Hints and Tips - Even More on A7 Brakes

From: David Laver
Date: Tue, 15 Apr 1997
To: BRITISH-CARS-PRE-WAR
Subject: Austin 7 brakes

> With regard to A7
> brakes, I understand there are some cast back plate available to
> convert to hydraulics for around 150 for a car set. If my experiences
> as a passenger in a chummy this winter are anything to go by, I
> would be ordering a set!!!!

I've got some older steel plates but the same cylinder set with twin leading shoes at the front. As for the performance of Austin 7 brakes they are not all the same. Cable brakes can be made to work almost as well as hydraulics but there is a long list of problems and solutions :

Problem : pressed tin drums that flex each time and are likely to be cones not cylinders.
Solution : late type cast drums freshly skimmed.

Problem : front axle twists under braking in the direction to take the brakes off - anti servo.
Solution : late type radius arms, new bushes, straps for extreme cases.

Problem : Cross shaft results in direct pull to offside rear, less pull to fronts, little pull to nearside rear.
Solution : For the rear brakes use front type brake cable mounted from centre of shaft.

Problem : too much effort to rear
Solution : as much slack to rear as to front (front slack necessary so brakes don't bind on full lock)
Solution : fix both ends of shaft and vary lever length on shaft (as I have currently)
Solution : let one end of cross shaft float and use long levers on front (stays in ballance)

Problem : adjustment by shims (every decade).
Solution : late type semi-girling back plates with adjuster.

Problem : wear at cam end of shoe
Solution : shim

There are a number of problems that hydraulics share with cable such as oil from the diff sneaking down the tubes (drill a drain hole and fit a lip seal).

Hydraulics suffer more from the damp - particularly if the car isn't used every day.

For the Lancia-Austin all the brake parts are new so it will start with silicone fluid but the cylinder are still prone to rust unless greased about as often as the Chummy brakes should be shimmed. Its a case of new problems for old but always problems.

David


From: David Cochrane
To: David Laver
Subject: Austin 7 brakes
Date: Tue, 15 Apr 1997

David,

Thanks for the tips re cable brakes. I agree with your thoughts re cable brakes, ie try to keep them if possible. A couple of comments:

Can the later type cast drums be fitted to vintage axles & 19 inch wheels?

Have you tried fitting early radius arms, boxed? BTW, make sure that the radius arm bolt is a tight fit in the ball on the chassis cross-member bracket.

If you use uncoupled brakes you get a simpler system, but you have to remember to grab the hand-brake all the time so that it is an automatic action in moments of excitement/stress.

Two ways to counter the cross-shaft problem:
1) Fit a cable bender in the right hand back brake cable to introduce some flex on that side to compensate for the flexing on the left side,
2) Fit a bolt from the left cross shaft bracket to the chassis cross member to brace it (you should see how that bracket moves...).

I know I'm a lazy sod, but even I think that adjusting the brakes once every ten years is reasonable...

Regards,
David Cochrane
(25 Chummy and a 28 Special one day...)


From: David Laver
Date: Tue, 15 Apr 1997
To: David Cochrane
Subject: Re: Austin 7 brakes

> Can the later type cast drums be fitted to vintage axles & 19 inch
> wheels?

There are a number of options, easy ones first :

o They improved the braking in 1932 with stronger drums and 1.25 in wide shoes. These parts fit with no modification.

o In Aug 36 they introduced the semi-girling setup. The cast drums fit the hubs but to fit the early wheels you will need to skim the outside. o To get the semi-girling adjusters at the front you need the later stub-axle, hubs, back plates etc etc. o For semi-girlings at the back you need to butcher two sets of axle casings to get the late outer on the early inner. Fitting a complete axle is hard work as they are wider . One way round this is to re-rivet the A frame with more splay and grind the spring mount on the axles.

David


From: David Cochrane
To: David Laver
Subject: Austin 7 brakes
Date: Wed, 16 Apr 1997

David,

1932/35 1.25 inch wide drums and shoes for the front brakes seems like a reasonably simple solution (I am a great believer in the KISS principle). I must look up the literature on modifying rear brakes, but bracing the n/s cross-tube bracket does make a helluva difference. My cousin has done it on his 1928 Top Hat and it makes the foot-brake feel far more solid.

I am afraid that having driven around with 6 inch brakes for the last 25 years, including several long trips on the continent, I tend to take a fairly relaxed view of the deficiencies in Austin Seven brakes. I found that driving a rear-wheel-only braked Edwardian was far more frightening. It is mainly a question of anticipation (and aiming for the gaps). Having said that, the Special will (hopefully) be going a lot faster, so I will pay more attention to its retardation.

Regards,
David C


From: david_cochrane
To: British-Cars-Pre-War
Date: Wed, 14 Oct 1998
Subject: Re: A7 Chummy (brakes)

Pete Bishop wrote:

> So far I only have the
> back brakes connected up but they seem OK. I am toying with what to
> do for the front brakes. Uncoupled seems to be the best for trials
> and coupled for road use. I am trying to think how I can have the
> best of both worlds - Dave Williams (Austineers) suggested leaving
> out the cotter pin that anchors the hand brake to the cross shaft for
> trials and refitting it for the road.

Pete,

The design of the Austin Seven brakes gradually lost the KISS principle as they developed, until the very end when they adopted the Girling system (when the brakes actually became effective for the first time). The vintage uncoupled system is pleasantly simple, about the only thing to be said in its favour. However, coupling the back and front brakes together didn't make them work any better, it just introduced complication. The cross-shaft tubes tend to seize up, and satisfactory adjustment is very difficult. I would advise keeping the brakes uncoupled, but you have to remember to grab the hand-brake all the time so that it is an automatic action in moments of excitement/stress.

Regards,
David C.


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