Tires and Wheels Preventive Maintenance
– 172 – Y53-6008
Medium Duty (R10/06)
Overinflation: reduces the
tread contact area with the road
surface, concentrating all of the
vehicle weight on the center of
the tread. This causes prema-
ture wear of the tire.
• Too much air pressure reduces the tire tread contact
area and results in rapid wear in the center of the tire. It
also causes tires to run hard and makes them more vul-
nerable to impact and other road hazard damage.
WARNING! Overinflated tires can cause acci-
dents. They wear more quickly than properly
inflated tires and are more subject to punctures,
cracks, and other damage. They could fail and
cause you to lose control of your vehicle result-
ing in an injury accident. Be sure all tires are
inflated correctly according to the manufac-
turer's recommendations.
If overinflation is noted during travel, do not deflate tires. The
increased pressure is caused by temperature build-up during
operation. This condition has been taken into account during
manufacturing of the tires. Allow tires to cool, then recheck
and adjust if necessary.
Tire Loading
WARNING! Do not exceed the load rating of your
tires (molded on the side wall of your tire) or the
maximum vehicle load rating, whichever is less.
Overloading could result in premature tire fail-
ure causing you to loose control of your vehicle
and result in an injury accident. The maximum
vehicle load rating (GVWR) is found on the Tire
and Rim Data label on the driver's door.
Overloading your vehicle is as damaging to the tires as
underinflation. It significantly affects the expected life (total
mileage of a tire). The following chart shows how neglect or
deliberate abuse can affect the life of your vehicle's tires.
TREAD CONTACT
WITH ROAD
00139a
Table 7 Effect of Load Pressure on Tire Life
Vehicle Load Normal 20% Over 40% Over 60% Over 80% Over 100% Over
Tire Pressure Normal 20% Low 30% Low 35% Low 45% Low 55% Low
Expected Total Tire
Mileage
Normal 70% 50% 40% 30% 25%
