Columbia ParCar Expediter EX21-24A, Service Manual

Page: 36 / 94

Section 5 - Accelerator & Brake System
BRAKE DRUM SERVICE 1.
Rebore or replace
drum:
if rubbing surface is rough or ragged, or if depth of scoring
exceeds .010”.
if inside diameter of drum at open end exceeds inside diameter
at closed end by more than .010”. if surface variance exceeds
.005” on the side.
if hard spots cause noticeable effects such as pedal pulsations
or brake roughness. if spots are severe, replace drum.
if heat checking is plainly visible or can be felt with a
fingernail.
If checks are severe, replace drum.
if out-of-round condition
exceeds .006” total indicator
reading or if pedal pulsations or brake roughness is
noticeable.
2 To measure a drum diameter, place gauge in drum so contact
points are at greatest diameter. Be careful to hold both
contact points at same depth (distance from outside edge
of drum).
3.
Rebore limit is .060” over original drum diameter.
4. Difference in diameter of drums on opposite ends of the
same axle must not exceed .010”, or when turning drums
turn them in pairs to same oversize (within .010”) to
ensure equal braking effort on all wheels.
Never rebore a drum to maximum wear or discard
diameter.
5. When reboring a drum, remove only enough metal to
obtain a smooth braking surface. If drum does not clean
up when turned to maximum rebore diameter, replace it.
Removal of more metal will affect ability of drum to
dissipate heat and may cause drum distortion.
REASSEMBLY
1. Apply a small amount of white lithium grease to the
threads of automatic adjuster screw and to contact points
where brake shoes rest against back plate.
2. Install automatic adjuster screw and nut into automatic
adjuster assembly. Reconnect top and bottom shoe return
springs to brake shoes in same order as removed.
Brake shoes may not be equal in length. The shoe with the
shorter lining should be installed on the brake assembly
side closest to the front of the vehicle. Shoe with longer
lining installs to the rear.
3. See Figure 5-2. With the springs attached to the brake
shoes, hook bottom of each brake shoe, one at a time,
into slots on automatic adjuster screw and opposing
retainer. Next, hook top end of each brake shoe behind
anchor at the top of brake plate. Fold ends of shoes
inward towards brake plate. Secure them in place with
brake shoe pins, retainer springs and 1/4 turn fasteners.
4. Install auto adjuster spring. Using a fl at blade
screwdriver, turn the adjuster nut away from the backing
plate. Check to make sure the shoes are spreading further
apart. Make sure the brake drum still slides on easily.
5. Install the brake drum 3/4 over the brake assembly and
using a brake spoon or brake adjusting tool, rotate the
brake adjuster until drag is felt against the brake drum.
Push the drum fully onto the assembly.
6. Apply pressure to the brake pedal and release, then
check to see if additional adjustment is required to create
drag on the drums.
7. When adequate drag is achieved (very slight drag), install
wheel hub and drum fully onto brake assembly. Engage
brake and install a new axle nut. Tighten axle nut to a
minimum 65 ft. lbs. (23 Nm) Install new cotter pin.
8. Reinstall rear wheel/tire assembly and four lug nuts.
Engage brake and tighten lug nuts in a criss-cross pattern
to a maximum 65-70 ft. lbs. (23-25 Nm) (Figure 5-3).
Repeat for other rear wheel. Recheck lug nut torque with
vehicle on the ground.
BRAKE STRIP REPLACEMENT
To perform this service, raise vehicle using floor jack
and safely support it with jack stands positioned under
main frame tubes. See Section 3 - Lifting Instructions.
1. At rear brake assembly (Figure 5-4), remove cotter pin
and clevis pin from brake strips at rear brake drum.
Discard cotter pin and e-ring.
Figure 5 - 3