Chevrolet 10 Series 1970, Service Manual

Page: 538 / 671

WHEELS AND TIRES 10-8
SERVICE OPERATIONS
W h e el N u t Torques (See Specifications)
10-30 S eries
On a new v e h icle o r a fte r the wheel has been changed,
the wheel nut torque must be checked at 100, 1,000 and
6.000 m iles and e v e ry 6,000 m iles th e re a fte r.
40-80 S e rie s and H eavy Duty W heels on 30 S eries
On a new ve h ic le o r a fte r the wheel has been changed,
the wheel nut torque must be checked at 100, 500 and
1.000 m ile s and e v e ry 1,000 m iles th e re a fte r.
Correcting Irregular Tire W e a r
H eel and T o e W e a r - - T h is is a saw-toothed effect w here
one end o f each trea d block is w orn m ore than the other.
Th e end that w ea rs is the one that fir s t grip s the road
when the brakes a re applied.
H eel and toe w ear is le s s noticeable on r e a r tir e s than
on fron t t ir e s , because the p ro p ellin g action of the re a r
w heels c re a te s a fo r c e which tends to w ea r the opposite
end of the trea d blocks. The two fo r c e s , p ro p ellin g and
braking, make fo r m ore even w ear o f the re a r tir e s ,
w hereas only the braking fo r c e s act on the fron t w heels,
and the saw -tooth e ffe c t is m ore noticeable.
A certain amount of heel and toe w ear is n orm al. E x ­
c e s s iv e w ea r is usually due to high speed d rivin g and e x ­
ce s s iv e use of b rak es. T h e best rem edy, in addition to
cautioning the owner on his d rivin g habits, is to in te r ­
change tir e s reg u la rly .
Side W e a r - - T h is may be caused by in c o rre c t wheel
cam ber, underinflation, high cam bered roads o r by taking
co rn ers at too high a rate of speed.
T h e fir s t two causes a re the most common. C am ber
w ea r can be rea d ily iden tified because it occurs only on
one side of the trea d s, w hereas underinflation causes
w ear on both sid es. C am ber w e a r req u ires co rre c tio n of
the cam ber f ir s t and then interchanging t ir e s .
T h e re is, of cou rse, no c o rre c tio n fo r high cam bered
roads. C orn erin g w ea r is discussed fu rth er on.
M isalignm ent W e a r --T h is is w ea r due to e x c e s s iv e
to e -in o r toe-ou t. In eith er case, tir e s w ill re v o lv e with
a side motion and scrape the trea d rubber o ff. If m is ­
alignm ent is s e v e re , the rubber w ill be scraped o ff of
both tir e s ; if slight, only one w ill be affected .
Th e scraping action against the face o f the t ir e causes
a sm all fea th er edge of rubber to appear on one side of
the tread and this feath er edge is certain indication of
m isalignm ent. The rem edy is readjusting to e -in , o r r e ­
checking the entire front end alignm ent if n ecessa ry.
Uneven W ea r--U n even o r spotty w ear is due to such
ir r e g u la r itie s as unequal ca s te r o r cam ber, bent front
suspension parts, ou t-of-balance w heels, brake drums
out o f round, brakes out of adjustment o r other m echani­
cal conditions.
Th e rem edy in each case consists of
locating the m echanical d efect and c o rre c tin g it.
C orn erin g W ear--W h en a truck makes an extrem ely
fast turn, the weight is shifted fro m an even loading on
a ll w heels to an abnormal load on the tir e s on the outside
o f the curve and a v e ry light load on the inside tir e s , due
to cen trifu gal fo r c e . T h is unequal loading may have two
unfavorable resu lts.
F ir s t, the r e a r t ir e on the inside of the cu rve may be
re lie v e d of so much load that it is no lon ger geared to
the road and it slip s, grinding o ff the tread on the inside
half of the t ir e at the ex c e s s iv e rate. T h is type of tir e
shows much the sam e appearance of tread w ea r as tir e
w ear caused by n egative cam ber.
Second, the tra n s fe r of weight may also overload the
outside t ir e s so much that they are la te ra lly distorted
resu lting in ex c e s s iv e w ear on the outside half o f the tir e ,
producing a type of w ear lik e that caused by e x c e s s iv e
p o s itiv e cam ber.
C orn erin g w ea r can be most ea sily distinguished fro m
abnorm al cam ber w ear by the rounding o f the outside
shoulder o r edge of the t ir e and by the roughening of the
tread su rface which denotes abrasion.
C orn erin g w ea r often produces a fin o r ra ised portion
along the inside edge of each row in the trea d pattern.
F ig . 2 — Front W hee ls and A tta ch m e n ts
CHEVROLET TRUCK SERVICE MANUAL