How about stripped (or semi-stripped) threads on one of the parts
of the adjustment mechanism?  That might explain the problem.

On Thu, 4 Dec 1997, Erik Rhodes wrote:

> I think I know how brakes work but can't fathom what's causing this, so
> I must not know enough...
>
> On my '79 westie, the left rear brakes need to be adjusted every three
> weeks, no exaggeration.  I adjust them up, nice and tight, and then,
> little by little over the weeks, they get worse and worse.  Crawl back
> under and adjust again, the left rear has loosened up.  I tighten it,
> feels great, about three weeks later I need to do it again.
>
> What in the world is going on?  I've done this four times already.  Only
> think I can guess is that the adjusting starts are loosening up from
> vibration, but why?
>

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Tom Young               young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA  94549    '81 Vanagon
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