Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Rear Brake Shoes

Perhaps returning to basic thinking could be of some value...? GoMoG information is the result of years of the experience of many hands on Morganeers and professionals of all types, added to very many miles travelled in different countries if not continents by the webmaster there, thus would seem to be quite the best source of information available with no charges attached, of course there may be those who think differently.

Basic thinking.... If the brakes are sticking on in ANY way, then that will show up as heat on the disc or drum after a very short journey of a few hundred meters/yards where the brakes have been applied BEFORE starting the run, this will show up as the affected drum/disc as being HOT to the tough, perhaps hot enough to burn skin... take care..!!

If heat is felt, this should be looked into, in a worst case scenario the heat can build up and feed into the brake fluid which can boil to the extent that on the next occasion brakes are required the brake pedal may have little effect in terms of applying the brakes..!!

The pics of the rear drum brake system show a double acting cylinder.... it has one force applied by the brake fluid that operates two pistons directly acting as the result of that one force... the designed of the brake system using this type of cylinder/piston arrangement depends upon both pistons being free to move equally relative to the applied pressure..... With the possibility of corrosion build up more on one piston more than the other the BALANCE of the operation is lost to the extent that one brake shoe can wear more than the other.

This imbalance may not be detected easily and may not be found until the drum is removed during maintenance.

IF one shoe seems more worn my first check might be to have a look at the rubber outer boot on the end of the cylinder that operates against the less worn shoe.. if there is any fluid found then it could have caused either the piston to corrode, or may be a sign of a leaking piston seal.. I have found both corrosion and leaking seals though the latter in an advanced state usually shows up with damp back plates, and if allowed to continue will eventually contaminate the drums and shoes with brake fluid..

On the other hand if one of the pistons has corroded it may take much more brake pedal pressure to force it to move, and logically(?) if it is harder than normal to get it to move out, it will be harder for the brake springs to make it retract, thus the shoe may stay in contact with the drum in varying degrees from a light rub to something generating ever more heat..... The latter can be discovered after HEAVY braking where the extra force applied caused a sticking piston to move out of position and stay out..

My usual quick test is to employ a long screwdriver, engaging it`s tip in the flange of the brake backplate, approximately in line with the centre of the arc of the brake shoe and using the screwdriver as a lever, I lever the shoe in the opposite direction to that of it`s normal travel when the brakes are applied, observing the pressure applied and the amount of movement of the piston attached to that shoe.... it should be seen to move reasonably easily.

I do the same on the other shoe which if all is well not only move similarly but also cause the other piston to act on the other shoe.... in which case... all seems well, other than now the shoes will not be centralised with the drum, and require a bit of fiddling to get the drum back on... after the brakes have been operated the shoes should then be centralised once more..?

If a sticking piston is not discovered when looking for the cause of an overheating brake drum or excessive wear on one brake shoe compared to the other, then the cause could be handbrake related, as any stifness in it`s operation could hold the rear brakes ON partially in varying degrees...?

The handbrake mechanism if not adjusted correctly and free in all aspects of it`s operation can cause all sorts of issues.... but then it seems possible the GoMoG article may have addressed that..?

Try to stick to basics when fault finding that way you may gain a better understanding of the way things are supposed to operate..?

My thinking could be well out of date on any subject thus perhaps best to treat it with a degree of scepticism.. Happy to discuss further if thought to be of any advantage..?

Lots of interesting stuff there Luddite but bear in mind the indisputable fact the the linings when new are thinner on the trailing shoe than on the leading shoe, so one could end up looking for a problem which doesn’t actually exist.

Thanks for the heads up Doug.

I have not ever had to replace brake shoes on my Morgan and would have been surprised to find one shoe having more lining material on it than the other, likewise on any other vehicle, though in truth I have never ever measured them as new on any vehicle, right back to the days when the linings were riveted, and I used to rivet new linings in place..? I suspect were that the norm then I might have read or heard of the requirement to select a thicker lining for the leading shoe... hmm..? As they say, every day is a school day.. and I suspect I have forgotten more than I remember... (-:

Logic(?) would seem to suggest if there was no heat build up on a drum or drag detected once jacked up, and the drum not difficult to remove, then perhaps one might not be looking for a brake issue, though one could still be hiding in there..(-:

Just for reference if of use to anyone, these are official AP Lockheed (now Caparo) details of the rears - you can clearly see the thicker leading shoe

Both shots are Left / Nearside (drum rotating anticlockwise)

You can also just make out part of the self adjuster ratchet, just below the Y47 marking on the shoe web

Thanks for the heads up John... every day is a school day right enough.. (-:

Thought perhaps that I would add/update this thread with my findings so that anyone finding this thread can read further:

Well yes, as stated the leading shoes on the rear brakes are indeed fitted with thicker brake lining materiel, more than twice as thick in fact from new. I have never been able to obtain a definitive answer as to what minimum thickness due to wear is the lowest limit thickness of lining material. However the leading shoes do tend to have the greater wear and I have reached the conclusion that the trailing shoes must have a harder material for their lining as having a duel piston which if working correctly will apply equal pressure to both shoes as they engage with the drums. so, I gauge my wear limit to be when the lead shoe approaches the thickness of the trailing shoe, about 3mm remaining. The lead shoe is also the most effective shoe for breaking efficiency or in the case of drums fitted with two separate pistons the one leading edge of each shoe. I feel that this is part of the design of the rear drums in that the breaking effort is almost in total acquired by the leading shoe with the trailing shoe only applying the required force to allow this to take place and the harder lining material which not only restricts wear but also reduces harsh breaking to the light rear end, this prevents the rear of the car breaking away which is more likely to happen when pushing your driving style.

Disc brake conversions.... yes they work and yes you need to fit an adjustable regulator to restrict over breaking at the rear.

Disc brake conversions work best with the Quaife axle the BTM has issues in that it has a built in end float which should be set at 1.2mm (not adjustable) which is not too bad although I hate not being able to adjust this out. However it is not unusual for this end float to exceed 6mm now this is not noticeable under breaking with drums fitted but with discs you have to centralise the disc and calliper alignment and racers using them have to dab the breaks quickly before applying pressure to centralise things first, not so easy on cornering though! The drum set up is perfectly alright if serviced correctly. The pistons do seize up and in my experience its not due to rust, rather it's like they gum up as the piston lubricant becomes sticky and they can be well stuck. Dealers seem to have two options for fixing them, firstly they just change the cylinders with the associated brake rebuild and a lovely remuneration for them into the bargain as well! and second option is they pop the drums off and tap the pistons from side to side until its loose enough to pass a brake test and that won't last for long until they re-seize again! there are a lot of later classics out there without the rear brakes working properly as the front disc's are good enough to stop a light car like the MOG. A hand brake test makes you believe they are working fine but they certainly are not!

Is there a solution which won't break the bank? Well yes there is, I have never stripped a modern classic whereby the rear cylinders have required anything more than a service and a repair kit which is readily available for under £30.00. Yes the overly complicated rear drums are a pain in the proverbial but learn how to do this job and things start to look a lot better and cheaper too. The auto adjuster is also weak and requires to be cleaned and serviced so this can be done at the same time. I keep a set of spare cylinders serviced and ready to go but in reality a simple clean and polish with the cylinder body still attached to the backplate is all that's generally needed. Just one further note. This gumming up of the cylinders does not seem to be as a result of hydroscopic water absorption of the brake fluid causing rusting. I have for many years used red rubber lubricant and I'm sure this sticky gloop is responsible. The rear brakes are so lightly used the heat never really builds up in the rear drums and its not combined into the brake fluid as you would expect so I am now trying alternatives but I remember that as a youngster servicing older generation cars at work 1960-70's we would use vaseline to lubricate the cylinders and never had any trouble and these cars would have been much like a Morgan in the level of rear braking effort and believe me we seldom fitted new cylinders and would fettle and fit repair kits unless they were totally shot.

Sewin, have you tried Mintex Ceratec ?

There's a few copies around, but I've stuck with pukka Mintex and found it very good as both a high temp touch point lube for disc pads and anti seize on the RW cyls

Yes I've got mintex ceratec and use it for pads etc. never thought to use it on cylinders, although last year when I serviced my sons VW polo I did use it on the cylinder that I needed to service as I couldn't lay my hands on the red stuff!. At the moment I'm trying ATE Bremszylinder-paste, on the rebuild I am just finishing in fact, this is the first time so I'll see how it goes but red rubber grease I'm sure is the problem, It seems all the time you are using the car it manages to stay fluid enough but as soon as you lay it up for winter it sets like toffee! Many swear by brake fluid as a lubricant on servicing a cylinder or installing a new one but I'm not a fan and don't find it promotes a good barrier seal, rather a fluid track for weeping. whereas a purpose made lubricant stays where put and also protects the outer aspect of the piston and seal behind the dust cover. Thinking I might just go back to petroleum jelly. easy to apply and allows the correct surface cover and I never had a problem with them seizing up in the winter lay off!