Rear brakes.... running out of adjustment..

[sandman]

Hi chaps,

I've encountered a strange problem on my car.... I'm running out of adjustment on the rear brake shoes.. The drums I'm using is virtually new (inside dia around 177mm) and the brake shoes are only worn down about 0,5-1mm - so there's plenty of material left on them. In order to get the drum to lock up I have to screw the adjust ment show all the way in.... I've also tried with a drum that had a slightly larger dia (180mm) and that wouldnt lock up at all - even when using new shoes...???

Anyone experienced this problem before?
Do the rear cylinders come in different lenghts/widths (i.e not only diff. cyl.bore)?

Is there a way to identify what cylinders are on (other than the bore)?

Hope someone can give me some quick help as I'm going racing on Friday!

[Matty]

It could be worn tapers on the adjuster screws, or worn tappets?

If you can get the drums to lock by adjusting the screws right in, then the problem is more than likely, to be play in one of the linkages or cable. Check the quadrants are moving freely. Ive also heard that the levers can have slight flex/play in them if they are old.

[sandman]

I should have mentioned this - adjuster screw and tappets all look fine... good as new.

I can get the drum to lock up when the screw is all the way in... but this has nothing to do with linkages or hand brake at all - it's avout adjusting the freeplay of the shoes/rearcylinders to avoid getting a low pedal.

[Matty]

What brakes are you running on the front?

If you can adjust the rears up so they just rub, and your pedal has long travel or hits the floor its likely to be something else, like front brakes adjustment out (if running drums). What size rear cylinders are you running, there is different sizes available, and this could be the problem.

[JC T ONE]

If the car is running drums, on the front ??

The most common fault, is most likely, that the "Christmas threes" isnt fitted.
These are the small springs, that sit on the brakeshoe, and is attached to the piston, in the wheel cylenders.
They hold the piston, against the brake shoe all the time, and a lot of people dont pay attention to them
On some wheel cylenders, have I seen springs inside, that keep the piston out, and these dont have the hole for the spring.

I have found this fault, on most Mini,s that come to my garage, with poor pedal function.

[bmcman.ie]

has this problem been getting worse over time, or have you replaced rear wheelcyls recently? it doesnt matter if quads/linkage are worn as this does not affect brake adj screw travel, both edges of the shoes sit into the slots of the cyls and tappet grooves, linkage only comes into play when h/brake is applied, ian.p.s. i presume the h/brake adjustment is right off and shoe springs are fitted?

[greyghost]

If the car is running drums, on the front ??

The most common fault, is most likely, that the "Christmas threes" isnt fitted.
These are the small springs, that sit on the brakeshoe, and is attached to the piston, in the wheel cylenders.
They hold the piston, against the brake shoe all the time, and a lot of people dont pay attention to them
.

my single leading front drums, don't have any spring to hold the shoe against the piston.
however my girlfriends twin leading shoe set-up does


check the clevis pin on your brake peddle, these have be known to "flog" out and add excessive travel. it might be enough, to not be moving the required amount of fluid, thus not letting the rears lock-up.

[Vegard]

He says he's racing on friday, so I guess he's not using drums at the front?

[JC T ONE]

my single leading front drums, don't have any spring to hold the shoe against the piston.
however my girlfriends twin leading shoe set-up does

Yes these special springs, are for twin shoes ONLY -

[greyghost]

i figured,
but there wouldn't be many single leading shoe cars left, most have twin's or disc's. apparently the singles are useless, all i've fould is they need adjusting more often.


back on topic.

the service limit on a drum is 179mm, so you 180mm drum is destined for the bin.
have the shoes been re-lined ?. this could have an affect on the adjustments, or are the new shoe's made correctly. it wouldn't take a big error to cause an issue like your describing.