Morgan SUPERSPORT - Page 70

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Replacement Tyres and Tyre Quality Grading
The tyre quality grade can be found on the tyre sidewall, indicating the quality
of performance of the tyre.
For example: TREADWEAR 240 TRACTION AA TEMPERATURE A.
WARNING Always change at least one axle set at a time.
WARNING New tyres will contain release agent on the outer surface that
may take several miles to clear. Always drive extra carefully on new tyres.
Treadwear
The Treadwear grade is a comparative rating based on the wear rate of the
tyre when tested under controlled conditions on a specied government
test course. For example, a tyre graded 150 would wear one and one-half
(1.5) times as well on the government course as a tyre graded 100. The
relative performance of tyres depends upon the actual conditions of their use,
however, and may depart signicantly from normal due to variations in driving
habits, service practices and dierences in road characteristics and climate.
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Traction
The traction grades, from highest to lowest, are AA, A, B, and C. Those
grades represent the tyre’s ability to stop on a wet surface as measured under
controlled conditions on specied government test surfaces of asphalt and
concrete. A tyre marked as grade C may have poor traction performance.
WARNING The traction grade assigned to this tyre is based on straight
ahead braking traction tests, and does not include acceleration,
cornering, hydroplaning, or peak traction characteristics.
Temperature
The temperature grades are A (the highest), B, and C, representing the tyre’s
resistance to the generation of heat and its ability to dissipate heat when tested
under controlled conditions on a specied indoor labouratory test wheel.
Sustained high temperature can cause the material of the tyre to degenerate
and reduce tyre life, and excessive temperature can lead to sudden tyre failure.
The grade C corresponds to a level of performance which all passenger car
tyres must meet. Grades B and A represent higher levels of performance on
the labouratory test wheel than the minimum required by law.
WARNING The temperature grade for this tyre is established for a tyre
that is properly inated and not overloaded. Excessive speed, under ination,
or excessive loading, either separately or in combination, can cause heat
build-up and possible tyre failure.
The factory-tted tyres on the vehicle are developed using high performance
compounds which become brittle at low temperatures and therefore should
not be used in certain conditions. These tyres should be stored or used only
at temperatures at or above minus 10°C (14° F) to maintain performance
characteristics and avoid damage to the tyre or injury to persons or property.
TYRES