| Avoiding tyre troubles
There are many individual causes of tyre troubles. However, the
three abuses which will cause most problems, and the greatest
costs, are under-inflation, overloading and speeding.
Under-inflation
Surveys by tyre service engineers show that at least 25 per cent
of all tyres examined are under-inflated by more than 10 per cent.
Neglect of inflation pressures is one of the principle causes
of rapid shoulder wear, uneven tread wear and premature tyre failure
and it is an abuse which surveys show to be on the increase. (NB:
It should be stressed that over-inflation may also result in inferior
vehicle handling, excessive tyre wear and premature failure.)
Overloading
Loading cars, light vans and lightweight trailers above what
they are designed to carry is illegal. It is also likely to put
excessive strain on the tyres resulting in greater than normal
deflection and overheating which, in turn, leads to more rapid
wear, greater susceptibility to impact damage and the danger of
premature failure. (NB: The vehicle Handbook will give increased
inflation pressures for full load conditions.)
Speeding
Travelling for long distances on motorways at sustained high
speeds and generally exceeding statutory speed limits imposes
strenuous demands on tyres especially in terms of heat generation.
Tyres in good condition and correctly inflated are designed to
withstand the heat build-up at their maximum rated speeds. However,
if inflation pressures are significantly below those recommended
then excessive heat will be generated, and in consequence wear
will be accelerated and deflection will be greater with the risk
of premature, and sometimes catastrophic, failure.
Proper care and maintenance of tyres will reward drivers and
vehicle owners with greater safety, better road holding, more
comfort and, ultimately, savings in cost. It will also save them
from the risk of severe penalty (ie fines and driving licence
penalty points) should they be caught on the road with tyres which
do not conform to legal requirements.
This section explains the main legal requirements for the condition
and maintenance of tyres, and gives advice on tyre care to achieve
longer life and lower operating cost.
What the law requires
It is important to understand what the law requires in regard
to the condition and care of tyres. Regulations govern many aspects
of tyre condition of which the following are the principal points:
1. Tyres must be suitable (ie of the correct type and size)
for the use to which the vehicle is being put and must be inflated
to the vehicle or tyre manufacturers' recommended pressures.
2. Tyres of different types must not be fitted to opposite wheels
of the vehicle (for example, radial-ply tyres must not be fitted
to a wheel on the same axle as wheels already fitted with cross-ply
tyres and vice versa, and a two-axle vehicle with single rear
wheels must not have radial ply tyres on the front axle if cross
ply tyres are fitted to the rear axle).
3. No tyre must have a break in its fabric or a cut deep enough
to reach the body cords. No cut must be more than 25mm or 10 per
cent of the tyre's section width in length, whichever is the greater.
4. There must be no lump, bulge or tear caused by separation or
partial fracture of its structure, neither must any portion of
the ply or cord structure be exposed.
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