Tires: Testing and Inspection

IRREGULAR AND PREMATURE WEAR





Irregular and premature tire wear has many causes. Some of them are: incorrect inflation pressures, lack of regular rotation, driving habits, or improper wheel alignment. If wheel alignment is reset due to tire wear condition, always reset toe as close to zero degrees as the specification allows.

If the following conditions are noted, rotate the tires:
^ Front tire wear is different from rear.
^ Left and right front tire wear is unequal.
^ Left and right rear tire wear is unequal.

Check wheel alignment if the following conditions are noted:
^ Left and right tire wear is unequal.
^ Wear is uneven across the tread of any front tire.
^ Front tire treads have a scuffed appearance with "feather" edges on one side of the tread ribs or blocks.

TREAD WEAR INDICATORS





The original equipment tires have built-in tread wear indicators to show when tires need replacement. These indicators will appear as bands when the tire tread depth becomes shallow. When the indicators appear in three or more grooves at six locations, tire replacement is recommended.

RADIAL TIRE LEAD/PULL





"Lead/Pull" is the deviation of the vehicle from a straight path on a level road with no pressure on the steering wheel.

Lead is usually caused by:
A. Incorrect alignment.
B. Uneven brake adjustment.
C. Tire construction.

The way in which a tire is built can produce lead in the vehicle. An example of this is placement of the belt. Off center belts on radial tires can cause the tire to develop a side force while rolling straight down the road. If one side of the tire is a little larger diameter than the other, the tire will tend to roll to one side. This will also cause the tire to develop a side force which can produce vehicle lead.

The radial tire lead/pull diagnosis chart should be used to make sure that front wheel alignment is not mistaken for tire lead.
1. Part of the lead diagnosis procedure is different from the proper tire rotation pattern currently in the owner and service manuals. If a medium to high mileage tire is moved to the other side of the vehicle, be sure to check that ride roughness does not develop.
2. Rear tires will not cause lead.