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MG MGB Technical - Handbrake issue

I've a '72B Roadster with standard rear brakes. The issue I've got is that the handbrake levers within the drums don't fully release so that the shoes are partially seized against the drums. I've taken everything apart and the levers are free to pivot and move in the shoes. The brake shoes are newish.

What I've noticed is that the pull off springs (again, not that old) don't pull the lever back completely. In other words, you can pull the lever back some more to further release the shoes. It would appear as if the springs aren't powerful enough, but as said, they're not that old.

I can back off the brake adjusters, but as the shoes are new as there's not a lot of leeway. As soon as the handbrake is applied, back to square one - brakes seized again.

Anybody else had this issue? Are stronger springs (non standard) the answer?
Peter Allen

Is this when applying handbrake, footbrake or both? Both sides or just one?

If only footbrake it could be the wheel cylinder pistons partially seized and that's likely to affect one side first - unless the car is ne to you and it's always been like this.

If only handbrake is the cable fully releasing? That will affect both sides. If it's the levers not releasing then there should be some 'slack' in the cable where it attaches to the levers, but if it's the cable that will still be under tension.

If the springs are newish it could well be that they just aren't as strong as the originals, not something I've ever changed.

Check the notches in the levers don't have a ridge that is locking behind an edge on the shoe, these wear and can need welding up eventually to get best operation, which is when the section the cable attaches is parallel to the back-plate when applied.

The adjuster only alters the top of the shoes of course, the levers act on the bottom and should lift the shoes up in the wheel cylinder piston grooves so check there are no notches there either. Once the lever pivots are free there should be nothing preventing the shoes from seating back in the grooves again. I strip and clean my rear brakes annually, putting a smear of grease on every metal to metal contact point in the system i.e. adjusters, where the edges of the shoes rest on the backplate, where the levers act, etc.

paulh4

Are you sure you have the springs in the correct locations? Mine look like this and work fine. This is the right hand wheel.

Mike Howlett

Thanks, chaps.

Mike - yes, my spring is attached the way yours is.

Paul - thanks for your thoughts.

This is just a handbrake issue. Wheel cylinders not seized and both sides of cylinder move OK. Yes, there's slack in cable.

Suggestion of ridge in lever a good one - I'll check that. I've now a feeling of deja vu on this (I've had this car 38 years!) and a similar issue may have prompted me to buy new levers in the past. Looking at Mike's picture, I might have a little stretch in one coil on tension spring. I'll compare strength with an old salvaged spring - I seem to recall more oomph needed in the past to hook these springs it into the lever and I can't be getting stronger! Also minimal lifespan perished rubber boots can't help.

Your point on stripping down the rear brakes annually chimes. If there's one area of the car that requires a disproportionate amount of maintenance it's the rear brakes. I've found it wise to have a spare set of components on hand - the times I've discovered a seized wheel cylinder or thread gone in an adjuster.
Peter Allen

I've had MOT-ers say how good the roadster handbrake is, adding "normally they are rubbish"! The V8 was the same until I changed the shoes because of a fluid leak. Initially it wouldn't hold the car on even a slight gradient, several sessions of sanding down high-spots on the shoes to get an even wear pattern improved them slightly, but even 10 years later they are still not as good as the roadster.

The other thing I check annually is that the wheel cylinder pistons move, I've found those seized in the past as you say. And ditto, the rear brakes take more time and effort than anything else!
paulh4

Thanks for your earlier suggestions.

A postscript: I took it all apart, nothing looked particularly worn, so I greased up all interfaces (other than the linings!) and re-assembled. The conclusion I came to was, yes, the brake lever could still move in further on both sides, by hand, but that was an artificial construct. I just adjusted the brakes on basis of where the levers naturally returned under spring pressure. Footbrake on and off a few times, and same with handbrake, and I seem to have achieved (hopefully) non binding rear brakes, but with a decentish handbrake.

Peter Allen

This thread was discussed between 05/01/2023 and 09/01/2023

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