Front brake linings

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Front brake linings

Postby John R » Fri Oct 19, 2018 6:23 pm

Sort of warning and sort of question. When I built my '56 KHK project it came with a good front wheel and the drum surface was smooth and true. Also there were brand new shoes and linings, probably repop, so I used them.

Finished the bike a while back and have put on about 5000 miles, and when doing some maintenance thought I'd clean-out the drums. The front brake had felt good, so stunned when took wheel off and found drum badly scored. The linings, which are black composition with metallic (probably zinc) traces in them must be too hard for the pressed steel drum. I don't have any genuine H-D linings to compare. Any suggestions for good linings? Otherwise I'll have to experiment.

These shoes were mainly used on cast iron drums and maybe the linings would have been fine for those.

Will have to skim the drum and discover how much cut cleans it. As the steel is only about 1/8" thick there's not much to work on!
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Re: Front brake linings

Postby Tim The Grim » Fri Oct 19, 2018 10:39 pm

Not good news...This happened to my ‘54 hub and after it cleaned up there wasn’t enough material to maintain integrity of the assembly and the wheel would not remain true. Shoes were arced to match and new spokes, but all for naught.
I was able to do the machining myself and got kind of freaked out at how thin that area was and how inadequate the design of the hub really was. Maybe get the drum bore flame sprayed and ground back to stock diameter.
For a show item, if you remove more material, you might get away with it but for a rider you’ll want to consider other options.
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Re: Front brake linings

Postby Ferrous_Head » Sat Oct 20, 2018 8:46 pm

Yes, the wrong linings will tear up your drum.

For expert help and opinions speak to these guys. They know exactly what to do.

https://www.vintagebrake.com/
"I know only too well the evil that I propose, but my inclinations get the better of me."
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Re: Front brake linings

Postby John R » Mon Oct 22, 2018 1:29 pm

Thanks for advice guys. I've made some enquiries about flame metal spraying and spoke to one company that specialises in industrial metal spraying, and two old-school restoration companies. None had done this and none liked the idea. The problem they saw was inadequate bonding to the drum as it's nothing like weld, the thinness of the finished metal layer and its likely inabilty to remain intact under the application of brakes. Also the choice of sprayed metal would be problematic and could be too hard or too soft.

I'll try skimming and see how much has to be taken to clean, or nearly clean. Nothing to lose as currently unuseable. If too much I'll have to locate a replacement wheel or hub.

I appreciate your help. John
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Re: Front brake linings

Postby chuckthebeatertruck » Mon Nov 05, 2018 6:39 pm

You might be surprised that not all of those ridges are truly as deep as they appear. A lot of times, the metal gets stretched into the valleys vs. truly worn away. Instead of trying to skim the drums to a perfect surface, try to get it to 75%. If you're within the boundaries of oversized linings, then go to 90%. At that point, we can turn you on to woven linings. You can order them in a variety of widths and thicknesses from industrial supply houses.

Here's the cool part -- the lining wicks heat out FAST so you can get away with a thinner drum and not warp the crap out of it. The woven linings will conform to the drum -- so that 90% surface works pretty darn well.

I know, because I did it after getting turned on to this by Dr. Dick.

Here's a whole write up on woven linings:
http://xlforum.net/forums/showthread.php?t=1974040

I've got well over 5K miles on the latest set -- the wear is just fine and they STOP. They've gotten even better in the last 1000 miles. Couldn't tell you why, but I can tell you I'm happy.
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Re: Front brake linings

Postby John R » Wed Nov 21, 2018 12:27 pm

Thanks Chuck, that gave me hope, and it's all worked out. The wheel was set-up for skimming and showed no belling which can happen if spokes overtensioned, or ovality from uneven spoke tension - can happen when someone trues an untrue rim. The botton line is that an 8thou cut cleaned it. The scoring had looked much worse than that. This steel isn't free cutting so the finish isn't 'photo perfect', but it is good. Feels smooth under thumbnail drag.

Probably ok with standard 3/16" soft linings, but 5mm (9thou more than 3/16") should be better. The thickness of the flange is .135", so guess that's the stock used for the stamping. It looks like the factory skimmed drums as part of the manufacture process bringing drum-wall thickness to about .120" to hit 8.005" on the unskimmed drum I have, and on the skimmed drum it's about .112" and 8.020". I'm confident that's plenty metal left, and hasn't signifcantly weakened it.

For anyone rebuilding a wheel, check the drum and do any skimming after trueing.
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