Cormach PUMA Manuel D'utilisation Et D'entretien page 39

UK
the ground, is in a single piece with the sidewalls and so as
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the wheel turns any lexural movements of the sidewall are
transmitted to the tread.
Radial. The carcass consists of one or more plies with the
cords arranged in a radial direction.
5
A radial carcass in the purest sense is relatively unstable; to
make it stable and prevent stray movements of the tread in
the footprint, on the carcass and underneath the tread an an-
nular reinforcing structure generally known as a belt is used.
3
The tread and the sidewall work with different rigidities and
independently, so as the wheel turns lexural movements of
the sidewall are not transmitted to the tread.
1
4 - Loop. This is a loop of metal consisting of several steel
wires. The carcass plies are anchored to the loop.
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5 - Belt. This is a non-extensible circumferential structure con- 12
8
sisting of plies criss-crossed at very narrow angles, located
underneath the tread, in order to stabilise the carcass in the
footprint area.
6 - Centring ridge. This is a small ridge running around the
circumference of the top of the bead groove, which serves as
reference to ensure that the tyre is centred exactly on the rim
after mounting.
7 - Guard ridge. This is a ridge running around the circumference
of the part of the sidewall most at risk of accidental rubbing.
8 - Sidewall. This is the zone between the shoulder and the
centring ridge. It consists of a layer of rubber of varying thick-
ness, intended to protect the carcass plies against knocks
from the side.
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9 - Liner. This is a sheet of airtight rubber blend, vulcanised
onto the inside of tubeless tyres.
5
10 - Filling. A rubber proile, generally triangular in cross-section,
above the loop; it ensures the rigidity of the bead and provides
a gradual compensation of the sudden change in thickness
caused by the loop.
3
11 - Turn-up. This is the edge of the carcass ply which is 7
wrapped around the loop and placed against the carcass in
order to ix the ply in place and prevent it from fraying.
12 - Sole or foot. This is the innermost layer of the tread, in
contact with the belt or, where there is no belt (bias ply tyres),
with the last ply of the carcass.
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13 - Shoulder. The outermost part of the tread, between the
edge and the start of the sidewall.
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14 - Bead. The part where the tyre its onto the rim. The tip
2
of the bead (a) is its inner edge, while the spur (b) is the out-
ermost part of the bead. The base (c) is the zone in contact
with the rim. The cavity (d) is the concave part on which the
shoulder of the rim rests. 10
d
Tube type tyres. Since the tyre must be able to contain the
pressurised air for a relatively long time, an inner tube is used
e
inside the tyre. In this case, the valve used to insert, retain,
4
check and top up the pressurised air forms part of the inner
a
tube itself.
b
c
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