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Fuzz explains handbrakes

‘The advent of disc brakes brought the need for a new solution’

Fuzz explains how this tech keeps your classic stationary

Forms of preventing vehicles from moving when stationary have existed for many centuries and indeed, the earliest motor vehicle handbrakes were taken straight from their horse-drawn predecessors. These took the form of wooden blocks held against the rubber tyres, sometimes with a metal or canvas lining for a spot of increased coefficient of friction.

However, with motor vehicles being able to be parked without consideration of animal motive power, the need for greater holding power on hills and suchlike increased dramatically. At the same time, motor vehicle service brakes were also developing into powerful means of the retardation of greater masses, and so it made sense to use the materials and, sometimes, the same or complementary systems.

Many early vehicles featured drum brakes on the rear axle only, plus a transmission brake, the latter sometimes being of the external ‘clamp’ type, onto a drum behind the gearbox, or a more conventional and modern internal shoed drum brake.

There can be a few complications here, because the transmission brake was often operated by a foot pedal, this being more likely when it was of the more forgiving external clamp-type, with the wheel, aka service brakes, being operated via rods or cables by an external, ratcheted hand lever, in much the same way as many parking brakes today.

Clearly, this was not an ideal situation, because steering and braking at the same time could be something of an art, although, arguably and ideally, the two ought not to have been combined in ordinary circumstances, so the service brakes migrated to the foot pedal and gained braking to the front wheels as well.

Cable and rod brakes gave the opportunity for the parking brake to directly operate the same service system, such as on the Austin Seven, thus acting as a ratcheted, hand- operated service brake. However, the advent of hydraulicallyoperated service brakes meant that the parking system needed to retain its own separate mechanical linkage, and so things started to become rather more complex within the rear brake drums only, which now featured hydraulic pistons expanding the shoes onto the internal braking surface of the drum in normal use, with levers or wedges actuating them in parking mode.

This satisfactory system continues in some vehicles into the modern era, but the advent of disc brakes brought a need for a new solution.

Enter the mechanically-operated, separate disc parking brake system, as fitted to the likes of Jaguar Mk2s. These featured cable-operated clamping pads, similar to traditional bicycle ‘rim’ brakes, whereby the cable casing acted upon one pad and the cable itself on the other, thus drawing them together. A spring fitted in between to keep them apart and away from the disc when not in actual use.

These mechanical disc parking brakes required regular adjustment and were prone to failure, especially when the spring weakened and allowed the pads to wear away as they flopped against the disc when not applied. This led to the reappearance of internal drum brakes, now fitted within the centre part of the rear discs and mechanically- or electrically-operated.

Certain vehicles continued to use transmission handbrakes, notably Land Rovers, between 1947 and 2015 and other companies, such as Saab, often assigned the parking brake to the front wheels.