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Hydraulics and cable brakes that work

Getting the best from cable brakes

If you want good brakes you don’t necessarily have to go down the hydraulic route if you’ve got no precedents to follow ie you’re totally starting from scratch. With modern high friction linings and everything set up right the standard cable brakes can be quite effective enough. There are further things you can do with cable brakes if you don’t mind moving away from ‘standard’. Some of these will be visible which could be a factor if you’re trying to stay ‘original’ but don’t forget that brakes are a safety feature. A subtle change that hardly anyone, only the real A7 anoraks, will notice but which does improve stopping power has to be a good idea?

 

The trick with standard brakes is not to compromise on quality or accuracy. Good quality high friction linings and accurate assembly/adjustment as they were designed to be. This includes no leaking hub seals or axles, the shoes well adjusted to the drums and cables/pedal rod well adjusted to the cross shaft.

 

It’s worth thinking about taking up any free movement between the shoes and the drums so the cables only have to move a short distance. I fit small steel plates with 2BA screws over the flat end of the Austin type shoe, there’s usually a groove worn in anyway. The other thing is that the linings are presented squarely to the drum. If the shoe is at a slight angle only the edge of the lining will touch the drum until you press the pedal harder with more force and cable movement. It’s hard to do anything in this way with the Austin shoes, try filing the flat brake cam face at an angle to compensate. Girlings can be adjusted by bending the centre ‘finger’.

 

To go further than standard you will need to start modifying. Remember the feeling when you stamp hard on the pedal, the back brakes lock up solid and don’t do much retardation and the front ones hardly come on at all? What’s needed is to have compensation, not financial compensation from Austin’s, brake compensation that is. A system that pulls all the brakes on evenly. Austin’s finally came up with some compensation with the introduction of the Semi Girling system in 1937. Like all things A7, it works reasonably well if it’s all OK.

Now the hard bit, you've got to build in a hand brake. It's tempting if already there, just to use the brake cross shaft and cables. However it weighs a ton and hangs down too far if you're wanting a low car. Also the lever sticks up and long way well forward in a low special. I would suggest all that is removed and an old style Mini handbrake mounted on or to the side of the tunnel, with a bit of ingenuity with the lever and ratchet you can mount it vertically like its predecessor. Place it where it’s reachable in an emergency but doesn’t get in the way of the gear lever or other things. Again it's got to be very solidly mounted. Run two cables (early Mini ones are long and have a threaded adjustable end) with pulley’s or outer cables to make them pull the quadrants on the rear brake cylinders. If you need to cut cables, silver solder the strands and cut through the middle with a Grinderette. Note that the pull has to be towards the differential not forwards for these hydraulic cylinder levers. The cable lever on the hand brake needs to be sized to give the right amount of pull at the back plate without excessive hand brake travel, 3 or 4 notches ideally to take up the slack and pull on the brakes.

 

Overall this isn't an easy job and unless your special 'should' have hydraulics or you've an engineering ambition to do the work, it's probably more worthwhile putting your time, money and effort into another part of the rebuild!

Other compensation systems have been designed over the years, Jack French in the Special Builders Guide showing how to do it. Another good read in general about brakes is Jack French’s two articles The Power to Arrest in the A7 Clubs Association 1981A & B editions.

 

The foot brake set up is usually fairly straight forward, getting a handbrake involved doubles the complication. You either have to get it to work on the same system but be able to work if any cable failed or you have to put in another set of cables to the rear brakes. Another thing to bear in mind with a redesigned system are the leverages exerted by the cross shaft and brake levers. Long levers exert a lot of force but need a lot of cable travel and vice versa with short levers. Cutting down on the free movement at the shoes as above cuts the amount of cable travel needed. There’s a balance to draw between cable movement to press the shoes onto the drums and the force creating friction between them.

It is difficult to use the Girling cross shaft on a low special, it does tend to hang down low, besides the handbrake lever is also usually too tall and too far forward.

 

Bowdenex brakes

These cables for the front brakes were a popular mod to improve braking. The idea behind these cables is sound but the normal 2” levers are sized to improve on the standard, pre Girling Austin brake lever lengths. If you’re fitting it to a Girling brake system watch out for the lever lengths. The normal Bowden lever is actually shorter than a Girling one—see the table below. Putting on 2” Bowdenex levers just reduces the ‘pull’ on the cam and you get even less retardation! If you want to go this way find some of the longer levers, preferably the really long 4” ones; see below.

 

There’s a few things that can be done to improve the Bowdenex set up. Invariably the two brackets for the front cross member have been whacked due to their low position. Make sure they’re mounted as high as you can get them, angle the cable up to them from the cross shaft and bend the brackets so they’re at 90 degrees to the cable run. These brackets also don’t seem to hold the outer cable very well. Drill out the hole to neatly fit the diameter of the end of the outer cable. Also trim off all excess length under the cable hole and radius the corners round. All this gives that extra little bit of ground clearance that could be vital on a low special.

 

Second hand Bowdenex kits usually are just the cables, make sure the anchors for the back of the cross member and back plates are there. If you’re lucky the front levers will be with the cables. If you’re extremely lucky the crossbar for the cross shaft lever will also be included. When fitting the Bowdenex don’t forget that an equal sized lever should be fitted to the back as the front if your system isn’t compensated. Front Bowdenex levers are cranked, rear ones are straight. The exception to this are the long 4” ones which should only be fitted to a compensated system and normal levers used on the back. If you haven’t got the correct crossbar or it’s bent (not unusual), they should be 1/2” mild steel bar 4” long with a 1/4” clearance hole parallel at each end. They tend not to want to sit evenly in the centre of the cross shaft lever. A small jubilee clip in the centre of the eye or one either side will keep the even balance.

The best Bowdenex set up is with a Girling or equivalent compensating cross shaft. Rotate the Girling back plates on the front stub axles so that the adjuster is at the back and the lever is at the front. The four bolt holes are evenly spaced and it turns 90 degrees easily. Use the really long 4” levers sticking upwards and cut down a Bowdenex cable to go from the top of the back plate towards the cross shaft. Cut the outer and cable with a grinderette. To shorten the inner cable carefully silver solder at the right place and cut through the centre of it, the solder prevents fraying. Remake using one of those adjustable square cable ends that clamp onto the cable. If the inner cable is damaged, the screwed end is often bent, make a new one up out of an early Mini handbrake cable.

Hydraulic brakes

Hydraulics will give more stopping power but there's quite a bit of work fitting them. Unless your car already has them or should have them like a Speedex or Super, it's a lot of work. On the plus side they are powerful (too much in some circumstances) and you can get rid of the heavy and low cross shaft. I have seen a set of Morris 8 brakes grafted onto A7 hubs. Somebody must have had a lot of spare time and machining facilities. The hubs had to be heavily modified to present the drum at the right place relative to the linings.

If you want to go ahead........ They were widely sold for specials in the late 50's and 60’s, quite a few were fitted to standard saloons. The basis is the 7" set up from the earlier Morris Minor or the Frogeye Sprite. The backplates are the hydraulic ones from the above donor with the centres cut out and a new one welded in to adapt onto the 'Girling' type axle ends with the right amount of offset. Don't try and make your own, there seems to be plenty of second hand ones about or if you're feeling flush new cast aluminium ones are available from Raeburns I believe. Cylinders, shoes etc then go on as per the hydraulic donor car. These go straight onto Girling front stub axle flanges, but the Girling rear axle flange has to be cut down the side to make it 'square' like the front ones. in the sixties you could get earlier axles machined down to take backplates. There’s still a number of these axles and stubs round so you can fit hydraulics (or Girling backplates for that matter) to a narrow axle if you want. The cylinder and springs are a tight fit behind the hub, which goes on last, and you may have to dress some parts like the backs of the wheel studs.

 

The ‘beehive’ springs at the centre of the shoes are hooked into the eye of a split pin , tensioned by pulling the pin through the back plate squashing the spring and then opening out the pin. The opened out ends are visible on the top of the backplate in this picture.

OK that's the easy bit done! Now mount a 3/4" bore master cylinder with a push rod off the brake pedal. The pedal may need reinforcing with a welded on plate with a drilled hole for the push rod clevis about 1 1/4” radius from the pedal pivot. Many use the Minor master cylinder like this picture but it is rather big and heavy, most of the specialist motorists dealers sell a range of cylinders either with or without an integral reservoir. This can be a better way to go. Make sure the cylinder is fastened very solidly or you will get a spongy pedal from the flexing alone. The chassis in front of the starter motor is popular. Plumb up with pipes (use none rusting 'Kunifer' or similar) and flexibles making brackets etc to suit. Mount a fluid reservoir to feed the master cylinder. Use Silicone brake fluid to prevent internal corrosion. Note that a larger diameter bore master cylinder will give a short movement, ‘hard’ pedal while a smaller diameter cylinder will give a longer more progressive ‘soft’ feel. You could experiment to match your taste and the response of the rest of the system.

Dismantling the cable is a good idea anyway, most of them are stuck very solid with old grease, once the cable is out a clean up and OILING of the inner cable makes a nice smooth action. One thing about open cables, it’s not much use greasing them. OK that’s better than nothing, but bear in mind that cables usually corrode on the inside first due to trapped moisture, the best way to look after them is with some thin oil that penetrates into the cable strands, leaving the new cable in the old engine oil dish before fitting is very effective.

The ‘Kench’ compensator

The 750 Companion describes an intriguing compensator that doesn’t involve having a cross shaft but works off the bottom of a normal handbrake lever. I’ve a suspicion that ‘Kench’ is actually a misprint, intentional or not, for Jack French. The drawing is slightly incorrect in the way the cables are fastened. Again it’s a balance between movement and force. You can see the proportions I used, I’m still waiting trying it out on a real car though.

The very last few thousand Sevens had full Girling rear brakes operated by a very short cross shaft. This has a lot of potential if you can get one. It’s almost identical in concept to the ones Jack French designed. It may hang a bit near the ground on a low special though.

Front, above, and rear on aluminium back plates