Tie Down TSB - Drum Brakes - Manual

Technical Service Bulletin
TIE DOWN ENGINEERING • 255 Villanova Drive SW • Atlanta, GA 30336
www.tiedown.com (404) 344-0000 Fax (404) 349-0401
Drum Brakes – Properly Adjusting Drum Brakes
Drum brakes for trailers sold by Tie Down Engineering and other axle suppliers are not self-adjusting. This
requires that the brakes are checked and adjusted on a regular basis.
The most important adjustment is at the time of delivery to the consumer. It is important to point out that
different brand and different size drum brakes may have adjusting wheels, or “star adjustors” that turn in
different directions to expand the brake shoes.
The Tie Down Engineering drum brake instructions state to “tighten the star adjuster while rotating the wheel
in a forward direction until the wheel reaches appoint where the brake shoes start to engage” as a first step.
The adjustment to set the brakes at a proper clearance state, “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 turns
with little effort.”
Many mechanics have been taught in the past to tighten the brake shoes until the wheel will not rotate and then
loosen the brake shoes by turning the star adjustor 10 or 12 clicks.
This can cause an issue with the brake operation.
1. “Clicks” may not be heard and the person adjusting the brakes could inadvertently loosen the
brakes excessively.
2. The brake-adjusting tool could grab the notched adjusting wheel in a position where more than one
“click” would take place at each adjustment.
3. The brake adjustment tool could slip, making a noise, but not moving the star adjustor.
4. Due to the above, brakes could be adjusted differently from left side to right side,
All of these “miss-adjustments” can create drum brake problems such as loss of braking power, brake chatter
at low speeds, uneven initial braking causing trailer sway and brake lock-up that damages the internal parts.
The second issue we would like to address is the assumption that the star adjustors turn the same way on all
drum brakes.
On TDE 10” and 12” hydraulic drum brakes, the star adjustors are mounted in the left and right backing plates
that allow a “pull down” on the brake tool to expand the shoes on the left or drivers side and a “push up” to
expand the shoes on the right or passenger side.
On TDE 7” drum brakes the star adjustors are set to allow a “pull down” action to expand the brake shoes on
both sides. Other manufacturer’s drum brakes can have similar or different “pull down” or push up” actions to
expand the brake shoes. The brakes may have been taken apart and the star adjuster installed opposite from
the original set up.
091710,C1143