Ford F-650 2008 User Manual page 207

Maintenance and Specifications
If rib tire is used on front axle and lug or off-road type on rear axle
positions:
1. Front (Steering) Axle: Replace tires at front wheels when tread is
worn to 4/32 inch (3 mm) or less.
2. Rear Axles: Tires must be removed when the tread is worn to
2/32 inch (2 mm) or less. Tires identified with the word "re-groovable"
molded on the sidewall can be re-grooved. A minimum of 3/32 inch
(2.5 mm) of under-tread must be left at the bottom of the grooves.
Wheel and tire balancing
Out-of-round or out-of-balance wheels or tires can cause vehicle
vibration, bounce and shimmy. Replace damaged or out-of-round wheels.
Out-of-round tires and wheel assemblies can be corrected by re-clocking
the tire relative to the wheel.
The tire and wheel assembly should then be dynamically balanced.
Wear
Radial tires can exhibit three types of normal wear patterns: 1) Even,
2) Erosion, 3) Chamfer.
Even wear is a sign that the tire is being properly used and maintained.
Erosion wear has also been called rolling wear, channel or river wear.
Erosion wear is found more often at free rolling tires. This is an
indication that the tire is being used in a slow wearing operation. What
happens is that the belt plies are held very rigid and the tread is not
allowed to distort as it passes through the contact area. Wear will only
occur at the edge of the tread. No corrective action required. If erosion
gets to be 1/16 inch (2 mm) or more, the tire may be rotated to a drive
axle.
Chamfer or shoulder wear, with tires inflated properly, is a normal
tendency of most radial tire designs. If both inside and outside shoulders
are wearing evenly around the tire, no further action is required.
Over-inflation is not effective in correcting this effect.
Tires: Irregular Wear
If irregular wear is present, check the axle alignment, tire pressure,
wheel balancing, shock and suspension component condition, and wheel
bearing end play.
This condition not only shortens tire life, but will adversely affect the
handling of your vehicle, which is dangerous.
207
2008 F-650/750 (f67)
Supplement