Tie Down TSB - Drum Brakes - Manual (Page 2)

Technical Service Bulletin
TIE DOWN ENGINEERING • 255 Villanova Drive SW • Atlanta, GA 30336
www.tiedown.com (404) 344-0000 Fax (404) 349-0401
We purposely do not use the “push down” or pull up” of the brake adjusting tool in our brake instructions and
brake owners manuals due to the differences that can be found in brake drums.
Recent inspections of 7” drum brakes locking up on only one side of a trailer, has shown that the brake’s star
adjustors were in a very loose position, (star wheel in a collapsed position). This loose adjustment allows the wheel
cylinder piston to travel further than intended out of the cylinder bore when braking pressure is applied. The result
is that the brake shoes engage the hub and rotate slightly pulling the leading face of the piston downward wedging
the piston in the cylinder bore. The brake shoes are then locked-up because the piston is locked (wedged) in the
wheel cylinder. This condition does not happen with initial braking stops but will eventually occur if correct brake
shoe adjustment is not maintained. Once the brakes are “Locked-Up” they can only be corrected by disassembly
and replacement, the piston and cylinder are damaged. Unfortunately, the “Lock-Up” condition cannot be
corrected on the road by simply “backing up”.
This is why it is very important to follow the instructions on brake adjustment that is supplied with the brakes. If
you or your mechanic make an assumption that pushing up or down on the star adjustor expands or loosens the
brake shoes, you could inadvertently properly adjust one side and over loosen the opposite side brake.
Important:
1. FOLLOW THE MANUFACTURERS INSTRUCTIONS FOR ADJUSTING ALL DRUM BRAKES
2. NEVER USE THE “10 OR 12” CLICK METHOD TO DETERMINE THE PROPER ADJUSTEMENT POSITION
3. NEVER ASSUME THAT “PUSH UP” OR “PULL DOWN” EXPANDS OR LOOSENS BRAKE SHOES
4. ALWAYS START WITH A TIGHTENED BRAKE/WHEEL BEFORE STARTING THE LOOSENING OF THE BRAKE
SHOES TO GET A PROPER ADJUSTMENT
Below is the instructions supplied in the TDE Drum Brake Owner’s Manual
Initial Adjustment of Brakes (Applies to Both Electric & Hydraulic Brakes)
A. With trailer wheel off the ground and tire mounted. Remove the rubber access hole plugs from the rear of
the brake backing plate.
B. Inserting a brake spoon or flat screwdriver through the access hole(s), tighten the star adjuster while
rotating the wheel in the forward direction.
NOTE: Always spin wheel in the forward direction as if the trailer was traveling forward on the road.
Tighten the star adjuster until the wheel reaches a point where the brake shoes start to engage.
C. Loosen the star adjustor one click at a time while turning the wheel in a forward rotation. Continue
adjusting one click at a time until the wheel rotates with little effort.
D. Replace the rubber access hole plugs.
E. Repeat this procedure for all braking wheels.