12—WHEELS AND TIRES
CHRYSLER SERVICE MANUAL
27.
TIRE THUMP
Tire thump is a pounding action that occurs
each time a tire rotates. In most instances, tire
thump is evident at speeds under 45 miles per
hour on a smooth road, and is usually restricted
to a small speed range. If the thump is slight
and difficult to detect, the condition may be
considered acceptable, and tire life will not be
affected.
When checking for cause of tire thump, in-
spect all tires for uneven wear, and make sure
the beads of all tires are properly seated in
the wheel rims. Inflate all tires to 50 pounds
pressure. This will eliminate or reduce thump,
if it is due to tire irregularities.
Drive the car on a smooth road. If the thump
still occurs while the tires are inflated to 50
pounds, the condition is caused by factors, such
as brake drum circle eccentric in relation to
center line of axle, wheel retaining bolt circle
eccentric in relation to the wheel rim, large
patch in tire, or excessive universal joint an-
gularity can cause a condition similar to tire
thump or roughness. However, if thump dis-
appears when tires are inflated to 50 pounds
pressure, make the following test:
Deflate one tire to 25 pounds and drive car
on smooth road. If thump appears, the deflated
tire is at fault. Repeat test until all tires, in-
cluding spare, have been checked. Only one tire
at a time should be deflated to 25 pounds pres-
sure for testing. Reinflate the tire already
tested before proceeding to the next tire.
NOTE
Sometimes, a thumping tire will operate satis-
factorily when changed from one side of the
car to the other. This changes the direction of
the tire's rotation. In severe cases of tire thump,
it may be necessary to replace the tires in ques-
tion.
28.
TIRE WEAR
Inflate tires to proper pressure recommended
in Data and Specifications. (Refer to Fig. 13).
When tires are under-inflated, excessive wear
occurs at the two tread ribs next to the inner
and outer shoulder ribs. Wear occurs at center
of tread when tire is driven over-inflated.
a. Spotty Wear (Fig. 14) usually becomes
evident on front tires when tires are not rotated
every 3,000 miles.
b.
Excessive toe-in or toe-out (Figs. 15 and
16) of front wheels affects the rate of tire wear
more than any other factor.
c. (Refer to Fig. 17). Excessive positive
camber will develop noticeable wear on the out-
er ribs of tires. Excessive negative camber will
result in noticeable wear on the inside ribs.
d. Check for wheel wobble. Straighten or
replace wheel, if necessary.
e. Check for worn ball joints. Replace as
necessary.
f. Check for wear caused by sustained high
speed driving, and driving around corners too
fast.
g. Check for over-inflation (Fig. 18).
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