Rear Brakes

[Ingles49]

This may be very stupid and I think that I know the answer but I want reassurance before I start stripping things off and buying new bits. I have a Minor 1000 (950) with 7 inch brake drums. When I was adjusting them recently I couldn't get them to rotate freely, there was always quite a lot of drag (too much). I took the drum off (its in good condition) and discovered that pressing the brake pedal with the drum off only moved the lower shoe not the upper. Equally the adjuster works directly on the bottom shoe and moves that but the upper shoe does not move. So here is my question, am I correct in thinking that the cylinder is not working or what else explains my symptoms. Thanks in advance.

[philthehill]

The cylinder has to be able to slide in the backplate so as to centralise the shoes in the drum.
The snail adjuster will only adjust the shoe against the snail adjuster. The brake pedal has to be pressed down the centralise the shoes in the drum. The snail adjuster can then be adjusted again and again until the shoes are finally and fully centralised and in their correct operating position.
With the brake drum removed the piston in the cylinder will only push out that shoe against the piston/snail adjuster. Because there is no drum to centralise the brake shoes the cylinder will not move in the brake back plate.
Make sure that the cylinder slides freely in the back plate. If it is free and sliding then all will be right when you adjust the snail adjuster.

[Ingles49]

Thanks for replying Phil, but I'm afraid that I'm even more confused. If the cylinder is bolted to the back plate how can it move?

[ManyMinors]

The cylinder is not bolted to anything. It is partially secured by the brake pipe and handbrake connections but is free to slide up and down in the backplate - which it needs to be in order to operate - exactly as Phil has explained above.

[philthehill]

Ingles49
Just to be absolutely sure - are you describing the front brakes or rear brakes even though your post is titled 'Rear Brakes'?
From your initial description I considered that you were describing the rear brakes.
If you are describing the front brakes then you have a lazy or seized wheel cylinder.
The second or lazy cylinder will not move until the first cylinder has pushed the lining/shoe against the drum and then the second or lazy cylinder is forced by the line pressure to move.
There will always be a first to move cylinder even when the second cylinder is free.
To get over the lazy or seized cylinder you need to either replace or overhaul the cylinder.

[geoberni]

As others have said, each side of the REAR brakes only has a single cylinder. It has one piston which pushes out in one direction only (down in this case); then when that lower shoe touches the drum, further extension of the piston forces the cylinder to move in the opposite direction (upwards) pushing the other, top, shoe against the drum.

20210613_125443.jpg (695.44 KiB) Viewed 3367 times

There's no Bolts. So which brakes are you talking about....

[saffrons]

When you press the brake pedal and only the lower shoe moves, it indicates that the upper piston of the wheel cylinder might be stuck or not functioning correctly. The adjuster typically adjusts the lower shoe, but both shoes should ideally move to some extent when the brake pedal is pressed.

[philthehill]

Minor brake wheel cylinders have only one piston per cylinder - there is no upper piston.

[geoberni]

See this video, obviously made by someone complaining about a new cylinder he's brought, but that's irrelevant at the moment.

See how the cylinder is not secured and is supposed to slide up and down.
That's how single piston operates both shoes....

https://youtu.be/9TuArPAPp-E

[myoldjalopy]

Where is the quality control on these things? It is not uncommon now that there are variations in spare parts - not so long ago I bought lockwashers for the front suspension - only one would even fit!

[Classiccars]

Yes parts seem to be pot luck.I read about people complaining that new head gaskets were blowing.Put ours on and it split between the central pistons so bought the upgraded sort Payen I think.No probs since.

[philthehill]

You only gets what you pays for.
If you pays cheap you will get cheap.