Page 283 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CHAP TER 1 0. 1 Tyres and wheels

D-60443, Frankfurt am Main) are responsible for speci- little steering effort required during parking
fying tyre data. All bodies recognize the publications of and driving;
these two organizations. low running noise.
At the international level, the International Organi-
zation for Standardization (ISO) also works in the field of Durability refers to:
tyre standardization and ISO Standards are translated long-term durability
into many languages. high-speed stability.

Both are tested on drum test stands and on the road.
10.1.1.2 Passenger car requirements Economic efficiency is essentially determined by the
following:
The requirements for tyres on passenger cars and light purchase cost;
commercial vehicles can be subdivided into the following mileage (including the possibility of profile
six groups: regrooving in the case of lorry tyres);
driving safety wear;
handling rolling resistance;
comfort the necessary volume, which determines
service life the amount of room required in the wheel
economy houses and spare-wheel well;
environmental compatibility. load rating.
To ensure driving safety it is essential that the tyre sits Of increasing importance is environmental compatibility,
firmly on the rim. This is achieved by a special tyre bead which includes:
design (tyre foot) and the safety rim, which is the only tyre noise;
type of rim in use today (Figs. 10.1-5 and 10.1-21). Not raw material and energy consumption during
only is as great a degree of tyre-on-rim retention as manufacture and disposal;
possible required, but the tyre must also be hermetically possibility of complete remoulding inherent in
sealed; on the tubeless tyre this is the function of the the construction.
inner lining. Its job is to prevent air escaping from the
tyre, i.e. it stops the tyre from losing pressure. However, The importance of
this pressure reduces by around 25–30% per year, which tyre design, profile design and the ‘radius–width
shows how important it is to check the tyre pressure appearance’ must not be neglected either.
regularly.
In order to guarantee driving safety, the aim is also to
ensure that tyres are as insensitive to overloading and as
puncture-proof as possible and that they have emer- 10.1.1.3 Commercial vehicle
gency running properties which make it possible for the requirements
driver to bring the vehicle safely to a halt in case of tyre
failure. In principle, the same requirements apply for commer-
Handling characteristics include the properties:
cial vehicles as for passenger cars, although the priority of
high coefficients of friction in all operating conditions; the individual groups changes. After safety, economy is
steady build-up of lateral forces without the main consideration for commercial vehicle tyres. The
sudden changes; following properties are desirable:
good cornering stability; high mileage and even wear pattern
direct and immediate response to steering low rolling resistance
movements;
good traction
guarantee requirement of sustained maximum speed; low tyre weight
small fluctuations in wheel load. ability to take chains
Riding comfort includes the characteristics: remoulding/retreading possibilities.
good suspension and damping properties Compared with passenger car tyres, the rolling resistance
(little rolling hardness); of commercial vehicle tyres has a greater influence on
high smoothness as a result of low radial tyre fuel consumption (20–30%) and is therefore an impor-
run-out and imbalances; tant point (Fig. 10.1-32).

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