vulnerable sidewall has certain advantages. The same is true of commercial vehicles and vehicles that tow trailers, and here too radial tyres have swept the board because of their many advantages. Nowadays, cross-ply tyres are used only for:
- temporary use (emergency) spare tyres for passenger cars (due to the low durability requirements at speeds up to 80 or 100 km h1);
- motor cycles (due to the inclination of the wheels against the lateral force);
- racing cars (due to the lower moment of inertia);
- agricultural vehicles (which do not reach high speeds).
Cross-ply tyres consist of the substructure (also known as the tyre carcass,) which, as the ‘supporting framework’ has at least two layers of rubberized cord fibres, which have a zenith or bias angle x of between 20 and 40 to the centre plane of the tyre . Rayon (an artificial silk cord), nylon or even steel cord may be used, depending on the strength requirements. At the tyre feet the ends of the layers are wrapped around the core of the tyre bead on both sides; two wire rings, together with the folded ends of the plies, form the bead. This represents the frictional connection to the rim. The bead must thus provide the permanent seat and transfer drive-off and braking moments to the tyre. On tube-less tyres it must also provide the airtight seal.
The running tread, which is applied to the outer diameter of the substructure, provides the contact to the road and is profiled. Some tyres also have an intermediate structure over the carcass as reinforcement.
At the side, the running tread blends into the shoulder, which connects to the sidewall (also known as the side rubber), and is a layer that protects the substructure. This layer and the shoulders consist of different rubber blends from the running tread because they are barely subjected to wear; they are simply deformed when the tyre rolls. This is known as flexing. Protective mouldings on the sides are designed to prevent the tyre from being damaged through contact with kerbstones. There are also GGgrooves, which make it possible to see that the tyre designs is seated properly on the rim flange .