I've just acquired a nice Mk3 Roadster. I'm having a problem with the rear disc brake binding after a very short run. When cold, the rear wheel moves freely and the brake operates after a little free play movement at the pedal as it should - with a nice firm action. After a very short run, the rear brake will be binding on making the rear wheel very hard to turn at all, the brake light is on constantly and all the free play at the pedal has disappeared. My first assessment was air in the system so I've bled the system a couple of times with little / no further bubbles appearing. I've also flushed the brake fluid through with Dot4 fluid so the fluid is new. My next action is to dismantle the caliper to see if anything is amiss, however I believe that the last owner recently did this and replaced all the seals. Any pointers? It's difficult to raise the caliper above the master cylinder to bleed it thoroughly because of the hose joints being fixed to the mounting bracket. Thanks.
If the brake light is on…
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There are very specific…
There are very specific instructions on how to reset the AP rear brake cylinder up after dismantling to ensure the piston travel is correct. Sounds like they were not followed and the pressure is not being released as the piston is not moving back far enough to open the pressure release port.
http://classicbike.biz/Triumph/Maintenance/LockheedBrakes/Lockheed_Hydraulic_Brakes_Triumph_Norton.pdf
Overhaul Procedure Sheet 114B pages 7/8 contains the rear brake master cylinder adjustment.
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There are very specific.....rear master cylinder overhaul
Thanks - I'll try this out - the previous owner fitted a new master cylinder mounting and so may not have followed the set-up procedure.
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Thanks John. This worked! I…
Thanks John. This worked! I also found that a flat washer had been fitted on the piston end instead of a sprung washer. I think this was stopping the return fluid flow when the pedal is released!
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I had a caliper mounting…
I had a caliper mounting plate that was slighly bent so the caliper was not vertical - the caliper was binding & hot after a short run.
Sounds like your pistons are not retracting after application - looks like a caliper strip to see what's going on.
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Good that it worked, if it…
Good that it worked, if it had not there was no other obvious problems to look at.
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If the brake light is on then there's pressure in the system. So something affecting free movement in the master cylinder or pedal linkage. Start with the pedal, pivot and return spring 'cos that's easy. Then strip master cylinder...