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MG MGB Technical - Brake shoe springs

Stripping, cleaning and lightly lubricating the rear brake components annually on two cars for more years than I care to remember it's always a bit of a fiddle getting the top spring fitted after the lower part of the shoes is in place, or keeping it in place while I fit the lower part. It suddenly (eventually?) struck me that there was nothing stopping me fitting the spring on the front of the shoe webs, rather than the rear.

Did some Googling and eventually came across one picture of just that. Contacted the poster (classic restorer) who said he probably just refitted them the way he found them.

Last week I had occasion to strip one side of the roadster to replace the lever boots so took the opportunity to fit the spring on the front, once the lower part had been located on the levers and in the wheel cylinders but before locating the upper part in the adjuster, and it was so much easier. Drives just fine, MOT soon so will see what effect if any it has on the brake tester. The photo I saw had the lower shoe spring on the front as well, alongside the third handbrake spring, but there is no need to do that.


paulh4

I wonder if the spring is fitted to the back of the shoes for safety reasons?
It probably doesn't affect the braking as such with the spring fitted as per photo, but if the 2 she retaining clips happen to fail then there is a possibility of the shoes being pulled away from the brake backplate into the brake drum.
With the spring fitted behind the shoes any failure of the retaining clips would just push the shoes against the back plate and braking efficiency would be still there.

Just my thoughts - probably unlikely the retaining clips would fail!
AdrianS

That was my concern, although very slight, and it was more about causing binding than lowering efficiency. Even if a retainer failed the shoe would only move out a bit, and with the webs sitting in the adjuster and wheel cylinder slots, and the lower spring pulling them towards the backplate (in my case, I wouldn't put both springs on the front), I can't see it doing that anyway. With the retainers being fitted last there was no tendency for the shoes to come away from the backplate that I can recall.
paulh4

Paul
Fully agree with your method, I've been doing that for ever-
I usually get all the bottom together with the spring on the inside,sit one shoe in the top adjuster and fit the retainer pin/clip to that shoe,fit the spring to the outside then stretch the other shoe over onto the other side of the adjuster and fit the other pin/clip
works for me
I figure that with one spring on each side it's all neutralised and sits there unloaded eitherway

willy
William Revit

Hi Paul,

Did similar to our B/GT about a year ago. Wish I had known earlier, you make it look easy mate.

Photo a bit out of focus........

Lazza

LC

Another tip is to fit the spring so the coil is lower than the wires, if it is above then when the shoes are correctly positioned against the backplate for the drum it can rub on the adjuster. I've always found that when first fitting the shoes one has to be slid down quite a bit and the other up, to get the drum back on, even with the adjuster backed right off.

The handbrake spring also has a 'preferred' orientation so things fit without being bent or rubbing, and even the lower shoe spring has options.

For that it's whether to position the long arm of the spring that comes through the shoe, above the handbrake lever (as you and I have it) or below. Haynes shows it above also, but John Twist puts it below. From my reading that long arm is an anti-rattle measure for the handbrake lever, and should be positioned above so the smooth curl at the end of the arm is pressing down on it. If fitted underneath the sharp/rough cut end of the spring is pushing the lever up. Rattle has never been an issue in the decades I've had either car, but above is more aesthetically pleasing.

Other variations are:

Both shoe springs should go through the holes at both ends, not the slots - just a nicety.

The levers themselves are handed or it makes the drum difficult to fit and the brakes to work correctly.

The shoes should be installed so that when travelling forwards a point on the drum will pass over the 'empty' portion of the shoe before reaching the friction material (as both yours and mine are).

I've not counted how many different ways there are of assembling the back brakes, but I'll bet it runs into the dozens.
paulh4

I've always struggled with the near side knowing which way around to put the shoes because that side isn't show in the manual. I always hook the springs in the slots where I can not the round holes. I cant figure out what leading shoe means. I found some pictures on the net to help me. I put the springs behind the shoes and then engage them in the slots in the cylinder then the adjuster.
Paul Hollingworth

Leading shoe: Literally hundreds of pages and illustrations of this through Google.

With a single wheel cylinder as on the rear brakes of the MG there is one leading or primary shoe and one trailing or secondary. With wheel cylinders top and bottom you could have twin leading, one of each, or even twin trailing if you were being perverse.

Descriptively: Leading (or primary) shoe is a term referring to the shoe that moves in the direction of rotation when it is being pressed against the drum.

That's difficult to visualise as the drum is going round but the shoe moves outwards, some of the diagrams with arrows may help. It also reverses with direction, so the MGB has one leading shoe no matter whether it is going forwards or backwards.

Put another way if a point on the drum reaches the end of the shoe that is being moved by the wheel cylinder before it reaches the end on the adjuster, that is the leading shoe. The relative movements tend to make the shoe 'bite' into the drum with a self-servo action which gives more braking effort.

In the attached, which is of the left-hand side, when travelling forwards i.e. the drum rotating anti-clockwise, the shoe on the right is the leading shoe. That makes it the rear shoe, and it is the rear shoe on the other side as well because the drum is rotating clockwise in that case.



paulh4

This thread was discussed between 24/04/2019 and 25/04/2019

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