tips:
If the linings are too thin (or worn) you can rotate the actuating arm one spline rearwards without much worry. To confirm that the cam won't go over center remove the brake plate and see how far the cam needs to go before it can go over center.
To properly bed in new shoes, line the drum with glue-backed sandpaper (often used for power sanders and the like). Cut strips the needed size and stick them on the drum. Next insert the assembled backing plate, mount the wheel in the bike (or put the axle vertically in a vice) and attach torque arm. While gently rotating the wheel, actuate the brake arm and allow the sandpaper to shape the shoe linings to mate with the drum. Remove the wheel from time to time and observe how the shoes are contacting the sandpaper. Don't over do it.
When installing the wheel in the bike in preparation for riding, install axle, axle nut and pinch bolt but leave everything loose. Now then, with the wheel off the ground, give the wheel a good spin in the normal direction then grab (step on) the brake to bring the wheel to a stop. Now, without releasing the brake, tighten the axles, pinch bolt, etc. The brake drum is now properly centered with the hub.
Do the above correctly and you'll be surprised at how well those old drum brakes work.
CB77 brake cams
CB77 brake camsGood morning Mike
I think I'll end up doing as you suggest. I'm still stumped as to why this issue has materialised and I was concerned that by doing this the rear arm needs to be pulled forward to meet the cable nipple taking the shoes off the "flats". With all that I'll still have to try it. It is suggested that the shoes should have 5mm thick lining but I'm wondering why the brakes don't become ineffective when 1mm is worn off them. The wear limit is 2.5mm!
CB77 brake camsHi Nick in Paradise!
Cheers for your suggestions, especially the final one on centralising the shoes! By coincidence I ought industrial strength double sided tape a couple of weeks ago that will secure the sandpaper against the drum. Moving the brake arms on the splines is the way to go I think however why this has arisen with 4mm re-lined shoes is still a mystery considering that 2:5 is the wear limit!!! I've asked David Silver spares to confirm the material thickness of the OE and aftermarket shoes they are selling. Thanks for your tips and everyone else's; the centralising one will make a difference.
This is great advice. Thanks for posting it.
CB77 brake camsHi to all who replied to my query. I haven't ignored your advise, it's just that I've had a winter virus that's kept me grounded ed all week.
Old geezers/old bikes, susceptible to breakdowns😔 Brake problems.Carl,
You say you have 'advanced' the brake arm on the splines. did you move the end of the arm nearer to the cable nipple or further away from it, in other words did you move the arms clockwise or anti-clockwise in relation to the splined shaft.
CB77 brake camsHi DJM
I haven't moved them yet, I've been housebound since last weekend with a virus thing and feeling very sorry for myself😔! I will move them clockwise and have the cam off the "flat" slightly! In countering the problem I'm still not getting why it has arisen if you get my thinking? Arms on the dots, new cable, 4mm re-lined shoes! OK the originals were 5mm but that shouldn't cause the current problem as the minimum wear limit is 2:5mm. Hopefully this virus thing will go and I'll get at it again. Thanks for your input it's much appreciated. Karl
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