CHAPTER 2. CARE, MAINTENANCE, AND INSPECTION (Con't)
SECTION I. GENERAL INFORMATION (Con't)
2-11. MATCHING OF TIRES (Con't).
d. Different manufactured tires and different brands
may be mixed on the same vehicle if they fall within certain
tolerances. When the tires are of a different make or there is a
difference in the tread pattern, either the circumference or the
overall diameter should be measured after mounting on the
rim and inflating. Never overinflate or underinflate tires in an
attempt to compensate for tire measurement variations. There
is an allowable tolerance for the matching of dual tires that
should never be exceeded. When dual tires have permissible
difference in measurements (see Table 2-1), the larger size
tire should be mounted outside. Minor variations of tread
designs, as encountered from one manufacturer to another,
may be used providing the sizes and tire constructions (bias
or radial) are compatible. Never mix nondirectional cross-
country (NDCC), commercial, mud-and-snow (M&S), all-
terrain, or regular highway tires on the same axle, regardless
of make, size, or tread wear.
e. Measure circumference at the center of the tread
with a steel tape or other device. Measure overall diameter with a caliper (Item 10, Appendix B). This tool
may also be improvised.
Table 2-1. Permissible Measurement Differences for Dual Tires.
Outside Diameter of Tire
Permissible Differences in:
Inch (es) cm Inch (es) cm
Under 30 inches (76.2) cm)
30 to 40 inch (76.2 to 101.6 cm)
40 to 50 (101.6 to 127 cm)
Over 50 inch (127 cm)
1 1/8 2.86
1 1/2 3.81
1 3/4 4.44
2-12. TIRE INJURIES AND OZONE DAMAGE.
a. Tires are constantly subjected to damage. They are cut by sharp objects and bruised by bad
roads, stones. and road shocks. Tires also deteriorate from ozone exposure, heat, and age. It is dangerous
to drive with a seriously injured or deteriorated tire because it may blowout, causing the driver to lose
control of the vehicle.
b. Remove, repair, or replace tires when a cut or crack is deep enough to have reached the fabric
or when the cord body is exposed (1) . Small cuts or cracks in the tread that do not expose the cord body
(2) need not be repaired; however, they should be periodically inspected for penetration to the cord body.
Tires with a bulge (3) are unserviceable and must be removed and inspected for possible tread separation.