Chevrolet BEAUVILLE SPORTVAN G10 SERIES, Руководство по обслуживанию

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BRAKES 5-15
S m o o th up any slight scores by polishing w ith fine em ery
cloth. Heavy or extensive scoring will cause excessive brake
lining w ear, and it will pro b ab ly be necessary to refinish in
o rder to true up the braking surface.
I f the brake linings are slightly w orn and th e drum is
grooved, the drum should be tu rn e d ju st enough to remove
grooves. The ridges in the lining should be lightly rem oved
w ith a lining grinder.
I f brake linings are m ore than h a lf w orn b u t do not need
replacem ent, the drum should be polished w ith fine em ery
clo th b u t should n o t be tu rn ed . A t this stage, elim inating all
grooves in drum and sm oothing th e ridges on lining w ould
necessitate removal o f to o m uch m etal and lining, while if left
alone, the grooves an d ridges m atch and satisfactory service
can be o btained.
I f drum is to be refinished fo r use w ith sta n d ard size brake
facings w hich are w orn very little , only enough m etal should
be rem oved to obtain a true sm ooth braking surface.
A brake drum m ust n o t be refinished m ore than .060” over
th e m axim um standard diam eter, rem oval o f m ore m etal will
effec t dissipation o f heat.
Out-Of-Round or Tapered Drum
A drum th a t is m ore th a n .006 out-of-round on the
diam eter will result in rough brake application and should be
refinished. O ut-of-round and th e diam eter can only be accu­
rately m easured w ith an inside m icrom eter fitte d w ith proper
extension rods.
An o ut-of-round drum m akes accurate brake shoe adjust­
m en t im possible and is likely to cause excessive wear o f other
p arts o f brake m echanism due to its eccentric action. An
out-of-round drum can also cause severe and irregular tire
trea d w ear as well as a pulsating brake pedal. When the braking
surface o f a brake drum exceeds th e fac to ry specification
lim its in taper (a n d /o r) being o u t-of-round, th e drum should
be tu rn e d to true up th e braking surface. O ut-of-round as well
as taper and w ear can be accurately m easured w ith an inside
m icrom eter fitte d w ith p ro p er extension rods.
When m easuring a drum fo r o u t-of-round, taper and w ear,
take m easurem ents a t th e o pen and closed edges o f m achined
surface an d at right angles to each other.
Micrometer Method (Fig. 29)
1. Place the brake drum on a sm o o th surface.
2. Using m icrom eters, place the tips at the center o f the
drum face.
3. While sweeping ho rizo n tally and vertically, slowly adjust
the m icrom eter u n til m axim um c o n tac t is m ade. R ecord
this reading.
4. R o tate th e drum 45 degrees and repeat Step 3. C ontinue
until 4 readings have been m ade. The difference betw een
these 4 readings m ust not exceed .006.
Cleaning
New brake drum s in parts stock are given a light coating o f
rust proofing oil to prevent th e form ation o f rust on the
critical braking surfaces during th e tim e th at th e drum s are in
storage.
Fig. 2 9 —M easuring D ru m fo r O u t-o f-R o u n d
This rust proofing oil m ust be carefully rem oved before the
drum is placed in service to prevent any o f this oil fro m getting
on the brake shoe facings.
It is recom m ended th a t a suitable volatile, non-toxic,
greaseless type solvent be used to clean the oil from the
braking surface o f the new brake drum s before they are placed
in service to insure the cleanest possible surface.
G asoline or kerosene should n o t be used as there is danger
th a t a p o rtio n o f the d ilu ted oil substance m ay be left on the
braking surface.
N O T E : A ll brake drums have a maximum diameter
cast into th em . This diameter is the m axim um wear
diameter and n ot a refinish diameter. Do not re­
finish a brake drum th at w ill not meet the specifica­
tions as shown below after refinishing.
(REPLACEM ENT)
O R IG IN A L MAXIMUM R EFIN ISH (DISCARD)
DIA M ETER D IA M ETER DIAM ETER
11.000 11.060 11.090
12.000 12.060 12.090
13.000 13.060 13.090
SHOES A N D L IN IN G S —FRONT DISC BRAKES
The brake linings should be inspected any tim e th at the
wheels are rem oved. Check b o th ends o f the o u tb o a rd shoe by
looking in at each end o f th e caliper. This is the poin t at which
the highest rate o f wear norm ally occurs. A t the same tim e,
check the lining thickness on the inb o ard shoe by looking
dow n through the inspection hole in th e to p o f the c a lip e r-se e
“ Brake In sp ec tio n .”
The o u tb o a rd shoes have ears near th e o u te r edge w hich are
b e n t over at right angles to the shoe. The top ends o f the shoe
have looped ears w ith holes in them w hich the caliper retaining
bolts fit through. The large tab at the b o tto m o f the shoe is
b e n t over at a right angle and fits in th e cut-out in the
o u tb o a rd section o f th e caliper (Fig. 30).
C H E V Y V A N S H O P M A N U A L