Help Please .. BN 1 Rear Brake seizes on

[ianh]

The rear nearside brake on my 1954 BN1 snatches and then sticks on.
If I try them in reverse they work fine ?!?


So far I have tried :
Repositioning several times and checked they are not on the wrong way round
Overhauling cylinder
Un seizing handbrake
Relining brakes
Chamfering leading edge of shoes

Drum is lightly scoured but seems ok
Return springs also look in good shape

I have run out of ideas can anyone please help before the whole summer goes

Many thanks

Ian

 

[Basil]

I'm sure someone will be alomg who can answer your question, but I just wanted to welcome you to teh forum and say congratulations for putting our number of currently registered members over the 5000 mark!

Basil

 

[Keoke]

HI Ianh, Is your car RH or LH drive?. Have you tried backing off a bit on the adjuster for that wheel ?---Cheers-Keoke /ubbthreads/images/graemlins/thirsty.gif

 

[catfood]

When you overhauled the cylinder did you get any brake fluid on the shoes. My BN1 exhibited the same symptoms when a cylinder began to weep fluid (barely enough to notice). The cure was a new set of shoes.

 

[bob hughes]

Ian
Just a point, If its anything like the 3000, the cylinder should be free to slide easy on the backplate as the brakes are applied. If there is too much friction there, they may come on all of a sudden when the pressure in the line finally overcomes the friction and the springs may not be strong enough to return every thing back to normal when you release the brake. Does the problem occur when you apply the brakes when already stopped? you could get an assistant to apply the brakes and you observe from underneath, or gently operate brakes with drum off.

/ubbthreads/images/graemlins/cheers.gif /ubbthreads/images/graemlins/england.gif

 

[Dave Russell]

Bob & Ian,
The BN1 rear brakes are not like the later Healey brakes. Instead of a sliding wheel cylinder, there is a "conventional" double ended wheel cylinder that is fixed to the backing plate. A single adjuster/shoe anchor like the later cars. The parking brake is a complex arrangement of a central operating lever, two sliding plates, & two balls, all under a flat holding cover/plate.

The shoes are unsymetrical with partial lining on the leading & trailing shoes. There must be the correct amount of lining & it's placement on the shoes. The shoe return springs are connected shoe to shoe rather than shoe to backing plate.

There is some servo action caused by the leading shoe being able to slide on it's anchor. It is not linked to the trailing shoe.

I can see several places/reasons for the shoes failing to retract. It was a really trouble prone design.

Inner restriction of the rubber hoses due to liner collapse, friction in the sliding abutments, friction in the wheel cylinder pistons, weak retracting springs, friction or binding in the parking brake operating links, Improper lining, it's length, or it's placement, possibly contamination of the lining. No wonder the design was changed on subsequent models. I think the only solution is to carefully check all areas. I realize that you have checked these things but check again.
D

 

[stever]

Dave already mentioned this in the above post, but I want to reinforce it because it turned out to be what was causing some rather interesting rear brake issues with my car: "rubber hoses due to liner collapse". I finally figured out that the flex hose in the center of the car near the pumpkin where the single brake fluid pipe splits to two pipes for the rear wheels was collapsing inside. This was not visually detectable and it was somewhat intermittent in that sometimes the pressure would release and/or pressurize OK with the pedal and at other times not. If it is an old flex pipe/tube you might consider just replacing it as preventive maintenance. Just a thought. HOwever, I have to admit that as your problem is only one wheel this isn't a real likely source of your problem.