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The braking system is Hydro-mechanical, the front brakes are hydaulically operated and the rears mechanically operated. Both foot pedal and handbrake application apply the brakes on all four wheels, and is designed so that failure of either front or rear brakes does not put the pedal out of operation but allows one pair of brakes to be applied enabling the driver to make a safe stop. The supply tank situated on the steering column beneath the bonnet provides fluid to the master cylinder.


The master cylinder is connected to the pedal bisector lever by a rod and jaw end. When pressure is applied to the pedal the rod is pushed forward causing the plunger in the cylinder to exert presure on the fluid and operate the front brakes, the rear brakes being operated at the same time by the pull rod which is attached to the bottom end of the bisector lever, situated in the central compensator mechanism. The pull is transmitted to the rear brakes via realy levers and the compensator unit mounted on the rear axle casing, to which is connected the brake draw links from the rear brakes. Should a failure occur in the hydraulic sysytem the bottom end of the operating lever contacts the bisector level allowing the rear brakes to be applied. In the event of failure of the rear brakes, the upper end of the operating lever contacts the bisector lever, thereby allowing the front brakes to be applied.


The brakes are adjusted for lining wear at the brakes only and no attempt should be made to alter the operating linkage for this purpose. To adjust the front brakes, scotch the rear wheels, release the handbrake and slack off the hexagon adjusters (found diametrically opposed to each other on the backplate) by turning in an anti-clockwise direction. Then turn one of the adjusters in a clockwise direction until the shoe touches the drum, slack back until drum rotates freely and repeat for second adjuster.

To adjust the rear brakes, scotch the front wheels, release the handbrake, jack up the wheels clear of the ground and lock up the brakes in the drum by turning the squared adjuster wedge (protruding from the backplate in front of the axle) in a clockwise direction, slack back one or two clicks until drum rotates freely. Jack down and test.


This linkage is carefully adjusted and set by the manufacturers before leaving the works and should not normally require adjusting unless replacement parts have to be fitted or in the event of the system being overhauled. When carrying out this work the following instructions must be carefully followed:

GENERAL LAYOUT (Diagram 1 and Diagram 2)

The diagrammatic layout in Diagram 1 shows the operating linkage for right-hand steering A40 models, which differs somewhat from that shown in Diagram 2 for the left-hand steering A40. Before attempting to interfere with the adjustment on the vehicle, the appropriate diagram should be carefully studied in conjunction with the following notes.

Particular attention should be given to the points indicated on the diagrams and all dimensions quoted should be adhered to closely.

Diagram 2 also appertains to the A70 and A90 as the brake layout on these models is the same as for A40 L.H.D.

Diagram 1 - Right Hand Drive A40-A70-A90 Brake System

RHD Brake System (80K)

Diagram 2 - Left Hand Drive A40-A70-A90 Brake System

LHD Brake System (74K)

AUSTIN WORKS designed by Rob Stuart