Drum brakes MOT fail/lubrication advice.

23 Feb 2005
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United Kingdom
Picked up a Mazda 121 recently as a runaround. Low miles and has been looked after but just failed the MOT on the following:

001) brakes imbalanced across an axle
002) Offside rear brake application uneven.

Measurements: RBT brake imbalance 34%

It was suggested that the brake might be binding.

Had a look, can't see anything untoward, but have ordered some new shoes. Don't know if it's worth replacing the cylinders too?

Have sprayed loads of brake cleaner in there, now I should probably relube it, but not 100% what to use where. I have white lithium spray, copper grease and CV moly grease to hand.

I'm guessing CV grease on the spindle (duh!) lithium on the bracket arm of the handbrake cable (behind the backplate) but what should I use within the drum itself, the shoe seems to move against the backplate at the top, surely that would need something on it?

The brakes in question are the same as this unit

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There's nothing to be scared about regarding drum brakes - one of the most important things is to ensure that the adjusters are working correctly - more later.
If the brakes are binding, one of the wheels will be difficult to turn when jacked up. You need both wheels up in the air for this, ideally.
With the drum off, tap the shoes inwards with a hammer. If the wheel cylinders are free, the pistons will move in. If they don't, they need replacing - same goes if they are leaking.
To get the best out of a drum brake system, they should be removed from the backplate (two turn pins with springs) and any sliding surface (3 on each shoe) where they skid on the backplate, greased. The handbrake pivot should be free as well. At the same time, a smear of grease on the wheel cylinder piston ends and at the pivot on the other end of the shoe does no harm.
If your car has the quadrant adjuters (like the video) these are the best sort. Basically when the shoes move out from the cylinders the adjusters have a ratchet tooth mechanism that keeps the shoes near each drum. The teeth on the adjusters should be clean with a wire brush, but not lubricated. Any adjuster pivot should be free also.
If you are happy with the shoe condition (one is thicker than the other, friction material wise) just roughen the surfaces with abrasive paper.
To set the adjusters, its handbrake on, then press the brake pedal. You may here the ratchet mechanism click as it takes up.
Apply the handbrake lever a couple of clicks. When the wheels start to drag, they should both be the same. There is a compensator on the handbrake cable that should apply equal effort to each cable - keep it lubed - its just to the rear of the handbrake lever, I think.
As you reasemble and put the drums on, give them a crack with a hammer to help centralise the shoes. Only do one side at a time, dismantling wise, so you can refer to the other if you forget where some part goes!
John :)
As I recall I always used Copaslip on brake components.
As I recall I always used Copaslip on brake components, just don't have it on your hands when touching the linings!!

Disposable gloves are a really good idea.
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I did pretty much exactly as burnerman on my brakes last year, copper grease on sliding parts and roughen up the friction surfaces (though I used a wire brush).

Went through straight away on retest. Rear brakes are generally under-utilised so there's little wear involved, and were not even subject to an imbalance failure until a couple of years ago!
I use coppaslip on the backs of pads and the like, but for other sliding surfaces ordinary grease will do.
An exception to this are pad slider pins as ordinary grease will attack the rubber boots so it's red rubber grease in there.
If you intend renewing the shoes, cover them with masking tape first to keep them clean.
John :)
Thanks for the useful tips John, and everyone else.
I got the bits off and managed to get the hang of reassembly when I was playing around with it yesterday, although there is a fair bit of up/down play with the shoes, but I guess they settle in where they need to go.

Just wondering what the benefit is to roughen up the linings? Does it make a big enough difference to change the test results?
If the linings are glazed or have slight contamination then it does no harm, but other than that, not really........the most common issue these days is the lining material separating from the shoe. This is due to rust setting in between the shoe and the lining - and the lining breaks free.
John :)
Right, have decided to replace the cylinder, it was slightly weepy, inspection showed a small cut to the rubber. Don't know if that's what was causing the problem, but best get shot of it.
Spent a good 2 hours hunting down my flared brake spanners today, finally found them in a box under a box. No idea how they got there! :mad:
Went to take the brake line off the back of the cylinder, wrong size!! :mad:
Off to Halfords for a 10mm, not my local Halfords of course, they were out of stock :mad:

Had to go to the next town. Anyway...

Got back, tried every which way to get the nut off, including spinning the cylinder by hand. Worst case scenario, bastard nut rounded off! :mad:

Had to use mole grip to get it undone.

So left with a knackered brake pipe nut, the pipe seems ok. Thinking about taking the 2ft or so of pipe to a garage to get the end cut off and re-flared, I'm assuming most garages will be able to flare steel pipe without a fuss? (It's in good condition and the other end that meets the flexi, came undone with no fuss)

Now thinking I should bite the bullet and get a half decent flare kit for future mishaps, are this type any good?

So long as the nut screws back in again, why worry - it happens all the time!
Just plaster it with grease afterwards and it will come out again if it needs to.
Most diy pipe flare tools work well enough, but do have a practice first - its much easier to get it right on the bench!
John :)
I was thinking that, and worry about it later. But when I say round, it's positively cylindrical! I could just mole grip it back on again I suppose!
Pull it through and fix to the new cylinder first.
Maybe file some flats on it, or is that being too fussy?

All sorted, I think.
Despite the MOT refusal stating 'Offside rear brake application uneven' I had a look at the nearside rear brakes, and found the handbrake lever was seized up! Crudded up and wouldn't budge by hand or with pliers. Squirted,cleaned and greased it, all good.

Makes me think the work I did on the other side was needless. :mad:

Would a fault on nearside cause the roller brake testing machine to register it as offside? Or have the garage got their sides mixed up!? (Near being kerbside)

The other concern I have is that the axle locknuts didn't seem to be that tight when I first undid them. They are the type with groove on the axle that you punch part of the nut into to lock it. Fiddly bastards! Haven't got a manual to hand for correct torque, but I know these are supposed to be a bitch to remove, and you're not supposed to reuse the nut :oops:
As I quickly interpreted your fault it was an imbalance between the two.

Seized handbrake cable would cause that side to brake harder.

I am surprised they did not notice that or condemn the handbrake.

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