Rear drum brake

Britstuff said:

Hi Mike:

Before I fixed the problem on my bike the rear brake was hopeless and felt just like you describe in your recent reply to @Fast Eddie (Nigel). It was obvious something was not right. After replacing the brake drum the rear brake works as it should, i.e. reasonably effective (for an old brit bike) and (most importantly in my mind) getting better every time I take it out for a spin as the brake shoes are now presumably actually bedding in!

For me, the light bulb moment was discovering that when I rotated the rear wheel, the rear chain / brake drum wobbled slightly from side to side. Oddly enough the rear brake did not pulsate, it was just rubbish.

My new brake drum came from AN, (by way of Coventry spares) and works great.

Does anyone actually turn brake drums anymore? Assuming mine was warped, I was hoping to get mine checked out by a local brake shop. However, everyone I went to looked at me like I was from another planet. Consequently I took the "hail mary" option and bought a new drum, which fortunately fixed the problem. It took further head scratching to later realize that the drum was not warped but the brake drum collar was ever so slightly damaged / deformed.

Cheers,

James

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kommando said:

By now if you take it apart and inspect you should either see witness marks where there are parts touching stopping the shoes from fully moving or on the shoes see how much of their circumference is actually touching the drum from the wear marks. If the wear marks show the shoes are not full mated to the drum then they either need arcing or the hole in the centre of the brakeplate needs opening out to allow the shoes to centralise.

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Arcing with sandpaper is a great idea... but a lot of work. And not always possible without first machining the shoes smaller in a lathe.

But, I've had shoes supplied both too large, and too small a radius.
The suppliers sending bogus shoes is sheer madness.

"Bedding in" is ancient speak cuffing the highs off the linings.
Not relevant to shoes that are not the correct radius to begin with.

concours said:

But, I've had shoes supplied both too large, and too small a radius.
The suppliers sending bogus shoes is sheer madness.

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Taiwan is one of the culprits here, they can use the nearest metric thickness lining so you get a half worn lining straight out of the box. There are others, I get round this by buying shoes with custom linings where you supply the old shoes and the ID of the drum and the OD of the linerless shoes on the backplate. Both Villers and Saftek in the UK supply this service and use the grippy forklift truck linings.

Unlikely to be of much help, but the size of the Norton rear brake is identical to the rear brake of a classic Mini. I use Mini shoes because my brake is converted to hydraulic operation.

Hi Mike,

For my bike, I suspect it will take a long time to bed in the brakes because I have new shoes in the original drum that has likely tens of thousands of miles on it. So the shoes will have to bed in to a drum that has worn to a larger diameter.

But when I first used the new shoes, the rear brake was next to useless. I use it for every stop since I installed and now I would guess it is up to 1/2 its full effectiveness. I can stop the bike with it alone, but not aggressively.

At this point, I cannot lock up the rear wheel. When I can, I know the bedding in will be complete!

I am not doing the sandpaper to bed them in because my AN front master cylinder with reduced bore size is very effective

Dennis

To be honest the rear brakes aren't really design or to be locked up as all that does is skid the back tyre, but the rear brake is used to slow the back wheel down to match your front brake stoppages, your front brake does all the work so having good brakes up front is so important, after 49+ years I am still running the original rear brake shoes although I have replaced the rear drum/sprocket, I have no problem with using my rear brake with my front brake and if I need to can lock up the rear brake if I wanted too but I don't, as I say I use my rear brake as its meant too to slow the back wheel down to match your stopping speed of the front.
I have never on all my bikes as well cars and trucks have I ever needed to lock up my brakes for any reason, I use my brakes to slow down but not over use or abuse them, in fact when riding I very rarely use my brakes up in the tight twisty ranges and only mostly use my brakes for coming to full stops or slowing down when need to.
Using the rear brakes with my front brake as you should the right way the Commando rear drum works well and does what it is supposed to and not abusing my rear drum my brake shoes have out lasted the drum/sprocket, I have never had any problems with alinement of my drum except for once when the circlip mount broke away from my second rear drum it was a cast iron drum not steel and I say it came from India although I got it through my local British bike shop, when it broke the drum moved and was scraping on the brake back plate so I ordered a new drum/sprocket from RGM a steel one, but while waiting for it to arrive I took the broken one to work mounted it on the lathe and cut a new deeper circlip mount and put a larger circlip in, worked a treat and after 14 years it's still on my rear wheel and the new replacement drum and sprocket is still waiting under my work bench with my other parts, when this happened I put up a threat in how I fixed the broken circlip mount the outside edge had broken over 3/4 around the circlip which made the circlip come out of the mount and cause the rear brake to jam, I was about 4 mile from home when it failed but manage to ride home very slowly.
This was such an easy fix 10 mins to set up on the lathe and 5 mins to cut a deeper circlip mount using an internal bar cutter and a 42mm circlip (2 sizes bigger than the original circlip) cost was $2 for the circlip and 15 mins work on the lathe.
Other than that I have never had any problems with my rear drum or alinement problems in 49 years, my Norton was an everyday rider most of its life and has clocked up over 160k mile.
To the OP might be a good idea to check on that circlip mount, could be a problem there.

Ashley

Last week i fitted a Madass rear hub and brake assembly. Did 180 miles saturday. Excellent! No mushy brakes, no rubbish cush drive set up, no broken circlip that tries to hold the bearing in the brake drum. Just fit the wheel, tighten axle, adjust brake and ride. Thank you Don Pender. Graham.