Semi-Girling brakes

[David Stepney]

The cables should be sufficiently taut so as not to cause the brakes to bind when the pedal and the handbrake are both off. The way I set the brakes is to then apply the handbrake two notches on and set the front brake cable so that the front brakes are just binding. Pull the handbrake on one further notch and set the rear brakes so that they are just binding equally. Any further adjustment can be done on the wing nuts on the handbrake and brake pedal. The brakes should be fully applied when the handbrake is pulled on four to five notches.

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Sorry, I forgot you have Semi Girling brakes. Adjust the brakes on the adjusters on the back plates and then set the cable tension as described in my previous post.

[John Cornforth]

Hi

For semi-girling brakes, disregard anything that applies to earlier systems. The front/rear compensator if working properly will automatically apportion the cable tension between front and rear when the brakes are being used reasonably hard.

Once set up in the factory, the adjustment sequence in service is:

Adjust shoe clearance with the backplate adjusters, they should be three quarter of a turn back from binding
If necessary due to cable stretch, equally adjust both the rear cable lengths to get equal clearance each side of the compensator fork with brakes on
Once set up, any subsequent lining wear is compensated for by using the backplate adjusters.

This information is paraphrased from "New Brakes on the Seven" published in The Austin Magazine, November 1936

There should be no more cable slack than necessary to maintain shoe clearance with the brakes off, so you may have to adjust the front cable length as well as the rear for a brand new setup. Note that there is no side to side compensation for the rear brakes, so check that the cables are equally taut with the brakes applied. If you like to be accurate, one way to do this is to firmly apply the handbrake, then pull the middle of each longest rear cable run sideways with a spring balance. Aim for equal deflections and read off the efforts required.

[Ruairidh Dunford]

Slacken off foot pedal butterfly (or hex) nut (and handbrake one, if fitted - is is possible to have Girling brakes fitted to an earlier system) completely.

Slacken off all cables and ensure the cross shaft is completely free and that the arms are lying towards the rear of the car.

Rotate all four square headed backplate adjusters up so the brakes are binding but rotating, using your hand, or the end of a hammer handle, operate the brake levers several times, this will help to settle and centre the shoes.

Adjust the square adjusters so that the hubs rotate freely.

Adjust the the front cable so that the front brakes are hard on with the pedal halfway down.

Adjust the rear passenger cable so that at half pedal it is binding (but rotates with effort) and the front brakes are still hard on.

Adjust the rear driver’s side cable so that it is scuffing and all of the above is still happening.

Finally take up any free play in the pedal with the butterfly/hex nut, and hand brake if applicable.

Once this is set you should only need to adjust the pedal free play and square backplate adjusters, until everything is worn out again.

[`Gordonhbm]

I had not appreciated that the semi girling brake shoes are self centring. How does the system work to achieve this please.
With the earlier, non girling brakes, there is no self centring of the shoes and this must inevitably lower their efficiency - anybody know by how much?

[John Cornforth]

Hi

The standard Girling arrangement with rollers and an expander wedge pulled by a rod has the actuator housing free to slide sideways (very slightly) to accommodate any mismatch in the shoes. The housing is fixed to the backplate with studs, thackray washers and castellated nuts with split pins. The backplate holes are slightly slotted and the nuts are not done up fully tight.

The Austin version with rotating cams has to have the actuator housing rigidly mounted on the backplate. The same washers and nuts etc are used (presumably because the cost of re-tooling wasn't justified) but the backplate holes are round and the nuts are done up tight.

As far as I can see, the shoes are free to float "up and down" but you could still get the situation where one was being activated slightly before the other. I suspect that in practice once there is some wear in the cam bushes and the more active shoe wears down a bit, everything more or less equalises itself.

[falcott]

Thanks for the help, everyone!

With regards to "self-centring", I've seen a video on yuotube which describes how to modify the Austin semi-girling system. Basically you cut off the upper part of the shoes, where they are notched for the adjuster, so they are straight. You cut off the notches, basically. That way they are free to slide up and down and centre themselves in the drum.