Usa Tyre Gradings; Tread Wear; Traction; Temperature - Aston Martin V8 Vantage Workshop Manual

Road Wheels and Tyres (04.04)
Suspension (04.00)

USA Tyre Gradings

The following information relates to the tyre grading system
developed by the National Highway Traffic Safety
Administration which grades tyres by tread wear, traction
and temperature performance.

Tread Wear

Tread wear grade is a comparative rating based on the wear
rate of the tyre when tested under controlled conditions
(specified government test course). For example, a tyre
graded 150 would wear one and a half times less on the
government course than a tyre graded 100. Relative
performance of the tyres depends upon actual conditions of
use and may depart significantly from normal due to
variations in driving habits, service practices and differences
in road characteristics and climate.

Traction

Traction grades, A (highest), B and C represent a tyre's ability
to stop in wet conditions measured on specified government
test surfaces of asphalt and concrete.
PDI Inspection.
Traction grade is based on braking (straight ahead)
traction tests and does not include cornering (turning)

Temperature

Temperature grades, A (highest), B and C, represent a tyre's
resistance to the generation of wear and its ability to
dissipate heat when tested under controlled conditions
(specified indoor laboratory test road wheel). Sustained high
temperature can cause the material of a tyre to degenerate
and reduce tyre life; excessive temperatures can lead to
sudden tyre failure. Grade 'C' corresponds to a level of
performance which all passenger vehicle tyres must meet
under Federal Motor Vehicle Safety Standard No. 109.
Grades 'B' and 'A' represent higher levels of performance
than the minimum required by law.
Temperature grade is established for a tyre that is
properly inflated and not overloaded. Excessive speed,
under inflation or excessive loading, whether
separately or in combination, can cause heat build-up
and possible tyre failure.
Aston Martin grade as follows:
Tyre Grade
Tread Wear
Traction
Temperature
4-5-2
Warning
traction.
Warning
Level Achieved
140
A
A

Maintenance

Factory installed tyres and road wheels are designed to
operate satisfactory when inflated to the recommended
inflation pressures (Refer to 'Inspection and Verification',
page 4-5-3). The recommended pressures apply to vehicle
loads up to and including the full-rated load capacity.
Correct tyre pressures and driving technique have an
important influence on tyre life. Heavy cornering,
excessively rapid acceleration and unnecessary sharp
braking increase tyre wear.
Replacement tyres should follow the recommended:
• Size
• Speed rating
The use of any other size or type may seriously affect:

• Safety

• Ride
• Handling
• Speedometer and
Odometer calibration
Wheels need to be renewed when:
• Impact damaged
• Heavily corroded
• Porous
Safety
Do not mix different types of tyres on the same vehicle.
Handling may be seriously affected resulting in loss of
Ensure that tyres are mounted with the sidewall
marking 'Outside' showing on the outer sidewall face.
Correct tyre rotational direction is critical.
A tyre and wheel must always be correctly matched.
Wider or narrower tyres than recommended could
cause danger through sudden deflation.
When changing a wheel, make sure that the vehicle
cannot move. Always apply the parking brake and
select the transmission park position (Automatic
Never run the engine with one wheel off the ground,
for example, when changing the wheel. The wheel
resting on the ground may cause the vehicle to move.
Always tighten the wheel nuts to specification. Too tight
may cause damage, too loose may allow the wheel to
Workshop Manual
• Load range
• Radial construction type
• Vehicle ground clearance
• Tyre clearance between
body and chassis
• Wheel bearing life
• Brake cooling
• Wheel stud holes or seats
become damaged
• They have excessive
radial or lateral runout.
Warning
control.
Warning
Warning
Warning
transmission only).
Warning
Warning
become detached.
October 2005