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Rear wheel cylinder problem - 850 drum brakes
https://www.ausmini.com/forums/viewtopic.php?f=2&t=88132		 Page 1 of 1
Author:  bruvy2002 [ Sat Dec 27, 2014 2:46 pm ]
Post subject:  Rear wheel cylinder problem - 850 drum brakes
Hi all,

Can anyone offer some advice? I replaced my old leaking rear wheel cylinders about 12 months (800km) ago and last week the rear right cylinder locked in the 'out' position, ie brake full on, locked wheel. No problem I think, these things happen, go get another wheel cylinder, fit it yesterday and then exact same problem today...full locked wheel. If I remove drum and brake pads and give it a good wiggle it will release but hardly need to be doing this on the side of the freeway again! :roll:

BTW... 1964 standard 850 drum brakes.

Thanks
Author:  mini_mad_matt [ Sat Dec 27, 2014 2:53 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
The brake hose may be restricted, allowing pressure through when you apply the brakes but blocking the line from releasing pressure
Author:  bruvy2002 [ Sat Dec 27, 2014 2:59 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Hi Matt,

I'll check that again but I don't think that is the problem. I can remove the cylinder completely and it is still locked out until I wiggle and jiggle it back in. I'm gonna pull one apart completely and have a look.

Thanks
Author:  Morris 1100 [ Sat Dec 27, 2014 3:05 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Is the piston coming out too far and cocking sideways?
Author:  bruvy2002 [ Sat Dec 27, 2014 3:20 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Hi Morris 1100,

yes, exactly. Piston comes out too far and cocks sideways. I think Matt is on to something though (I should know not to doubt the experts). I just pulled the old cylinder apart and it was full of crud and rust particles. I think I should invest in some new brake lines perhaps.
Author:  mickmini [ Sat Dec 27, 2014 3:30 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Oversize drum and undersize linings allowing the cylinder to come out too far?
Author:  Scoop [ Sat Dec 27, 2014 3:33 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Hoses old?
Oversized drums?
Weak old springs?
Author:  Morris 1100 [ Sat Dec 27, 2014 4:48 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
I think mickmini has it right. Oversized drums allowing the pistons to travel too far.

Just fit some correct sized drums. (well, actually measure the existing drums first before spending any money)
Author:  bruvy2002 [ Sat Dec 27, 2014 5:35 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Thanks all. Stepped drums and matching new linings all round, was a real tight fit so certainly not allowing the piston to travel too far. Top adjustment is right in to to allow wheel to turn at all! Hoses all new, really think the problem to be as Matt first said, the rear pipes themselves are all original so tomorrow they are coming off!
Author:  goodie [ Sat Dec 27, 2014 7:06 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
Try undoing all your pipes at their unions , and give them a good clean out with compressed air :idea: .
Author:  9YaTaH [ Sat Dec 27, 2014 8:24 pm ]
Post subject:  Re: Rear wheel cylinder problem - 850 drum brakes
bruvy2002 wrote:
Top adjustment is right in to allow wheel to turn at all!


That's normal, but remember to check the adjustment a couple more times after you have used the brakes enough to knock the high spots or furry bits off the linings :D

[Edit: and it don't hurt to remove the drums each time and clean all the dust out...usually gives a better result]
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