BMW Handbrake (Originally published in the BMWCC magazine)

[Mike Fishwick]

BMW Brake Maintenance Part 4 – The Handbrake Mike Fishwick

(Originally published in the BMW Car Club magazine)

The BMW handbrake employs drum brakes integral with the rear discs, which obviously have to be removed if access is required. This can be less than easy, and is the basis for the increased price of an Inspection 2, which on most BMWs is little different from an Inspection 1 apart from requiring that the condition of the handbrake shoes is inspected.

It is basically a simple task, and well within the capabilities of a reasonably practical owner, but the problems which can be encountered on neglected older models mean that if the handbrake operates well, or can be adjusted to do so, the hidden mechanism is often ignored.

However, once you have overcome the often-rusted caliper carrier and disc bolts, the handbrake shoes will soon be visible.

You may experience problems in removing the rear discs when all the fasteners have been removed, but a few sharp blows with a hide-faced hammer around the rear of the disc will usually free it. Sometimes, however, the shoes may foul on a band of rust and solidified brake dust around the end of the drum area. It will therefore be necessary to slacken the adjusters until the shoes are clear of the obstruction, when the disc can be removed and the band of rust chipped away.

The shoe linings never wear out, but after many years – particularly in damp climates such as the UK – the linings can become detached from the shoes by corrosion, often jamming between the shoes and their pivots and being destroyed. In such cases it is possible for sufficient heat to be generated to damage the hub bearings and seals, and sometimes even the caliper seals.

It is therefore worthwhile to remove the drums every couple of years or so, looking for the crack-like lines between the linings and shoes which indicate progressive failure of the bonding. Should replacement of the shoes be necessary, they can then be levered out of their pivots and removed along with the adjuster.

This is a good opportunity to service the adjusters, after first measuring their overall length as a rough datum for reassembly. Unscrew the adjusters, clean them, and reassemble after lightly coating their threads with grease. After fitting the shoes turn the adjusters until the drum can just be fitted over the shoes, and reassemble.

Adjustment is a simple task, but one of the least-understood, due to the usual instruction to ‘rotate’ the adjusters. They resemble small gear wheels, and many hours are wasted attempting to lever them up or down with a large screwdriver against the edge of the wheel bolt hole.

This has confused generations of BMW maintainers, not to mention the authors of the Robert Bentley Z3 manual, who fail to realise that levering against the bolt hole reverses the direction of the screwdriver tip, when compared to the movement of its handle!

The trick is to use a long but narrow screwdriver (about a quarter of an inch wide) and to push against the upper or lower area of the adjuster wheel to cause rotation in the desired direction.
The direction is another problem, for the adjusters are of two-piece construction, joined by a right-hand thread. As the same adjuster is used on both sides, the apparent direction of adjustment to produce the same effect on either side of the car is different. If in doubt, point the threads of a bolt in the car’s direction of travel, screw a nut onto it, and imagine the nut to be the adjuster.

As you unscrew the nut the ‘brake’ will applied – you will soon appreciate the problem, for to apply the left handbrake the adjuster must be pushed at its top, or the bottom to be slacked off. The right-hand adjuster is pushed in opposite directions.

A common problem is that of setting the wheel in its correct position. Each of my discs therefore has a small notch filed into its edge, which when aligned with the top of the caliper carrier will line up the top wheel bolt hole with the adjuster. Pull the handbrake fully on and off a few times to centralise the shoes, and with the lever in the ‘off’ position use a screwdriver to push the adjuster in the appropriate direction to apply the brake. When the brake is providing serious opposition to turning the wheel, reverse the adjuster until the wheel is free.

When this operation has been carried out on both sides, remove the boot around the handbrake lever, and set the cable adjusters to give about three clicks of movement, at which point both wheels should be locked. Check that the handbrake warning lamp operates as the lever is pulled, and that when the handbrake is released it goes out, and the rear wheels rotate freely.

Apart from mentally checking the operation of the handbrake whenever it is used, and adjusting the brakes if necessary, all that is required is to occasionally apply it at 30 mph or so to keep the working surfaces of the linings and drums clean.

Being a single-leading shoe design – in order that it operates with equal effect in either direction – it has what to many new owners is an odd characteristic, in that when parked on a hill the car can sometimes move a little against the handbrake when the footbrake is released. This is simply because its full efficiency depends on the leading shoe ‘winding up’ to wrap its full lining area against the drum.

Given that it is in good condition and well-adjusted, this is one of the better handbrakes, and is far more reliable than most of those which operate via the rear discs. For example, they are proof against the problem experienced by some owners of the MINI or VW ranges, which are known for running away after being parked. The aluminium rear calipers used on these cars contract as they cool down, with the result that the handbrake eases off, a situation which is not helped by the requirement of the Driving Standards Agency that new drivers be taught to always leave the gearbox in neutral when parked – probably to make it easier for front-wheel-drive cars to be towed away backwards.

For example, I know of one BMW dealership where a MINI demonstrator had been left in neutral after being driven by two Approved Driving Instructors. While no-one was looking it decided to go for a drive – across the parking area, over a kerb, down a steep tree-covered slope, across a pavement, a busy road, another pavement, down another slope, and came to rest – without damage, a foot from the wall of a shop!