howling drum brake

82 550 LTD. Rear Drum brake howls like a SOB when the brake is applied. New shoes installed. It doen't lock up like they do when the glue gets bad, just it howls. The drum appears to be ok...

If the drum is bad, is my only option to find a different rim?

if there is enough material the drum can be turned.
i wonder if the new shoes are "arced"to fit the drum.
in other words sometimes the o.d of the shoes does not correctly match the i.d. of the drums allowing vibrations which cause the noise.
holding the shoe up to the drum and checking if it fits the radius of the drum should tell the story.

leon

When installing new shoes, I sanded the leading edge of the shoes & also sanded the drum very evenly & carefully to remove any glazing. Others had reported squealing from new shoes. Be sure to use the proper lube at the pivot points.

Hmmm...good point martin. I did do a quick pass on the drum, but I didn't spend more than a few mintues on it, and didn't do the new shoes...

blackbanshee- are the shoes identical or should they be installed a certain way? I remember on a mountain bike of mine the pads were adjusted so the leading edge made contact with the rim before the "lagging?" edge. Howled so badly I'd draw less attention to myself by jumping off the bike than using the breaks

i have no experience with the 550's drums,sorry.
i just know from my experience with industrial equipment about the arcing needing to match.
martin brings up a good point about the leading adges of the shoes being beveled sometime as well.do you have a brake rebuilder close?they could probably help you get it straightend out.sorry i am no more help than that.

leon

is there along and short brake shoe or are they both the same?

I'll have to take a look. The bike is still put up for winter. I wanted to say they are the same size/shape.

If one is bigger/longer than the other, which one would go where?

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