Tires: Testing and Inspection

TREAD WEAR INDICATORS
The original equipment sites have built-in tread wear indicators to show when tires need replacement. These indicators will appear as 12.7 mm (1/2 inch)wide bands when the tire tread depth becomes 1.6 mm (1/16 inch). When the indicators appear in two or mote grooves at three locations, tire replacement is recommended.






IRREGULAR AND/OR PREMATURE WEAR
Irregular and premature wheel has many causes. Some of them are: incorrect inflation pressures, lack of tire rotation, driving habits, arid wheel alignment.

Rotate the tires if the following conditions are noted:
^ Front tire wear is different from rear tire wear.
^ Uneven wear exists across the tread of any tire.
^ Left front and right front tire wear is unequal.
^ Left rear and right rear tire wear is unequal.

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







RADIAL TIRE WADDLE
Waddle is side to side movement at the front anchor rear of the vehicle. It can be caused by a steel belt NOT being straight within the tire or by excessive tire and wheel lateral runout. It is most noticeable at low speed, 8 - 48 km/h (5 - 30 mph). It may also appear as ride roughness at 80 - 113 km/h (50 - 70 mph). Road test the vehicle to see which end of the vehicle has the faulty tire. If the waddle tire is on the rear, the rear end will shake from side to side, or "waddle." From the driver's seat, it feels as though someone is pushing on the side of the vehicle.

If the faulty tire is on the front, the waddle is more visual. The front sheet metal appears to be moving back and forth and the driver feels as though he is at the pivot point. A more time consuming method of determining the faulty tire is substituting tire and wheel that are known to be good.

Follow these steps:
1. Drive vehicle to determine if tire waddle is coming from front or rear.
2. Install tire and wheel known to be good from a similar vehicle in place of those on end of vehicle which is vibrating.
^ If tire waddle cannot be isolated to front or rear; start with rear tires.
3. Road test again.
^ If improvement is noted, install original tire and wheel one at a time until faulty tire is found.
^ If no improvement is noted, install tires known to be good in place of all four. Then, install originals one at time until faulty tire is found.






RADIAL TIRE LEAD/PULL
Lead/Pull is the unintended deviation from a straight path on a level road. Lead is usually caused by:
^ Wheel alignment.
^ Uneven brake adjustment.
^ Tire construction (consistency).

The way in which a tire is built can produce lead. The "Front Wheel Drive Radial Tire Lead Pull Correction Chart" should be used to make sure that the wheel alignment is NOT mistaken for tire lead. Rear tires will NOT cause lead.