Hi everyone, My WM20 has only just passed it's MOT because the brake drums are out of true. I am worried that if i have them skimmed the brake linings will then be undersize causing the cam to overide and lock the brake.I had this problem with my other motorcycle an M72,brake shoes are available for them where the foot of the shoe which is operated by the cam is threaded so you can adjust each shoe height independently (clever russains)I don't believe adjustable shoe's are available for BSA's, maybe oversize linings? Has anyone found a way around this problem?. Thanks Mike.

email (option): michaelggilbert@btinternet.com

Hi Michael,

In order to shorten the brake pedal move and avoid lock,
I asked to renew the brakes with ticker lining.

Usually it would be best to bring to the guy who makes them all 3 part:

Drum, brake hub and shoes.
Then he can adjust all after skimming.

Noam.

email (option): noam10@gmail.com

hi michael,how much run out are you talking about?can you clock it with a dti.ive skimmed loads of break druns and discs in my time i have never seen more than a couple of thou run out,although a couple of thou can make a lot of judder,where are you based? i can skim drums with the wheel and tyre complete
cheers rick

email (option): richardholt@rocketmail.com

Thanks Guys. Rick, i don't know how far it's out,5 graduations on the MOT machine and 5 is the limit.I doubt that it's measured in thou because it is a modern machine.Getting it machined is'nt the problem although he does insist that i remove the tyre.I was rather hopeing to find out if anybody supplies oversized linings.Cheers Mike.

email (option): michaelggilbert@btinternet.com

Hi Michael..The standard internal diameter for both drums is 7.015-7.020" and maximum size after skimming should not exceed 7.040"..so .020" to play with. This allowance is fairly small because the drum thickness is not very great...(0.176").
Martyn Bratby, who reconditions carbs, also does brake shoes and can do oversize linings. However, it is unlikely the material thickness will be correct for the remachined diameter of your hub so these too will need to be machined or hand finished to fit....Ian

email (option): ian@wright52.plus.com

Rick, do you have any experience with skimming detachable drums, and if so, how do you mount them ?

The Brother-in-law and I trashed a Norton drum in an attempt to just clean up the surface. It was mounted on a tight-fitting mandrel but I suspect that it began to 'sing' - that was before the b*stard thing began to cry out in pain though !

Hi Ian, So if i ask the engineer not to exceed 7.040 i should be ok with std linings? and if he has to go larger to true the drum it's had it anyway so there should never be the need for oversize linings at least in theory.

email (option): michaelggilbert@btinternet.com

I usually make a plug that fits in the lathe with a spigot on it that is an exact fit for the hole in the drum, then drill and tap the holes using the drum as a template. You will probably need a titanium nitrided bit on your cutting tool as the surface tends to harden through the heat, this may be why it was "singing" as it was pushed away by a hardened part. Cut a reasonably large cut at first to break through the hardness and more imprortantly if you have back gears on the lathe use them and try to cut it as slow as possible as it's surface speed will still be very fast.

email (option): davmax@ntlworld.com

Hi Michael...Yes, in a sense you are correct. There is a .016" permissible wear limit on the brake shoe linings. (.156" thick standard..minimum .140")...or .032" over the diameter.
So assuming a good drum but with worn brake shoes (close to the limit) you would have more clearance than you would with a remachined drum and new (standard) shoes.
However, assuming you removed .020" from the drum but wanted to maintain the clearances and brake arm/cam positioning of a new hub with new shoes, thicker linings would be required...Ian

email (option): ian@wright52.plus.com