A sudden locking of the rear axle while driving is one of the most dangerous defects that can occur in a vehicle. The reason for this is that, in most cases, the vehicle swerves, and it is only with great driving skill that the vehicle can be controlled again.
Nothing turns anymore
In our example, the defect occurred during parking. The left rear wheel locked after a clearly audible cracking sound while reversing. For the auto repair shop, the main question now is how the brake drum – the vehicle in question is equipped with drum brakes – can be disassembled without destroying other parts.
Tips and tricks
In the following, there are hints and tips as well as a short explanation of the different adjustment devices and how to reset them to make it easier to disassemble the drum.
How-to-guide
The system installed on the vehicle must first be identified. The part number of the brake-shoe set can be found in the product catalog by means of the vehicle data. The image that is then displayed for the part number provides the relevant information on how to use the adjustment device and how to proceed in order to release the brake.
In our case, the handbrake lever had to be moved through the threaded holes of the wheel bolts with a punch towards the anchor plate. The handbrake stop (bump at the lever) then springs behind the brake shoe and therefore exposes the so-called incremental adjuster. To do this, the drum must be turned to a position that allows attaching the punch right at the lever.
To ensure that the lever fully springs back, it may be necessary to completely detach the handbrake cable.
Now the drum can be disassembled. In this case, the cause for the brake locking up was a lining (brake shoe's friction material) that had become detached. After mounting a TRW Superkit and adjusting the handbrake, the error was eliminated.
There are additional adjustment systems below and information on how to reset them.
Bosch/Bendix – Long Lever Adjustment
a) Press both levers apart in the direction of the arrow, thereby separating the gearings.
b) Lever springs back and exposes the brake.
Bosch/Bendix – Short Lever Adjustment
a) Press the lower lever in the direction of the arrow, thereby separating the gearings.
b) Upper lever springs back and exposes the brake.
VW Wedge Adjustment
a) Press wedge in the direction of the arrow.
b) As a result, the shortened adjustment mechanism exposes the brake.
Lucas – One Shot Adjustment
a) Press both pinion segments apart in the direction of the arrow, thereby separating the gearings.
b) As a result, the shortened adjustment mechanism exposes the brake.
Note
Only some of the systems are described here due to the large number of adjustment devices. In general, all drum brake systems have a mechanical adjustment unit that can be reset accordingly.
ZF Aftermarket product range
Discover the complete portfolio of brakes in our product catalog.
