Glossary - Corghi A 222 Manuel D'utilisation

13. GLOSSARY

Tyre
A tyre consists of: I-the actual tyre, II- the rim
(wheel), III-the air chamber (in tube type tyres),
IV-pressurised air.
The tyre must:
- withstand a load,
- ensure driving power,
- steer the vehicle,
- aid handling and braking,
- aid vehicle suspension.
I - Tyre The actual tyre is the main part of the
overall tyre in contact with the road and is therefore
designed to withstand internal air pressure and all
other stress arising from use.
A tyre section shows the various parts it consists of:
1 - The tread. This is the part in contact with the ground
when the tyre rolls. It comprises a rubber compound
and a "pattern" that is suitable for ensuring good
resistance to abrasion and good grip in dry and wet
conditions, as well as quiet operating conditions.
2 - Edge or bracing. This is a metal fabric or textile
insert, in the area of the outer bead part. It protects
the casing plys from rubbing against the rim.
3 - Casing. This is the resistant structure and comprises
one or more layers of rubber plys. The way the plys
comprising the casing are arranged give the structure
its name. The following structures are possible:
Conventional: the plys are inclined and arranged so
that the strands comprising a ply overlap with those
of the adjacent ply. The tread, which is the part of
the tyre in contact with the ground, is part of the
sidewalls and so during rolling, sidewall flexure is
transmitted to the tread.
Radial: the casing consists of one or more plys with
the cords in a radial direction.
A radial casing in itself is quite unstable. To make
it stable and prevent bad tread movement in the
area of contact with the ground, the casing and the
undertread are reinforced with an annular structure,
usually called belt. The tread and sidewall work with
different, independent rigidities, so during rolling,
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