Can someone explain... brakes

On an old 88 series 3, the trailing brake shoe doesn’t have enough strength (under the power of the bottom black spring) to return the brake cylinder back into its housing. On the top, the red spring attaching the forward shoe to the tab on the backing plate has enough strength to completely push the cylinder back into its housing. Am pretty sure it’s normal as both the old and the new set of brakes were the same (and makes sense given spring leverage) but curious to know the reason for the design and if this is normal? Am half expecting the brakes to drag when fully assembled. Photo attached. Please don’t comment on the locking tabs. The Brit part ones needless to say didn’t fit so I loctite 270-ed them and using cut off tabs as washers....

A couple of thoughts (my brakes are different):
1 Don't tank anything for granted, I've wasted a lot of time trying to refit something the way it come off only to fid it was put together wrong.
2 Am I right that the piviot is floating? If so pulling the leading shoe in will take pressure off the pivot end of the trailing shoe.

Hi Rob. Piviot is fixed. Am pretty certain this is the correct spring setup and it’s as per the set I removed. Until I put the drum on, I don't know if it’s an issue, I just like understanding these things. Feel it makes you a better mechanic. Tom

I would agree The bottom spring would not pull the top shoes in , I think it’s there just to keep both shoes on bottom pivot
The red spring should not necessarily pull the piston right in , more so to keep shoe pulled onto adjuster , how far the piston goes in is dependant on where the cam is adjusted , they shouldn’t drag if adjusted ok

Your missing a bit. 10" SLS has floating trailing shoe, not a very clever design, it often snags in reverse.

That makes more sense! Also looks a bit too clever for its own good.

The trailing shoe [without top spring] you will find you have to push it in to get the drum on. At the moment the spring inside the cylinder is pushing it out, some manufacturers that spring is to strong. once fitted and road test you may find reversing is an issue as the lining on trailing shoe will self servo and apply itself.
Looks like you have chamfered linings sufficiently at top edges did you do lower edges at all.
Your bottom spring looks a little bit thin to me have you got the originals to compare them with.
The bottom spring on attached pic shows what I mean about thickness.

Thanks Blackburn. Sure enough need to push trialing show in to get drum on but it such a powerful push the drums have zero chance of rotating. They’re brand new Delphi drums. That seems like a mamouth design floor if the drums are too powerful for the brakes? I just can’t see how this is going to work. Video to assist you

Did you check the thickness of your bottom spring ,normally I would have gone along garage and measured an old one but had a heart attack last monday so not allowed in there at the moment. [I am fine two stents and some medium scarring on heart muscle which should heal]

That video doesn't look right to me, the piston shouldn't push the shoe back out unless there is pressure somewhere. Have you bled the system? If there's air still in the you could be compressing it

Is it possible that the pedal push rod is worng and not allowing the fluid back into the master cyl? Combined with air this could push the slave out. What happens if you open the bleed nipple?

Hope you’re okay Blackburn - sounds nasty.

Cylinder isn’t plumbed in yet so don’t know about air bubbles but if no fluid or air in system and pipes all open, shouldn’t make a difference.

Responses crossed - not connected to brake lines yet. Obviously the spring in the cylinder is stronger than the spring depressing the shoe into the cylinder. I fear this could be a bit of a headache.... but must be the same for everyone. The lower mounting of the return spring on the trail show just gives much less leverage on the cylinder.

thspeller said:

Responses crossed - not connected to brake lines yet. Obviously the spring in the cylinder is stronger than the spring depressing the shoe into the cylinder. I fear this could be a bit of a headache.... but must be the same for everyone. The lower mounting of the return spring on the trail show just gives much less leverage on the cylinder.

Click to expand...

My s2 is the same set up, no issues when reversing etc
Fit them and dont worry

The picture I posted in post 7 is the same situation you are quoting ie no fluid in cylinder the trailing shoe is pulled back in by the stronger spring in my photo.

As lynall says just fit and forget, series brakes have been happily working for over seventy years.
If the rear shoes spring was able to overcome the slave piston spring and push it all the way in then you would end up with a lot of movement at the brake pedal .