Porsche 928 S 1986 Driver Manual page 71

Tyres and tyre care
Steel braced radial-ply tyres are high quality
engineering products. The life of your tyres
depends not only on correct inflation and wheel
alignment but also on your style of driving: full
throttle acceleration, very high cornering
speeds and hard braking increase tyre wear.
Moreover, tread wear is greater on rough road
surfaces and in very hot weather. Like the en­
gine, tyres need to be run under the correct
operating conditions at all times. If treated pro­
perly they will be a long lasting safety element
on your car. The following points demonstrate
what is necessary. Your tyres will thank you
for regular care.
Tyre pressure
It is absolutely essential to keep your tyres at
the right pressure.
The tyre pressures are shown in the "Techni­
cal data" and must always be regarded as
minimum pressures!
Always check pressures when the tyres are
cold. Never let air out of hot tyres!
The maximum air pressure of 36 psi stamped
on the tyres only applies to the U.S. classifica­
tion and is not to be confused with normal ser­
vice pressures. In Europe, the tyre can be in­
flated to higher pressures.
Check regularly every 14 days.
Valve caps
Valve caps protect the valve against dust and
dirt as well as leaks. Always screw the caps
firmly into position and replace missing ones
immediately.
Check every 14 days.
Load and speed
Do not overload your car. Never exceed the
specified roof and trailer coupling loads. A
combination of overload + low tyre pressures
+ high speed + high ambient temperatures is
extremely dangerous.
Winter tyres
Do not exceed the maximum speed limit (160
km/h /100 m. p. h. for Μ + S [Q] radial-ply tyres
or 190 km/h /119 m.p.h. for M + S [T] radial-
ply tyres).
An appropriate sticker must be affixed in the
driver's field of vision if the tyre's maximum
speed is less than the car's maximum speed.
Tread
The risk of aquaplaning increases as the tread
depth decreases. Appearance of the wear in­
dicators (webs in tread grooves 1.6 mm high)
should be taken as a signal for early tyre re­
placement.
Check regularly, particularly before and after
long journeys.
Lateral and radial run-out
Take the precaution of having the tyres ba­
lanced in spring (summer tyres) and before
the start of winter (M+S tyres). Note that only
the specified weights may be used for balanc­
ing. (Self-adhesive weights must not come
into contact with cleaning agents as they might
otherwise drop off.) Uneven tread wear indi­
cates that the wheel is not running true. A spe­
cialist should be consulted in such a case.
See also "Wheel alignment".
Uniform tyre wear can be achieved by periodi­
cally changing round the wheels (e. g. after
5000 km / 3000 miles or longer). But only
change the wheels on one side from front to
back and vice versa so that the tyres always
run in the same direction.
Balancing and checking should be performed
by a specialist workshop.
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