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6.8: Parallel Shoe Gap Adjustment
6.8.(a): For optimum lining wear distribution, brake shoes have controlled freedom to align with
the wheel contour as the linings wear.
6.8.(b): Each brake shoe holder pivots on its link arm. Its freedom to rotate under gravity is
controlled by a shoe holder friction mechanism.
6.8.(c): Spring loaded pins in each link arm bear against the inside of the shoe (Fig. 3). This
provides tension to maintain shoe alignment when the brake is released. The tension is not
adjustable. When a shoe is replaced make sure that both shoe alignment tension mechanisms
are re-installed.
6.8.(d): To align shoes with the wheel, apply the brake at the rated torque and make the
following initial adjustments:
6.8.(d).(i): Release the brake manually or under power.
6.8.(d).(ii): With the brake released, use a soft-faced mallet to tap the upper edge of each brake
shoe, in towards the wheel, in the direction it would rotate under gravity.
6.8.(d).(iii): Re-apply the brake, and the shoes will be forced to align with the wheel to optimize
parallel clearance with the wheel.
6.9: Time Delay Adjustment
6.9.(a): The actuator nameplate will indicate when optional time delay valves are installed.
6.9.(a).(i): Letter “S” indicates an adjustable piston retract, (brake application), time delay.
6.9.(a).(ii): Letter “H” indicates an adjustable piston extend, (brake release), time delay.
6.9.(a).(iii): If both letters “S” and “H” are present, then the actuator is equipped with adjustable
time delay valves independently controlling both the piston extend and retract times.
6.9.(a).(iv): When time delay valves are not fitted, the actuator response time to extend or
retract, is between 0.4 and 0.8 seconds depending on actuator size
6.10: With time delay valve(s) installed, the extend and/or retract times are adjustable between
approximately 0.5 and 10 seconds depending on actuator size.
6.10.(a): Remove the delay valve protective cap to expose the adjustment screw. For minimum
delay set the screw head flush with the housing. Fig. 1 shows valve location.
6.10.(a).(i): Turn the screw clockwise to increase, and counter clockwise to decrease the delay.
Note: The standard actuator has the shortest response time. An actuator fitted with delay(s)
provides longer response times, even when the delay(s) are adjusted for minimum effect.
8/17/2006 Page 20 of 33 MST/E Electric Shoe Brakes Manual
560022-R6