DESIGN ANALYSIS
of AC's post-war 2 Litre Saloon (page 5)
BRAKES
The type of brakes employed on the 2 Litre are of interest. The first system used was Girling's hydro-mechanical brakes, that is, hydraulic at the front and mechanical at the rear. The front brakes were the Girling "hydrastatic" system. The linings were in continuous contact with the drums to reduce pedal travel, and also make them self-adjusting. The rear brakes featured a compensating unit mounted on the rear axle to keep the two rear brakes in balance.
The pedal operates via a balance linkage to distribute the force between the mechanical brake-rod and the master-cylinder. The handbrake operates through the same brake-rod. It is a push-pull type handbrake control which achieves the required leverage via a cable to the front of the car, and a large lever visible in the engine compartment. The first time I saw it tested on a rolling road (for its MoT test), the car almost lept out of the garage!
Very large 12 inch (305mm) drums are fitted front and rear, and the deep wells of the wheels keep the drums exposed to the air-stream. Slow speed braking is very effective even by modern standards, with a stopping distance of about 31 feet (9.5m) from 30mph (48km/h). This could be attributed to the long wheelbase and low gravity centre, reducing weight transfer under braking. Also, the high pedal force required (up to 160lbs/700N) allows careful control on the limit of adhesion with plenty of 'feel'.
The braking system was changed a number of times during the 2 Litre's production life. The front brakes changed to twin leading shoes, with the self-adjusting idea being dropped. This made the brakes less heavy to operate. Eventually, the rear brakes became hydraulic and rear drums also varied in design and width.
