Pontiac 2006 GTO Owner's Manual page 250

High Speed Operation
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CAUTION:
Driving at high speeds, 100 mph (160 km/h) or
higher, puts an additional strain on tires.
Sustained high-speed driving causes
excessive heat build up and can cause sudden
tire failure. You could have a crash and you or
others could be killed. Some high-speed rated
tires require inflation pressure adjustment for
high speed operation. When speed limits and
road conditions are such that a vehicle can be
driven at high speeds, make sure the tires are
rated for high speed operation, in excellent
condition, and set to the correct cold tire
inflation pressure for the vehicle load.
5-60
Vehicles equipped with 245/45ZR17 95W size tires, do
not require additional air pressure for high-speed
operation. If your vehicle has 235/40ZR18 91W size
tires, use the following chart to determine the cold tire
inflation pressure when operating your vehicle under
high-speed conditions.
Tire Size: 235/40ZR18 91W Recommended Cold
Tire Inflation Pressure for High Speed Operation
Occupant and Cargo
Weight:
470 lbs (210 kg) or less
Front
Rear Tires
Tires
36 psi 36 psi
(250 kPa) (250 kPa)
When you end high-speed driving, return the tires to the
cold inflation pressure shown on the tire and loading
information label.
Occupant and Cargo
Weight:
Up to 740 lbs (330 kg)
(Vehicle Capacity
Weight)
Front Tires Rear Tires
39 psi 44 psi
(270 kPa) (300 kPa)