Toyota 2014 Sienna Manual page 820

6-1. Specifications
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Temperature A, B, C
The temperature grades are A (the highest), B, and C, represent-
ing the tire's resistance to the generation of heat and its ability to
dissipate heat when tested under controlled conditions on a speci-
fied indoor laboratory test wheel.
Sustained high temperature 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 passen-
ger car tires must meet under the Federal Motor Vehicle Safety Stan-
dard No. 109.
Grades B and A represent higher levels of performance on the labo-
ratory test wheel than the minimum required by law.
Warning: The temperature grades of a tire assume that it is properly
inflated and not overloaded.
Excessive speed, underinflation, or excessive loading, either sepa-
rately or in combination, can cause heat buildup and possible tire fail-
ure.
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