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Drum brake judder

Submitted by michael_harvey on Wed, 04/09/2019
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Heavy Twins

I have a 1957 88 with a Commando TLS front brake. I have fitted a stiffening kit and new brake shoes but suffer tremendous brake judder. I have measured the drum run-out / ovality as 0.04mm and wondered whether or not this is within acceptable limits or not. It does not seem much to me, but I'm more used to car disc brakes than drums. Also, when applying the front brake, the forks seem to twist a bit so the front mudguard moves in relation to the wheel looking from the top, in a clockwise direction. Is this normal? I fitted new fork bushes. Thanks, Mike.

Submitted by david_cooper on Wed, 04/09/2019

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Have you slackened the spindle nut and held the brake lever hard on before tightening it again?

Submitted by david_cooper on Wed, 04/09/2019

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I seem to remember mine was pretty horrible to start with. I put a big chamfer on the shoes (3/4 inch I think) , plus all that business about centralising the cam lift point off the bike. It's good enough to attract surprise and praise at the MOT place last time I took it.

Thanks again. Bigger chamfer coming up! It already had some. Looking at the wear on the shoes, they are only contacting in the central area, as if the radius of the shoes is smaller than the drum. Must measure it! Mike

 

Submitted by lance_crossley on Fri, 06/09/2019

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Michael

I have a Tickle TLS front brake on my 650SS and had the shoes relined by Saftek of Cleckheaton fairly recently - excellent service at a decent price. I've had occasion to remove the front wheel several times since then and could check how well the new linings were bedding in. Like you, initially there seemed to be minimum contact. Following advice I read somewhere, possibly elsewhere on this site, each time I had the wheel out I used a file on the worn areas to encourage bedding in,though obviously don't go too mad doing this. Whilst still not fully bedded in they are improving and I'm hopeful of getting a really good brake before too long. I doubt it will be as good as the twin discs on my Aprilia Falco though. Twin discs which are awesome. I read a report a while back by a former racer who was testing this model and he said he would be happy to race it with the standard set up! No plans to graft this front end on to the 650SS though. At least not until I've completed the bedding in process to see the results of that. (Only joking!)

Thanks Lance, the file sounds like an excellent  idea. When I re-lined the brake, I glued 80 grit paper to the inside of the drum, then rotated the drum to wear the shoes into the drum, but I suppose the thickness of the paper meant that when the paper was removed, the contact patch was not perfect. So I can improve that with careful filing. I'm still wondering about the juddering and ovality and what is the tolerance. I have a  '95 Honda RS125R with a disc front which as you would expect on a pukka GP bike is awsome, and I ran them both at the CRMC event at Mallory Park last wekend, the juddering on the Norton was just awful. I had a Triumph TLS in my last Norton 88 and it was fantastic, progressive, powerful (relitavely), smooth and really pulled up well. Thanks again for your thoughts. Mike

 


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