Subject: Automobile Engineering

Topic: Suspension, Wheels & Tires

Difficulty: High

Cross ply tube tyres In this type, the ply cords are waven at an angle (30- 40 degree) to the tyre axis. There are two layers which in opposite directions as has been shown in the figure 11.1. However, the chords are not waven like warp & weft of ordinary cloth, because that could lead to rubbing of the two layers & thus produce heat which could damage the tyre material.

Radial Ply type tyres:
In this the ply cords runs in the radial direction i.e. in the direction of tyre axis. Over this basic structure, run a number of breakers strips in the circumferential direction. The material for the breaker strips must be flexible but in extensible, so that no change of circumference take place with change in the amount of inflation. Without the breaker strips, radial plies would give very soft ride, but there will not be any lateral stability. The in extensible breaker strip behaves like a girder in its own plane & provides directional stability. The belts increases the stability rigidity of the tread which improves the cut-resistance of the tyre. They also transmit the torque forces to the radial ply & restrict tyre extension which prevents cutting, cut-growth & cracking.( Fig: 11.2)

Factors affecting tyre life:
i) Inflation
ii) Vehicle maintenance
iii) Manner of driving
iv) Miscellaneous facters: Heat , Position of fixed tyre , Road condition, season