I have recently observed several Thunderbirds with what I will call "maintenance
malpractices" used on the brake systems. These practices occurred during brake
shoe or wheel cylinder changes. The 1955/56 models have the same brakes. The
1957 models have the same type brakes but the front shoes and drums are wider.
Some of the discrepancies observed are primary shoe in the wrong position,
Primary shoe retract spring not connected in accordance with shop manual
instructions, bonded and riveted shoes installed together on the same wheel and
mismatched wheel cylinders.
I highly recommend following the shop manual for each year when servicing brakes
and pay particular attention to the following items. Each drum has a primary and
secondary shoe. The primary shoe lining is shorter and should be on the front
for all four drums. The secondary shoe has a longer lining and should be on the
rear for all four drums.
- The primary shoe retract spring should be installed first. The secondary
return spring over laps the primary retracts spring.
- Brake shoes function better if they match within individual drums either all
riveted or all bonded.
- 1957 front brakes have a third retract spring approximately 7.5" long it
connects in the lower hole for the retract springs and passes below the wheel
cylinder. All 1957 early and late models originally had this spring.
- Both rear shoes have a parking brake lever attached to the inside of the
secondary shoe. The parking brake cable connects to the levers. They also
have a parking brake link that passes under the wheel cylinder connecting
the secondary shoe to the primary shoe.
- Wheel cylinders should match from side to side, same brand name if possible.
Mismatched wheel cylinders may cause uneven braking due to different size
internal fluid passages and openings.
- Brake drums should be machine turned to insure they are not out of round. This
also applies to new drums. Some of the new off shore drums have been found to be
out of round but in most cases they can be machine turned to within limits.
- The backing plates have six flat areas for the side of the shoes to slide on;
the worn surfaces must be removed and lubricated to prevent shoe hang-up. See
the Restoration Manual page 294 and 295.