Semi-Girling brakes

[falcott]

Hi there. Can anyone please tell me how to set up the braking system? In particular this fork-thing, which I'm told has to have an equal gap on either side of it. As you can see here, it is currently biased to the front of the vehicle. Many thanks.

[John Cornforth]

Hi

The square headed adjusters on each backplate are turned clockwise until the brakes lock, then back one or two "notches" (1/4 or 1/2 turn ) to establish the correct shoe to drum running clearance.

With substantial pressure on the footbrake, there should be about an equal gap between each side of the "fork-thing" and the pivot of the swinging lever. The swinging lever is a compensator which allows front to rear brake balance, so must be free to perform this function. The fork is only supposed to touch the pivot when the handbrake is in use, or as a fail-safe if a cable broke or was grossly out of adjustment.

Once the cables are set up, they should not need readjustment for a long time. Any brake shoe wear is accommodated by the adjusters on the backplates.

Purely out of interest, the various lever lengths in the cross shaft are such that the cable tension is approximately 60% to the front and 40% to the rear. This was an improvement over the earlier 50:50, and makes rear lockup less likely under heavy braking on wet roads.

[falcott]

Thanks. I've rebuilt the front brakes with new cams, levers and brake shoes. Then I had to have a longer front cable made because the brake levers are so far forward compared with the rearward bias of the old cams and levers. Two clicks of the adjusters from the "zero" position lock the brakes on, with the new brake levers are sitting at 45 degrees towards the front of the car. So I'm kind of wondering if everything that I've done is okay.

[John Cornforth]

Hi

There isn't really a "zero position" for the adjusters, the square headed bolts can wind out by many turns. However, you may reach a point where the hardened steel plungers in the adjuster touch each other at the nearest tips of their angled faces, so the shoes cannot retract any further from the drums. I guess this could happen if the shoes have been fitted with liings that are a little thicker than standard. As long as the brakes aren't binding this shouldn't be a problem, and in any case the clearance will increase as the shoes bed in.

Due to the fitment of adjusters in the semi-girling design, the position of the actuator cams and levers is more closely controlled than in the earlier design. It needs to be, because the cams are smaller to give more leverage and the levers are longer. When the brakes are fully applied the levers should ideally be vertical if you are to get maximum effectiveness, but as long as they are no further back than about 20 degrees I wouldn't worry. From memory, after adjustment the "off" position is usually about 10 to 20 degrees forward of vertical, so your 45 degrees does sound a bit large. Where do your levers sit with the brakes full off and full on ?

[falcott]

Thanks John.
I'm familiar with the Girling system, since I've run small sidevalve Fords for decades, and built a couple of Specials from them. What I'm trying to get my head around is the Austin idiosyncrasies.
The adjusters are wound right out, and there are only a couple of clicks until the brakes bind. The brake shoes have been relined with bonded material, so they may be slightly too thick. I supplied the drums when I had them relined.
The levers move approx 1/3 or 1/2 inch before the brakes are fully on, so they are still at about 40 degrees from vertical. I'm going to take it for a drive to see how they go. Or stop.
Otherwise I may have to get the linings reground for greater clearance.
The thing is, which I'm trying to get my head around, I replaced the cams and levers, and the cotter pin slots were in completely different places. The original cams had slots which aligned the levers in a rearward position, which is why I replaced them. I've had to get a new front cable made because I couldn't get the adjustment from the (shorter) original one.

[Tony Press]

You should always check new cams against originals- we have had some that were not correct 

[John Cornforth]

Hi

I think the angle on a cotter pin is about 15 degrees, so if you can get it to fit the other way round that will alter the lever angle by 30 degrees, hopefully in the direction you want.

[Malcolm Parker]

Girling backplates were not always fitted so that the levers were at the bottom.   On rear axles the backplate could be fixed such that the levers are very different.  It can be very confusing!  Many new levers have been made in the past with the cotter at the incorrect angle.  Whether the cotter is fitted from the front or the rear also affects the issue.  The strength of the lever return springs sometimes causes problems.  Good luck!

[falcott]

I bought the new front brake cams and levers from the Seven Workshop, because the old cams positioned the levers towards the back of the car. I placed a photo in my previous thread about brake hubs, which compared side by side the old cams with the new. The cams were remarkably different with regards to the cutout for the cotter. Basically nobody addressed the issue. One, or both, cams must be wrong.

The new cams put the levers at a point where the ball is almost touching the front edge of the backing plate. And I have the cotters positioned so as to bias the levers towards the rear of the vehicle.

I'm not sure that the originals are the actual *originals* because the car is a Special and it would have been rebuilt anyway. So I carried on with assembling everything, to the point where all I need to do now is to attach the wheels and take the car for a drive.

[Tony Press]

We try (not always successfully) to keep originals of Spare Parts to check reproductions for accuracy. 

Given the present suppliers are the only way to get parts it is important to have an experienced fitter to modify when necessary !