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Adjusting your overrun braking system

Adjusting your overrun braking system

Overrun brake systems are fitted to all trailers in the UK that are rated above 750kg weight capacity. It is vital to your own safety, and that of other road users, that your braking system is correctly adjusted and your trailer can stop properly when required.

The adjustment sequence always follows the same pattern, starting with the brake drum, then moving on to the compensator and finally, the brake rod.

Before starting the adjustment ensure that the handbrake is fully off, and the trailer coupling drawtube is fully extended. The adjustment should ideally be carried out on level ground and disconnected from the towing vehicle.

Trailer Brake Drum

In the trailer brake drum, adjust the linings so that resistance can be felt when rotating the drum forwards. Always rotate the drum forwards rather than backwards to prevent the auto reverse mechanism kicking in which will prevent accurate adjustment. Repeat this on all brake units on the trailer.

If an over centre handbrake is fitted remove any locking pins and untie the lever. Apply the brake to ensure the brake shoes are correctly aligned. Once you’re satisfied this is the case refit the locking pins.


Ensure it is clean from grease and dirt with a dry cloth. Tighten the inner cable to get rid of any excess slack but ensure it’s not taut. Tighten all nuts sufficiently and add fresh grease.

Brake Rod

To provide the correct support the brake rod should pass through the centre of the anchor point by at least 50mm. Adjust it so that the overrun lever just touches the rear end of the draw tube shaft and tighten all locking nuts.

Once you have completed the adjustments it is wise to perform a road test to ensure that braking is effective at various speeds. Where possible, carry out these tests on private roads or roads free from other vehicles to avoid inconveniencing or possibly endangering other road users.

If you need any help in deciding which parts you need our TechTalk team are always on hand. Alternatively, you can look at our website that specialises in Trailer Parts.