Tyre Construction



A tyre is an elastic rubber-cord casing, mounted on the rim of a disk. This is one of the most important parts of the car, since car handling and, accordingly, road safety depend on tyres for the most part.


Tyres also affect fuel consumption and driving comfort. All these factors are determined by the tyre design, consisting of the following basic elements:

  • Carcass
  • Belt
  • Sidewall
  • Tread
  • Bead
  • Inner liner (in tubeless tyres)

 

Carcass

Carcass is the main part of the tyre, which sustains load transferring it to the wheel rim. It comprises polymer threads, has sufficient rigidity and strength. They can be gathered in one or more layers. Depending on the direction of their arrangement, there are following tyre types:


  • Bias tyres. Threads of the carcass are arranged diagonally and cross each other. Their quantity always corresponds to an even number: 2, 4, 6 or 8.
  • Radial tyres. Cord threads are arranged straight from side to side without any crossing. In addition, such tyres have rigid steel belt. Radial tyre design is more widespread. The tyres can be tubed or tubeless. Radial tyres marking includes letter "R" (as indication of tyre construction type, and not a "radius").



The main difference of the radial tyre from the bias one is that, due to its design, such tyre behaves like a caterpillar with less slippage of the tread pattern elements. It reduces wear of the radial tyre in comparison to the bias one by 20-30%, and sometimes even more.

 

Belt

It is a special rigid belt (in a radial tyre) located under the tread. The basis of the belt includes several layers of rubberized metal cord, arranged diagonally (in bias tyres, the breaker, if any, is made of textile material).

Belt increases resistance of the cord to load and absorbs shock, reducing tread slippage.

Sidewall

Sidewall is also one of the major parts of the tyre construction. It protects the cord from external influences and improves driving comfort.

Tread

Tread is a rubber layer with a raised surface, consisting of:

  • Tread cap – central part of the tread pattern, which provides sufficient contact patch.
  • Shoulder – side blocks, which increase rigidity of the entire construction and ensure road-holding ability.
  • Lamellae – narrow slots in the tread pattern elements, which allow separating the water film in order to reduce its surface tension and provide sufficient road grip.
  • Drainage grooves necessary to prevent aquaplaning.



Beads

Tyre design includes another important element – beads. They ensure reliable fitting and bead-to-rim seal (in case of tubeless tyres). The base of beads comprises rings made of rubberized wire.


Inner liner


Inner liner is used in tubeless tyres and is located adjacent to the carcass, from bead to bead. It is made of special gas-tight rubber. Compared to the tube, it is not in a tense state. Therefore, in case of a puncture, air goes out slowly, and the car handling can be maintained, which ensures safety of the driver and passengers.


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