uncoupled rear brake mods

[Malcolm Parker]

The standard front brake system does not bear too much scrutiny when the wheels are on full lock.   I believe Sir Herbert Austin took the view that no sensible driver would apply the front brakes on full lock!
I found that fitting strong return springs to the front brake levers stopped the brakes binding on full lock.

[Howard Wright]

Hi Gordon

May I ask if your desire to modify the brakes comes from experience of driving the car with the original set up?  

If so, then by all means apply the changes you are suggesting.

If not, I suggest you drive the car, asses and then make changes that you feel are needed.

For a road car IMHO the uncoupled Austin system is very adequate with one proviso, change the shoes and drums to 11/4”. Adjusting the rear brake cables to get both rear wheels braking evenly is not that difficult.

For a competition car then changes may be well worth it.

Cheers

Howard

[Robert Leigh]

I have seen an Austin 7 with a full pulley replacing the original curved track rocker at the centre, and I suspect that this may offer a marginal improvement. As for the ball ends of the levers not being on the king pin axes I think that if the cable can move fairly freely the tendency to tighten on one side will be offset by loosening of the other side, hopefully giving a similar pull on both sides.

[Steve kay]

I would very much agree that uncoupled brakes are perfectly satisfactory. However, the front brakes can bind when on full lock. This is most evident when the stops have been ground off to improve the turning circle if the car is much used for trialling or autotesting. Bowdenex brakes are helpful for such activities.

[Nick Lettington]

I have various old hydraulic brake backplates if you're interested in a hydraulic setup including unmodified 7" Morris Minor ones and a jig to set them up for welding (if you have time to modify them), a set already modified, you might possibly even persuade me to part with a full kit taken from a running vehicle that I was saving for a stalled project.

[`Gordonhbm]

Thanks for all the helpful replies.
Malcolm, totally agree with the principle of not braking heavily with the wheels on full lock! Your advice of fitting stronger return springs on  the front levers sounds excellent.  Not certain I understand the mechanics of why this works  - I  had assumed that the out of line ball was producing the mechanical force  so I can only assume  that the stronger spring ensures the compensator does its job.
Howard, desire comes from driving experience.  I hadn't thought of upping to 1 1/4" drums and shoes.    I wonder whether changing the pivot geometry of the non cam end of the shoes to  provide self-centering of  the shoes would be an advantage.
Nick, thanks for your kind offer but as already said I am going to stick to uncoupled brakes so won't be going down the hydraulic route.

[AustinWood]

The binding on full lock can be reduced by stopping and applying the handbrake briefly. This causes the front cable to readjust itself.

[Malcolm Parker]

There is always some slack in the front brake cable caused by the springiness of the cable where it goes around the compensating quadrant under the front cross-member.   If you try to remove the slack in the cable by adjusting it at the operating end, the brakes will most certainly bind when the wheels are on full lock.   The strong return springs effectively take out the slack from the cable by tackling the problem from the brake cam levers rather than the normal adjustment.  Hope that makes sense!
I think there is always a certain amount of play in the brake cams and levers and the return springs counteract this play.  The return springs need to be strong enough to take out the visible slack in the brake cable.   They also make the brakes firmer to operate which makes them feel more effective.

[`Gordonhbm]

Malcolm, thanks for that explanation - makes sense to me.

[Dave Mann]

One of the problems of the pre Girling brakes is that as the linings wear the movement of the brake lever increases until you reach a point where the springs in one hub brake are slightly stronger that in the other with the result that the latter can bind on full lock. My first Seven was hydraulic and I didn't appreciate the situation until I was helping a friend with a chummy who suffered the problem, try as we did we never resolved the problem. 20 years later in 1981 I acquired a cable braked RN and that's when I started to appreciate the problem. One of the first jobs I did was to replace the heavily worn brake shoe end caps with slightly thicker ones and coupled with new linings meant there was very little movement of the brake levers which hung almost under the king pins and the problem didn't arise. The car saw a lot of use and gradually the problem appeared which was resolved by fitting shims to the end of the brake shoes which returned the brake levers to their initial position. I have a bag full of these shims which are bent in a shallow U shape so they can't fall out and are easily changed. Another problem when I got the cable braked RN was that the replacement brake cams then available had a sharp corner which really chewed up the brake shoe end caps or shims. I soon realized that problem and put a nice radius on the cam corners.
I quite often see this problem on other owners cars where they complain that one of the brakes bind and I see one fully off and the other nearly on and a variety of springs on the brake levers.
Another item to prolong the life of the linings is to fit oversize brake shoe pivot pins and to have a selection of brake drums.