Rear Drum is singing.

[goathands]

Hi all,

I've had a nagging problem with my rear brake. I cannot seem to get rid of a high pitch squeal from my rear drum when I apply the brake at low speed.

I've taken the wheel off and it seems the pads still have some life.
and I've adjusted the pull rod several times trying to get the proper tension, but the noise always comes back.

It happens at low speed, and varies in pitch depending on the amount of pressure I  put on the brake. It's loud and scares anyone on the curb at an intersection.

The brakes were replaced in November, and I've probably put 2k on the bike since then.  

Can anyone help me troubleshoot what could be wrong.

Thanks,
James

[AlfromNH]

When did the noise first appear? The shoes were replaced in November?

[montmil]

Perhaps try knocking the glaze off the drum using some 200 grit Wet-Dri. Have you applied a very small amount of hi-temp grease to the brake shoe pivot point and the brake cam? Examine the shoes for evidence of full contact with the drum, ie: shiny / no shiny spots.

[Justin B.]

I know on disc brakes a squeal is actually the pads vibrating so it's liable to be the same thing for shoes.  Maybe rough up the "drum" surface inside the wheel with abrasive cloth and lightly scuff the corresponding surfaces on the shoes to remove any "glaze".

[goathands]

When did the noise first appear? The shoes were replaced in November?

The noise appeared after the shoes were replaced, maybe mid December.  

Thanks for the comments, they are very helpful. I'll take a look the condition of the rim interior and the shoe.

[nhmaf]

There were also, IIRC, some rubber blocks used in a kit from BMW to stop the rear springs from vibrating, but I think that they were used on the /6 and /7 models if required.

Mine will often emit a small squeek/peep just as I am coming to a fully stop, but otherwise quiet.   I'd try the suggestions above first - including greasing the pivot point on for the shoes and on the cam.

[Barry]

Take a look at this service bulletin ref' nhmaf's comments on spring vibration.

[Semper Gumby]

+1 what previously said.

Something I learned from working on and riding drum brake BSAs:

When you tighten down the axle on a drum brake wheel, first compress the brake fully so that the brake centers on the axle.  THEN while holding pressure on the rear brake, tighten the axle down.  It may help your singing problem and will definitely help improve your braking.

This may require three hands.  If you lack the required number of hands then try Mitosis.