Sticking rear brakes

[MK IA Norway Viking]

I did the same as you on my 1964 MK IIc manual with overdrive, in that I replaced the rear brake cylinders. Along with the brake pipes and flexi hose over the rear axle plus new pipe forward approximately to the rear end of the subframe. The parking brake mechanish on each brake cylinder was lubricated with copper grease.

Before putting any brake fluid into the braking system I mounted the brake drums. 

Both of them are stuck solid on the brake shoes - not possible to turn them. I turned the adjusting nut on the rear of the plate holding brake shoe assembly however it does not help. All I can think of is that the hand brake mechanism is not correctly set.

Any recommendations from club members ?

[lagain]

I hesitate to suggest this, but are the shoes on correctly. If you google 'brake shoe leading edge' all will be revealed.
If you think that the handbrake linkage is tight, just release the pins behind the drums as that will take off any tension.
Are they the correct cylinders for your car ?

[MK IA Norway Viking]

I will check these things - before I disassembled the brakes the same situation was present. The brake cylinders have been supplied by Mr. Wadhams so I am confident that they are right. The handbrake linkage is corroded so I will focus on this side of the braking system, to rectify the fault. As with everything else, I will prevail in the end ... :-)

[Phil Nottingham]

Are the new cylinders floating on the back plate?

Are the shoes the correct way round?

Are the shoe springs in the correct holes?

Are the adjuster tappets in the correct position?

If all the above is in order then some of the linkage compensators may be seized - the main one being on the axle. With the handbrake off these compensators must have some movement especially that on the rear axle which must move in 2 planes

[MK IA Norway Viking]

Good day Phil,

Thank you for your valued comments. 

Prior to dismantling, the drums could only be turned if the car was towed. Not possible to move the car by hand. I have the same effect now.

The new cylinders are NOT floating on the back plate. I tightened the screws/nuts fully before I mounted the brake shoes.

I should say that if I am able to make the brakeshoes contract 2-3 mm, the brake drums will rotate freely. I was able to make the drum fit over the brake lining and bring it all the way home without massive effort.

I believe the shoes are mounted correctly. I know that the upper shoe shall have "longer" lining than the lower shoe - I cannot tell a big difference, really, so I made sure to lay the shoes on the floor and out of the way. They were reftitted in the same way - unless I unknowingly ruffled them about.

Adjuster tappets and springs are in the right holes.

I cannot undo the hand brake arm from the rod that operate the two little discs that work on the brake shoes (hand-brake mechanism) because of corrosion not allowing the screw to come out.

I did undo the pivot for the hand brake rods by the rear axle. It MIGHT be that the remaining hand brake mechanism is not fully released, and still influencing the positioning of the brake shoes.


I see the comment about having the brake cylinders float - is it recommended to take off the brake drums, loosen up the brake cylinders to alter their position somewhat and then retightening them before attempting to refit the drums ?

[lagain]

If you look in the workshop manual it will tell you all you need to know.
The rear brake cylinders must be able to move on the back plate. I always put a smear of specific green brake grease on the back of the cylinders. I am not a fan of copper grease, it is too thin and washes off in the rain. I have used it on my motorbike on nuts and bolts and it has not stopped them seizing, green grease does not wash off.
Make sure that you use the correct nylock nuts and correct tiny springs on the wheel cylinder studs.

[MK IA Norway Viking]

Thank you - is it the same layout on both MK I and P5B ?

[Phil Nottingham]

The Mk1 has the same layout as the P5B apart from slightly different rear brake cylinders and a better X shaft for the hand brake linkage under the drivers seat

The cylinders MUST float to centralise them. This is a key part of the 1930s Girlng system that seems to be overlooked so often. There is no need to remove the drums to do this. Just slacken the nuts off a 1/3rd turn. There should be special double helix spring washers underneath the nuts called Thackerays.

As Lagain says its all in the WSM

You should also adjust the steady posts as set out in the WSM when new shoes are fitted. Do not pay attention to where the lining is positioned as it varies. The fully curved end rests on the adjuster and the stepped end on the cylinder tappets.  The springs must be in the correct holes and the correct way round.

I have emailed you photo of the springs position - I do not post photos in the forum but have posted many on the FB Groups (P4s have the same on the rears)