Porsche Boxster Owner's Manual page 249

Tire wear
The original equipment tires on your Porsche have
built-in tire wear indicators. They are molded into
the bottom of the tread grooves and will appear as
approximately 1/2 in. (12 mm) bands when the tire
tread depth is down to 1/16 of an in. (1.6 mm).
When the indicators appear in two or more
adjacent grooves, it is time to replace the tires.
We recommend, however, that you do not let the
tires wear down to this extent. Worn tires cannot
grip the road surface properly and are even less
effective on wet roads.
In the United States, state laws may govern the
minimum tread depth permissible. Follow all such
laws.
Danger!
Driving on worn tires can result in loss of
control of the vehicle and could cause serious
personal injuries or death.
Do not drive with worn tires or tires showing
cuts or bruises as they may lead to sudden
deflation and loss of control which could cause
severe personal injury.
Specialized high performance tires on high
performance sports cars exhibit more wear
than those on a family sedan, or even a high
performance sedan. Therefore, it is important
to check your tire pressure and condition at
least every two weeks.
If you notice that tires are wearing unevenly,
consult your Porsche dealer. Uneven wear may
not always be due to improper wheel alignment. It
can be the result of individual driving habits such as
cornering at high speeds. If the tire pressure is not
checked and adjusted regularly, abnormal tire wear
can also occur.
Tire care
Avoid damaging tires and wheel rims.
If you must drive over a curb or other obstacle,
drive slowly and at an obtuse angle.
Check tires for uneven wear and damage
before driving off.
Remove imbedded material.
Replace worn or damaged tires immediately.
Keep oil, fuel, brake fluid, etc. away from tires.
Replace missing valve stem caps.
Keep tires inflated correctly.
Wash tires when washing the vehicle. Also
clean inner side of wheels.
Do not use abrasive cleaners when washing
the wheels.
Check wheel rims for corrosion.
Remove road salt, if driving in winter.
Tire damage, puncture
Check tires for imbedded material, cuts,
punctures, cracks and bulges (side wall)
before driving off.
In case of tire damage, where it is uncertain
whether there is a break in the ply with all its
consequences or tire damage caused by thermal
or mechanical overloading due to loss of pressure
or any other prior damage, we recommend that the
tire be replaced for safety reasons.
If one faulty tire is replaced it should be noted that
the difference in tread depth on one axle must not
exceed 30 %. Handling inconsistencies may result.
Perform a visual inspection if necessary.
Danger!
Risk of serious personal injury or death.
Driving the vehicle with low tire pressure
increases risk of a tire failure and resulting
loss of control. Furthermore, low tire pressure
increases rate of wear of the affected tires.
Check tires - including sidewalls - regularly for
foreign bodies, nicks, cuts, cracks and bulges.
Practical Tips, Emergency Service
247