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GMC Great Lakers Motorhome Club!
6-Wheel Disk Brakes!
Page 1 of 9
6-Wheel Disk Brakes
Converting the stock brakes to Cadillac-based disk brakes
Complete instructions and part list follow these photos and figures
!"#$%&'$(#")
Photo 1
This is the backing plate to
which the caliper for the disk
brake attaches. Note the white
areas. These areas need to be
ground off to clear the swing
arm. This item is also painted
blue in most other pictures in
this document. The center hole
must be re-bored to 2.30" in
diameter. Remount it using
existing bolts. Do not grind all
backing plates the same, two
(if using four) backing plates
must be ground off the
opposite of how Fig. 1
indicates.
GMC Great Lakers Motorhome Club!
Photo 2
The image at right shows the
routing of the emergency brake
cable to the rear caliper. Note
the fabricated bracket where
the hard brake line and the flex
line meet. The backing plate
rock shield is removed and is
painted light blue in this photo.
This backing plate is shown
without the dust shield.
Photo 3
This is the return spring for the
rear caliper parking brake. It
must be installed for proper
return of the parking brake arm.
6-Wheel Disk Brakes!
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GMC Great Lakers Motorhome Club!
Photo 4
This is a disk rotor from a
1976-1978 Cadillac Eldorado.
For template on hole
configuration, see Fig. 2.
6-Wheel Disk Brakes!
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GMC Great Lakers Motorhome Club!
Photo 5
The parking brake cable spring
arms (red) must be trimmed off
approximately 1/16" to be
capable of expanding once
inserted through the backing
plate.
Add a 1/2" x 1 1/2"compression
spring to the existing return
spring using a discarded "nail
cap". Enlarge the center hole of
the "nail cap" to accommodate
the parking brake cable then
split it half way to go over the
cable.
Photo 6
Using '76 to '78 Cadillac
Eldorado rotors, centers rebored to 3 7/8" and chamfered
to fit hubs. Using one original
bolt hole re-drill three new bolt
holes to 5" on center. Re-bolt to
hub using four (4) original bolts.
This photo shows backing plate
with dust shield.
6-Wheel Disk Brakes!
Page 4 of 9
GMC Great Lakers Motorhome Club!
Photo 8
This is the same as the
previous picture but the backing
plate does not have the dust
shield.
Photo 9
Use 20' brake lines and bend to
fit. Repack rear wheel bearings
(or replace). Torque to GM
specifications (see maintenance
manual). All parts needed to do
the job are listed on the pages
that follow.
6-Wheel Disk Brakes!
Page 5 of 9
GMC Great Lakers Motorhome Club!
6-Wheel Disk Brakes!
Page 6 of 9
FRONT PROCEDURE
1. Remove MASTER CYLINDER
2. Remove BRAKE BOOSTER
3. Replace BRAKE BOOSTER with SENSITIZED BOOSTER
4. Install new P30 MASTER CYLINDER (Auto Zone # 10-1668) (PROPORTIONAL)
5. Remove PROPORTIONING VALVE, off frame and splice lines
5.1.
Front to Front.
5.2.
Rear to Rear.
5.3.
(Replace all brake lines if original)
6. Remove Front Wheels
7. Remove Rubber Brake Hoses
8. Remove Front Calipers (SAVE)
9. Reinstall new 80 MM Calipers (Grind off all flashing so caliper will fit)
10. Install new Brake Hoses using METRIC BANJO bolts.
11. Bleed Front Brakes
REAR PROCEDURE [CENTER WHEEL]
1. Remove Wheels
2. Remove Drum, Brake Shoes, and Parts and Emergency Brake Cable and Backing Plate
3. Remove Hub from Drum (8 Bolts) SAVE BOLTS.
4. Reinstall Eldorado Backing Plates – Use same grade bolts (Center hole RE-BORED to 2.30” Dia.
and outside edge chamfered. (Grind both parking brake entrance holes to fit on Bogie.)
(Fig. 1)
5. Bolt Rotor to Hub, using 4 bolts (Rotor Re-bored to 5” Center to Center Bolt Pattern and Center
Hole re-bored to 3 7/8 “ chamfered to fit hub. (Fig. 2)
6. Reinstall ROTOR/HUB (good time to re-pack and/or install new bearings and races.
7. Install CALIPER from Front Wheel (caliber facing forward.)
8. Connect Brake Hose to Caliper (drill center of hose fitting to 7/16 “ for banjo bolt.)
9. Mount new hose bracket to rear bolt on hub and connect Brake line.
GMC Great Lakers Motorhome Club!
6-Wheel Disk Brakes!
Page 7 of 9
REAR PROCEDURE [REAR WHEEL]
1. Remove Wheels
2. Remove Drum, Brake Shoes, and Parts and Emergency Brake Cable and Backing Plate
3. Remove Hub from Drum (8 Bolts) SAVE BOLTS.
4. Reinstall ELDORADO Backing Plates – Use same grade bolts (Center hole RE-BORED to 2.30”
to fit on Bogie.) (Fig. 1)
5. Bolt Rotor to Hub, using 4 bolts (Rotor Re-bored to 5” Center to Center Bolt Pattern and Center
Hole re-bored to 3 7/8 “ chamfered to fit hub. (Fig. 2)
6. Reinstall ROTOR/HUB (good time to re-pack and/or install new bearings and races.
7. Install PARKING BRAKE CALIPER
8. Install PARKING BRAKE CABLE to CALIPER. (Add compression spring (1/2”) to section of cable
existing spring doesnʼt cover. Use nail cap from discarded parts
9. Connect Brake Hose to Caliper (drill center of hose fitting to 7/16 “ for banjo bolt.)
10. Mount new hose bracket to rear bolt on hub and connect Brake line.
Gravity bleed all brake lines. To bleed Rear Calipers, Remove and Rotate so Bleeder is on Top.
Reinstall when complete
IF BRAKE PEDAL IS LOW – REPEAT PROCEDURE
11. Connect Parking Brake Cable to existing Parking Brake Cable from front of Coach.
6-Wheel Disk Brakes!
GMC Great Lakers Motorhome Club!
Page 8 of 9
PARTS LIST
FRONT WHEELS
1 - MASTER CYCLINDER"
34 MM P30"
AUTOZONE"
1 - VACUUM BOOSTER"
"
LEIGH HARRISON
1 - 80 MM CALIPERS"
"
AUTOZONE"
L90185
1 - 80 MM CALIPERS"
"
AUTOZONE"
R90184
1 Set - BRAKE PADS"
"
AUTOZONE"
1534
1 - BRAKE HOSE"
"
AUTOZONE"
L77320
1 - BRAKE HOSE"
"
AUTOZONE"
R77421
313940
2 - BANJO BOLTS"
"
AUTOZONE"
4 - CALIPER BOLTS"
"
AUTOZONE
1 - CALIPER HARDWARE KIT"
"
10-1668
AUTOZONE
REAR WHEELS
4 - BACKING PLATES"
ʻ72 – ʼ76 CADILLAC ELDORADO " SALVAGE YARD
2 - CALIPERS"
"
W/BUILT-IN PARKING BRAKE"
(Need to be Rebuilt)
SALVAGE YARD
4 - ROTORS (ʼ72 – ʼ76 Cadillac Eldorado) USED To be turned"
"
NEW"
SALVAGE Yard
J. C. WHITNEY"
8ST56819N
4 - BRAKE HOSES"
AUTOZONE"
77226
"
2 - BANJO BOLTS"
"
AUTOZONE"
313940
4 - HOSE BRACKET CLIPS"
"
AUTOZONE"
1457
2 - BRAKE HOSES"
"
AUTOZONE"
L10098278
2 - BRAKE HOSES"
"
AUTOZONE"
R10098279
2 - SETS OF BRAKE PAD"
"
AUTOZONE
8 - CALIPER BOLTS"
"
AUTOZONE
1 - CALIPER HARDWARE KITS"
"
AUTOZONE
1 - GALLON BRAKE FLUID
GMC Great Lakers Motorhome Club!
6-Wheel Disk Brakes!
1 -" Machine work for inside of Backer Plates enlarge to 2.300” and chamfer Axle side.
Inside bore of rotors enlarge to 3.880” and chamfer Hub side.
Drill 31/2" holes in rotors on 5 “ center 900 apart.
2 -" Nail Caps reused from removed Brake Shoes, Drill center larger and split one side.
2 1/2" x 3 “ Compression Springs for Emergency Brake cable.
2 -" 1” x 1” x 2” angle iron Brake Hose Bracket, fabricate to fit, Drill each side.
2 -" Emergency Rear Brake Cable (Use longest one from removed set).
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