mikec
Junior Member
Posts: 60
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Post by mikec on Apr 29, 2008 7:07:29 GMT -5
Hi Guys,
I was just wondering if someone could help with a small problem
I am having with the rear drum break on my 1980 SR.
The problem occurs when I apply the foot pedal firmly but not enough to lock up the rear wheel, there is a loud clunk from the
back wheel and sometimes a chirp from the back tyre.
This does not happen when the pedal is just pressed gently.
I have had the back wheel off a couple of times and cannot see
what the problem is.
Any ideas?
Cheers, Mike.
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Post by joneill4 on Apr 29, 2008 9:25:13 GMT -5
I'm not sure about drum brakes, but my caliper is supported with a rod. The rod on mine is a little egged out, so it clunks when I hit the brakes. If you have a center-stand and a friend (I realize they are hard to come by when you are trying to work on your bike) try rocking the tire while he or she holds the brake.
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mikec
Junior Member
Posts: 60
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Post by mikec on Apr 29, 2008 21:05:21 GMT -5
Hi, thanks for the suggestion, I'll give it a try.
Cheers, Mike.
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mikec
Junior Member
Posts: 60
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Post by mikec on Apr 30, 2008 2:53:48 GMT -5
Hi, I tried as suggested, and am none the wiser.
The rod that holds the drum seems quite firm, with hardly any movement.
There is still a clunk when pedal is pushed firmly but not when pushed gently to start.
It doesn't happen every time. It doesn't happen if you spin the wheel in a backwards
direction.
It's got me stumped, I guess I'll just have to take it apart again and have another look
at the internals.
Cheers, Mike.
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Post by StewRoss on Apr 30, 2008 4:40:22 GMT -5
Make sure you aren't nearing the wear limit on the brake shoes...you don't want it to lock on! See if there is excessive wear on the brake cam shaft to backing plate area as well. SR  |
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mikec
Junior Member
Posts: 60
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Post by mikec on Apr 30, 2008 6:42:54 GMT -5
Thanks Stew,
I'll check those things out when I get the back wheel off.
Do you know what the pad thickness should be?
Mikec.
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Post by fenz on Apr 30, 2008 15:46:10 GMT -5
One more thing to check while you are poking around down there is for wear in the brake shoe backing plate where the axle goes through.
I had a problem with mine being worn and it allowed the backing plate to twist slightly when brakes were applied.
This would make my brake try and stick on for a bit.
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Post by StewRoss on May 1, 2008 1:57:31 GMT -5
Hi, Manual says 2mm lining thickness minimum on the brake shoes...there is a little rubber plug in a window in the backing plate for checking these...but it's only for a quick check. Better really to remove the wheel and check them properly. SR |
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mikec
Junior Member
Posts: 60
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Post by mikec on May 7, 2008 7:00:23 GMT -5
Thanks for your feedback boys,
I think I have the solution.
I think the problem was to do with the angle between the brake activation rod and the leaver
attached to the cam on the drum.
If the angle extends to greater than 90deg I think the rod and leaver can lock in position!
I have had the brake part and cleaned it all up re greased the bits that need it and reset the
arm on the cam all it needs now is rigorous testing...
Cheers, Mike
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Post by solo2racr on May 7, 2008 11:01:39 GMT -5
With 5 years working in a bike shop back in the day, that would be a new one on me. But, I can say that I have seen stranger things.
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mikec
Junior Member
Posts: 60
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Post by mikec on May 8, 2008 1:07:03 GMT -5
Thanks guys,
I have tested the brake and all seems well, it is now working as expected!
Changing the angle of the arm and cleaning and lubricating all parts that needed to be,
has fixed the problem.
Cheers, Mike.
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