Porsche 911 2020, Owner'S Manual

Page: 307 / 360

A
B
C
D
E
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Wheels and Tires
305
Traction AA, A, B, C
The traction grades, from highest to lowest, are AA,
A, B, and C and they represent the tire's ability to
stop on wet pavement as measured under controlled
conditions on specified government test surfaces of
asphalt and concrete. A tire marked C may have poor
traction performance.
Information
The traction grade assigned to this is based on
braking (straight-ahead) traction tests and does not
include cornering (turned) traction, acceleration, hy-
droplaning or peak traction characteristics.
Temperature A, B, C
The temperature grades are A (the highest), B and C,
representing the tire's resistance to the generation
of heat and its ability to dissipate heat when tested
under controlled conditions on a specified indoor
laboratory test wheel.
Sustained high temperatures can cause the material
of the tire to degenerate and reduce tire life, and
excessive temperature can lead to sudden tire
failure.
The grade C corresponds to a level of performance
which all passenger vehicle tires must meet under
the Federal Motor Vehicle Safety Standard No. 109.
Grades B and A represent higher levels of perform-
ance on the laboratory test wheel than the minimum
required by law.
Glossary of tire terminology
Radial ply tire
A pneumatic tire in which the ply cords which extend
to the beads are laid at substantially 90° to the cen-
terline of the tread.
Ply
A layer of rubber-coated parallel cords.
Cord
The strands forming the plies in the tire.
Rim
A metal support for a tire or a tire and tube assembly
upon which the tire beads are seated.
Bead
The part of the tire made of steel wires, wrapped or
reinforced by ply cords, that is shaped to fit the rim.
Sidewall
The portion of a tire between the tread and the bead.
Tread
The portion of the tire that comes in contact with
the road.
Tire pressure plate
A label in the door sill area at the driver’s door pro-
viding information about seating capacity, vehicle
load limit, original tire size and recommended infla-
tion pressure.
Tire Identification Number (TIN)
An identification number on radial tires providing in-
formation about the manufacturer, tire size, tire type
and date of manufacture.
Inflation pressure
A measure of the amount of air in the tire. The tire
pressure is measured in kilopascals (kPa), pounds
per square inch (psi) or bar.
Cold inflation pressure
The tire pressure of a cold tire with ambient tem-
perature maximum 68 °F / 20 °C and the vehicle out
of direct sunlight exposure.
Maximum permissible inflation pressure
The maximum cold inflation pressure to which a tire
may be inflated.
Recommended inflation pressure
The cold inflation pressure found on the tire pressure
plate.
kPa (Kilopascal)
A metric unit for tire pressure.
PSI (Pounds per square inch)
A standard unit for tire pressure.
> Please see chapter "Loading information" on
page 328.
Overloading
DANGER
Overloading
Overloading can lead to dangerous vehicle reactions
and long braking distances.
e
Do not overload your vehicle. Be careful about
the roof load.
e If you plan to load the vehicle, first correct the
tire pressure. Tire pressure for loaded vehicle can
be found on the tire pressure plate and in the
chapter technical data.
e Never exceed the specified axle load.