15. Cross – ply
• the construction details are useful to show
how tyre technology has developed.
• Several textile plies are laid across each
other, running from bead to bead in
• The number of plies depends on the size of
the tyre and the load it has to carry.
• The same number of plies is used on the
crown and the sidewalls.
18. Radial – Ply
• Radial – Ply tyres consist of a carcass ply
formed by textile arcs running from one
bead to the other.
• Each ply which is laid in an arc at an angle
of 90 degrees to the direction the tyre
• At the top of the tyre crown (under the
tread), there is a belt made up of several
plies reinforced with metal wire, laid on
top of the carcass ply.
• These crown plies, laid one on top of the
other, overlap at an angle determined by
the type of the tyre.
19. • Remember the tyre tread depth must be not less than 1.6mm over the central
three-quarters of the tyre and must go all the way round the circumference in
an continuous unbroken band with no bald patches anywhere on the tyre tread.
• If radial and cross-ply tyres are fitted to the same vehicle, the radial-ply tyres
must only be fitted to the rear.
• Cross-ply and radial ply tyres must never be fitted to the same axle.
• Tyre pressures must be set to the manufactures recommendations.
• The tread and side wall must be free from large cuts, abrasions or bubbles
22. Comparison of radial and Cross-ply Tyres
Advantages of radial ply Tyres:-
The side walls can be bend readily ,its shock absorbing
capacity is 25% more than bias ply or cross ply.
The breaker strips of radial Tyres act independently of
the wall plies unlike in cross ply where there is no
Lower rolling resistance and hysteresis loss leads to less
23. Longer tread life because of less heat build in Tyre.
Breaking efficiency on wet roads is better because of
greater sidewall flexibility and tread stiffness.
Smaller slip angles and higher cornering power which
results in Better steering characteristics.
While taking turns it has less tendency to distort and lift
off the road from one side.
Larger resistance to punctures ,cuts and impacts in the