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Brakes not so good. - timbigden@icloud.com - 31-03-2024
Morning all.
I’m working on my new to me 1933 PD to get it to a point that I’m confident to undertake longish drives.
Currently despite lots of work my brakes don’t inspire me, they work fine for light braking, but braking hardly improves as pedal pressure is increased. The brakes don’t pull significantly to either side, but I can’t lock any of the wheels. Being on four new longstones does mean plenty of grip.
So far I have:
Re-lined all shoes
Replaced rear cams, bushes and cotter pins as they were worn.
Bolted through the O/S cross shaft mounting as the rivets were loose.
As the front brakes have Bowden cables I have beefed up the Bowden outer anchor points on the drum backplates as they were moving under heavy pedal pressure.
Cables are in good condition and the inner and out cross shaft isn’t seized.
Drums look good and aren’t distorted.
I’d like to hear from any owners in south Suffolk who could give me a second option.
Any other suggestions very welcome.
RE: Brakes not so good. - Reckless Rat - 31-03-2024
A7 brakes are not like what you would expect on a modern, but properly set up they are "adequate". The degree of braking efficiency makes no difference whether you are tootling about round near to home or on a long run. Defensive driving techniques are necessary. Planning, anticipation and alertness count for more. No servo assistance also means that you have to press bloody hard on the pedal at times.
If it's any consolation, on my 33 RP (without Bowdenex conversion) fitted with Longstones on 19" rims like your PD, I have never, ever, been able to lock the front wheels except when playing about on a gravelly car park. You really don't want the rears to lock anyway because in extremis that will just cause the car to rotate.
It is important, however to ensure that the adjustment is correct and that cables and levers never go beyond 90° on full application.
RE: Brakes not so good. - "Slack Alice" Simon - 31-03-2024
My brakes ('34 Tourer) are barely adequate.
I, too, have replaced most things.
I though I had improved them, until my neighbour bought a Seven and asked my to drive it.
It stops almost like a modern!
When he isn't looking, I will take a wheel and drum off, and see what is on the shoes.
Very frustrating, though, to know it can be done.
In the meantime, I drive, as I always have, defensively.
Braking is much helped by engine braking, if you can co-ordinate it.
RE: Brakes not so good. - stuartu - 31-03-2024
Tim, you may find that there is not universal enthusiasm for Bowdenex. My experience is that, properly arranged, they work very well.
I notice in one of your earlier posts that your reversing hiccups seemed greater on lock.
It is commonplace to find that the unmodified geometry of the standard braking system can induce problems but this should not be the case with Bowdenex - unless the cables are dragging.
Because most Bowdenex cables I have seen have grease nipples, people tend to grease them. This usually results in cable drag, particularly after a few years of the grease hardening.
My first move on reconditioning existing Bowdenex is to suspend the cable by an extremity and play a hot air gun over its length. Put down a tray to catch the dripping! Keep at it until the cable returns freely with just its own spring pressure.
I would lubricate with oil, circa sae 10, no thicker. Motor cycle fork oil, perhaps?
Once the cables are moving freely this should enable you to adjust the front brake shoes closer to the drum without inducing drag or snatch. A few thou at the drum makes quite a difference at the pedal.
It is also worth checking which rear brake levers are fitted. Bowdenex levers are longer than the early levers. If your car has early rear levers and the rear brakes are adjusted up fully they will inhibit full movement of the front levers for obvious geometric reasons.
Hope this helps.
Regards,
Stuart
RE: Brakes not so good. - AustinWood - 31-03-2024
If the brake linings are hard the brakes won't work well.
We have Green Gripper brake linings from Saftek. They are excellent. Saftek are impressively efficient too.
In the past I had a car with Bowden cables at the front. I could never get them to work. There was too much friction in the cables. If they are old or have been greased they will never work properly. They should be cleaned thoroughly and then oiled.
The front to back compensation is poor on the coupled brakes. The fronts should be set up to come on before the rears.
Our car is 1929 so the footbrake works on the back wheels only and the hand brake is fronts only. The back wheels lock easily, the fronts don't, but do pull up very well.
RE: Brakes not so good. - Ivor Hawkins - 31-03-2024
I wouldn’t knock Bowdenex cables, but in my experience, I haven’t been able to gain any advantage over the standard set up, so I removed the cables and went back to standard.
As Rekkers said, the standard set up is “adequate” on standard brake shoes, so I drive the seven like I ride a motor cycle, looking ahead, braking early etc.
But, on a more positive note I had green gripper linings on my special and that would stop like a modern!
Edit: I’ve just spotted the axle tramp thread and as may have been spotted, sticking Bowdenex cable won’t help with that, so the old hot air gun treatment will certainly help there too!
RE: Brakes not so good. - Malcolm Parker - 31-03-2024
If you have renewed everything it does not surprise me that the brakes do not inspire confidence. It takes time for the linings to bed onto the brake drums. With new linings only a fraction of the surface will actually be making contact with the drum. Likewise the bushes for the cams etc all need to get bedded in. They need to be loose and free without being excessively worn. Any friction in the wrong place is a bad thing with the cable set-up. I would drive the car for a month or two then check the brakes over and adjust as necessary. I live in a very hilly area and the brakes on my car are about ten years old. They work quite well by Austin 7 standards because everything is bedded in. I am sure that if I relined the shoes they wouldn't work half as well. When you get used to driving the Seven you will find that you can cover long distances with only the occasional use of the brakes. As Reckers has said, it is all about anticipation. If you have only a small engine, you need to maintain your speed if at all possible. It is however reassuring to know that you can stop if you need to!
I find that the brakes are okay for checking your speed but if you need to come to a complete stop it is the last few yards that seem to be the hardest!
RE: Brakes not so good. - John Cornforth - 31-03-2024
Hi
I think you are expecting a bit much to lock a wheel on dry tarmac unless you have a lightweight early car or special. In my experience, Austin brakes manage a squeak over 50% "efficiency" and the later Semi-Girling ones maybe 65% if well set up - and this is when applying as much pedal pressure as you can muster. I have a sneaky feeling that the 50% MOT pass threshold introduced in 1960 (and still the same !) was set especially for A7s.
There are really only two advantages to Bowdenex. One is that they overcome the "anti-servo" effect of twist in the early front axle, which worsens braking when going forwards and improves it when reversing (not very helpful). The other is that the effect of steering on braking is eliminated. The disadvantage is that they introduce friction, which is not present in open cables.
Before the semi-girling cross shaft came along in mid 1936, there was no compensation between front and rear brakes apart from the effect of a little bit of springiness in the cables. This means that the fore/aft adjustment is critical, a few turns on the adjustment nut (on the front brake linkage) can have a big effect on the front/rear balance. Unfortunately, the total braking effort tends to remain constant.
I second the advice to use modern soft linings, but it is important that they are well bedded in to the drums. This can take a considerable time for a low mileage car, unless you speed up the process by taking the drums off after a short period of use and then sanding down any high spots.
RE: Brakes not so good. - timbigden@icloud.com - 31-03-2024
The new linings came from A7 workshop, not sure what brand but they are a lot softer than the linings I removed!
RE: Brakes not so good. - Tony Griffiths - 31-03-2024
Getting the lining bedded in is essential. A chap I know with a 6-inch brake car built as a replica of a 1923 Works racer had the inside of this new drums lightly bead blasted. After just a few applications there was near to 100% bedding and the brakes were very effective - though, of course, it is a very light car.