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MG MGB Technical - Brake shoe/drum refitting problem

Hi,

On a 72Gt I have replaced brake shoes on one side (will do the other when I sort this problem out!!).

The shoes are new, the adjuster is fully backed off, the two metal cylinders are touching. The springs are located correctly, as is the brake lever arm and the shoe ends snug in the adjuster and cylinder slots. Also, nothing seems to be fouling.

However, cannot get the brake drum back on, no wear rim etc on this; it is a newish item. Putting on the handbrake doesn't move the shoes, too much gap between the levers and the metal slots of the shoes.

Could the brake cylinders be seized in an on position. They do seem to be properly retracted (i.e. in) or is this be a banjo axle shoe set that I have (Does anyone have the part no for the shoes. Or, can anyone think what else it could be.....
Iwan Jones

36 - Brake shoes - Set of 4 GBS740 [36] - Price: 21.50 Including VAT at 20%

30 - GBS740 - BRAKE SHOES - 21.95

gbs740 - REAR BRAKE SHOE SET - MGB

have a look at Paul Hunt's excellent site - http://www.mgb-stuff.org.uk/braketext.htm#

I hope these John Twist vids might help too -
19 MG MGB Rear Brakes - http://www.youtube.com/watch?v=vomcvvpv-2Q

146 MGA & MGB Rear Brake Adjustments - http://www.youtube.com/watch?v=xmcaxLzEq6k
Nigel Atkins

Hi,

Many thanks Nigel, apart from confirming that there is a difference between mga and mgb brake shoes (but none between mgb): I'm afraid the very good John Twist vids are not much help in my case.

[Please note Paul Hunt has the top springs in both of the circular holes, John Twist has them as per Haynes .... one end in hole the other in the slot .... tried both & yes, I've looked very carefully at all the usual troubleshooting sources]

The Unipart brake shoes I have seem to be the correct ones. I've put them on and taken them off about five times, just cannot get them to come in enough to get the drum on.

Ho hum, I'll take the cylinder off next. Though this seemed to expand/contract ok when pedal power was applied.

Brake lever seems to be correct, no excess metal as per Paul Hunt's problem. How much from hinge centre to outer end should there be?

Any other suggestions anyone?

Iwan Jones

Iwan,
Give us a picture if you can. Double check the orientation of the shoes, particularly the hand brake expander location. If pulling on the handbrake doesn't move the shoes look at; The pivot on the back axle, it does seize up and stop the shoes fully retracting. Try removing the clevis and see what happens.
Also check that both pistons are actually moving and one or both are not seized in their bores.
Allan Reeling

Linings thicker than spec? I have seen it happen. Only an issue with new/new-ish drums, worn ones are more accomodating.
Paul Walbran

Also, make sure that the brake adjuster has its followers with the pointed end away from the backing plate. If reversed, it will make the brake drum impossible to install. RAY
rjm RAY

Hi,

Thanks Allan but handbrake cable is disconnected, when I move lever as it would/should work with cable connected, nothing moves. Going to check on something catching/fouling again tomorrow. Might even shorten lever end as per Paul Hunt web info. Thanks Paul, yep new drum and thick looking lining. That's the next thing I'll check. Adjuster cylinders the right way round. Thanks Ray.
Iwan Jones

Hi, adjuster cylinders have been in correct position all along. Last comment above makes it seem that I've only just noticed it. Pistons do move ok but putting on a new cylinder as a matter of course in a little while. Thanks all.
Iwan Jones

Have you compared the curvature of the old and new shoes?

Try laying the new shoes in the drum and seeing if the ends touch but the middle doesn't.

What's preventing the drum going on? If it's the shoes it should be obvious as a dull sound, if it's metallic it's something else. Also the shoes will prevent the drum going on at all, i.e. it won't overlap them, but if it's something else the drum could go over the shoes a bit then stop.

In my experience the shoes always go off-centre if left to their own devices, and I have to tap one down and the other up before fitting the drum. Look at the gap between the face of the shoes and the stepped flange around the edge of the backplate and make sure it is equal all the way round before attempting to fit the drum.

Paul Hunt

Hi ,

Thanks Paul, think its a combination of things. Going to replace the cylinder, as only one side seems to be retracting properly, other very stiff indeed. You are right, the shoes are weirdly curved. You would think that basic items like this would work ok straight from the box. I think they were bought in an autojumble.

Don't have the old items, not my car.

New ones have been ordered.

Iwan Jones

"Going to replace the cylinder"

Just had that one side of the V8, and a leak on the other, so replaced both. You would be well advised to check the bleed nipple is clear before fitting. When bleeding mine I couldn't understand why one side no fluid came out of the nipple, then I found it running down the inside of the back-plate - the nipple was blocked! Fortunately a drill twisted by hand down the outer bleed hole cleared whatever was causing the problem.
Paul Hunt

This thread was discussed between 02/11/2013 and 06/11/2013

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