Chevrolet DB90 Series, Руководство по обслуживанию

Страница: 198 / 242

S ec. 10- 192
WHEEL? AND TIRES
TOE-IN
TOE-OUT
CAMBER
/ / • \ \
SPRUNG OR SAGGING AXLE
t-828 9
r e a r . Whpn to e -in is e x c e ssiv e the tir e w ear show s
feathered edges on in sid e edge of the skid design.
Toe-O ut — The w h eels on the sam e axle are
Figure
1
0 —M ech anical Irregularities
c lo s e r together in the rear than they are in the front.
T ir e w ear show s feathered edges on outside edge
of the skid design.
Camber - - T his d esign ates the tilt of the w heel.
P o sitiv e Camber is when w h eels are c lo s e r together
at point of road contact. N egative cam ber is when
w h eels a re c lo s e r together at top. Too much cam -
b,er r e su lts in e x c e s s iv e w ear on one sid e of tir e .
C astor — T his is the backward tilt of the
a x le or inclination of the kingpin at the top. Too
lit tle c a ste r ca u ses w heel to wander or w eave -
r e su lt, spotty w ear. E x c e ssiv e ca ste r may cause
w h eel "flight” o r shim m y w ear. Unequal ca ster
c a u se s w heel to pull to one sid e , resulting in e x ­
c e s s iv e apd uneven w ear.
Spruijg or Sagging A xle - - E ither of th e se con-
ditions c a u ses uneven distribution of the load. A
sprung oif sagging axle w ill cause the in sid e dual
tir e to carry the greater load.
Tandem and Spread A xle W heels — F a st tir e
w ear often o ccu rs on tandem w h eels b eca u se of
sid e scuffing when the veh icle rounds a curve and
the t ir e s are not moving in a straigh t path. The
sa m e thing happens when spread a x le tir e s are
dragged or pushed sidew ays; for exam ple, while
sp read axle tr a ile r s a re being spotted at or pulled
away from loading docks.
Sprung or T w isted F ram e — W ill cau se rapid
o r uneven tread w ear.
Grabbing B rakes — B rak es out of adjustment
and ou t-of-rou n d brake drums cau se tir e trea d s to
w ear rapidly in sp o ts. O ut-of-round brake drums
u su ally w ear out tir e s in a sin g le spot. Im properly
adjusted b rakes produce se v e r a l worn p la c e s .
Worn w heel b earings, lo o s e radius rods and
U -b o lts, unbalanced w h e e ls, or wobbly w h eels all
r esu lt in uneven and irreg u la r tread w ear.
At fir s t sign of uneven tir e tread w ear, check
and c o r r e ct a ll m echanical ir r e g u la r itie s.
SELECTION OF TIRES
TIRE MATCHING
(R efer to Figure 11)
Unmatched t ir e s on either Tandem D rive U nits
o r Tridei^i D rive U nits w ill cau se tir e w ear and
scuffing dnd p o ssib le dam age to the drive units.
Consequently we recom m end the tir e s be matched
to within lj/8" of the sam e rollin g radius,
%"
of the
sa m e rollin g circu m feren ce.
TANDEM UNITS
IMPORTANT: The four la r g e st t ir e s should
n ev er be in stalled on one driving a x le or the four
s m a lle s t t ir e s on the other driving a x le. Such tir e
mounting w ill cau se an in te r -a x le "fight,"unusually
high a x le lubricant tem p eratu res that re su lt in p re­
m ature lubricant breakdown and p o ssib le co stly
a x le s e r v ic e .
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT