GMC 2008 Canyon - Manual (Page 324)

High-Speed Operation
{ 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.
If your vehicle has P235/50R18 size tires, they will
require inflation pressure adjustment when driving
your vehicle at speeds of 100 mph (160 km/h) or
higher. Set the cold inflation pressure to the maximum
inflation pressure shown on the tire sidewall, or
35 psi (241 kPa), whichever is lower. See the
example following. When you end this high-speed
driving, return the tires to the cold tire inflation pressure
shown on the Tire and Loading Information label.
See Loading Your Vehicle on page 4-32 and
Inflation - Tire Pressure on page 5-62.
Example:
You will find the maximum load and inflation pressure
molded on the tire’s sidewall, in small letters, near
the rim flange. It will read something like this: Maximum
load 690 kg (1521 lbs) 300 kPa (44 psi) Max. Press.
For this example, you would set the inflation pressure
for high-speed driving at 35 psi (241 kPa).
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