Rear Brakes Binding

[JeffW]

I am completely at a loss to try and get my offside rear drum from binding.

I have:

1. Replaced drum and handbrake actuating lever
2. Replaced shoes and all springs
3. Ensured ratchet is correctly installed and the 'nose' points at the shoe surface.
4. Replaced brake cylinder
5. Bled brake cylinder
6. Chamfered top of shoe material (it was already but I did some more).
7. Dremelled away metal from the top of the shoe as per the post on here 'Rear Brakes - Drat'.
8. Tried 3 other drums (old and new) and all bind.

No matter what I have tried, it binds at the top. I have even dremmelled away shoe material yet it still does it.

Some photos attached: Top spring is behind shoes, all is very snug and the handbrake works (it does bind with the cable detached as well) and the ratchet clicks up nicely when I press the brake pedal.

If anyone has any idea I would be most grateful for any advice.

Thanks
Jeff

[trunt]

May be worth checking the lead shoe/trailing shoe thing… look at the drawing posted by Richard here that shows the larger gap of the friction material at top left, and it appears to be for the left side of the car

https://socforum.com/forum/forum/stag-owners-club/soc-forum/825923-bleeding-and-handbrake#post825941

[JeffW]

Sorry Terry I don't understand. I thought the shoes were identical and just flipped around to match whichever side you were working on. I am replacing the driver's side rear, whereas the picture Richard posted from the ROM shows the passenger side. My leading edge on has the large gap in the material, but it is top right as it's the driver's side.

[Philip Wardle]

Is the flexible brake hose ok Jeff? They can work as a one-way valve if collapsed inside.

[Goldstar]

Is the flexible brake hose ok Jeff? They can work as a one-way valve if collapsed inside.

Great shout

[JeffW]

Hi Philip & Paul

They were replaced by the previous owner a year ago and the fluid seemed to flow easily back and forth when bleeding.

Also it is definitely binding at the top (leaving tell-tale marks on the shoes), yet they are snug in the top bracket with the two rivets, so not sticking out.

But thanks - if all else fails I guess I will be replacing the hose as well!

(Oh and the shoes move nicely back and forth in the cylinder, as seen on the Tony Hart Stag maintenance DVD).

Jeff

[flying farmer]

Is your backplate bent?
It seems you have replaced every other component and the problem hasn't gone away, which suggests the one remaining component may be the problem

Neil

[JeffW]

Hi Neil

I was just mulling that too as a process of elimination. After trying 2 sets of shoes and 4 drums there must be something else.

I will disassemble again and take the driveshaft out to see how the plate looks. TD Fitchett has some NOS backplates which may come in handy.

Thanks for the suggestion, appreciated. .

Jeff

[APS]

Hi Jeff you say they are binding, is this what you are feeling by rotating the drum by hand ? or after the car has been out for a drive ?
If the former they may just need centralising by a few good stamps on the brakes whilst out driving. If properly binding I would imagine the drum being very difficult to remove.

Or perhaps try fitting the brake shoes loose in the drum and they have equal gaps and that the shoes are not distorted in anyway.

[wilf]

Is the witness mark on the linings across the whole width or just mainly one edge?

[trunt]

Sorry Terry I don't understand. I thought the shoes were identical and just flipped around to match whichever side you were working on. I am replacing the driver's side rear, whereas the picture Richard posted from the ROM shows the passenger side. My leading edge on has the large gap in the material, but it is top right as it's the driver's side.

Got my offside/nearside thing mixed up! yours is on the right side!

[APS]

Just been thinking about this a bit more. If they are new brake shoes then a little binding should be expected on the top part of the shoes. They will soon bed in with some driving.

Reason I am thinking this is because when braking the shoes only pivot at the top, they are not pressed out against the drum by the wheel cylinder at the bottom, where there is a lot more movement. If there is too much clearance between the top of the shoes and the drum you might find that you get hardly any braking effect from top part of the brake shoes as you would need much more pivot action. Ideally I think you want the shoes at the top being almost touching the drum without binding when not braking so they do not have far to travel to touch the drum when braking. To get that I think the process is for them to binding a little when new, but quickly wear down to being hardly touching after a few miles.

If binding a lot, then my theory is a load of bs. Just a thought and I could be completely wrong of course.

[JeffW]

Hi Jeff you say they are binding, is this what you are feeling by rotating the drum by hand ? or after the car has been out for a drive ?
If the former they may just need centralising by a few good stamps on the brakes whilst out driving. If properly binding I would imagine the drum being very difficult to remove.

Or perhaps try fitting the brake shoes loose in the drum and they have equal gaps and that the shoes are not distorted in anyway.

Thanks APS.

This is the perplexing part, drum goes on easily and comes off easily, yet rotating by hand it binds at the top. Jacking up the car and putting it in gear, the left hand side spins freely but the right hand moves only a bit unless you assist it by hand, then it rotates 360 degrees and then binds again - as if the drum was terribly out of round. However it does it with all 4 drums I have and 4 sets of shoes (new and old).

I did take it for a drive and the brakes felt fine, but on return home the drum was extremely hot and I could smell burning or well toasted brake lining.

On your second point, I am also stumped why it only binds on one side. The left also has new shoes, new drum, new springs, and works perfectly. If the new shoes bind then both sides should bind to being with, shouldn't they?

Thanks for the theories though, I may try another drive before taking it all apart again, which I am greatly tiring of.

Jeff

[JeffW]

Is the witness mark on the linings across the whole width or just mainly one edge?

Hi Wilf

Sorry I forgot to take pictures. 3-4 shiny spots on both shoes near the top of both shoes (nothing on the bottom or mid-section), and they are not across the width and in very random but consistent places. I dremelled away some of the shoe where it was marked and it still reappears after reinstalling the drum.

Thanks
Jeff

[jbuckl]

1. Look for anything that is stopping the shoes from floating. Lightly lube the backplate contact points with high temperature grease.
2. After 1; There were some issues with new drums that had not been machined concentrically … check for runout between register & friction diameter…. Unlikely though.