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Re: Rear Brake Adjustment

Subject: Re: Rear Brake Adjustment
From: (Denise Thorpe)
Date: Wed, 6 Mar 96 15:05:47 PST
Ross asked:

> Also, in case this matters, when I loosen the bolt... the wheel will spin
> freely, if I loosen it a tad more, the brakes start to catch, a little more
> and they are free again, a little more and the brakes barely catch, a little
> more freely and and little more they catch again????  Weird...
> Ross (66 MGB)

I had trouble with this too the first time I adjusted the brakes.  I may 
have been a professional mechanic, but I didn't grow up in the garage 
like the guys I worked with.  They had a genetic predisposition to 
understand how a brake adjuster works, I had to look at it.

Here's the scoop:  Both ends of the brake adjuster are square, but the 
end on the inside is also tapered making it pyramid shaped.  When this 
thing is screwed in, a wider part of the pyramid is pushing against the 
tapered blocks that are between the tops of the two brake shoes.  This 
forces the brake shoes apart compensating for wear of the brake shoes.  
The reason it tightens and loosens when the adjuster is turned is that 
the pyramid end of the adjuster is sometimes on an edge instead of the 
flat making it bigger across until it's turned onto the flat again.

The spec is to adjust the brakes out (adjuster in) until the wheel 
doesn't turn at all and then back off the adjustment two turns.  "Two 
turns" really means two flats which is actually half of a turn.  I was 
really annoyed when I found this out.  Why couldn't they _say_ two 
flats?  Then I would have known what they meant.

So, the trick is to find a flat spot on the adjuster and then only 
adjust in increments of single flat spots.  A flat spot is where the 
brakes get tighter when the adjuster is turned either direction.  It's 
better to use a wrench than a ratchet because then you can change 
directions easily.  The ease of turning the wheel only matters on flat 
spots.  Once you've got a flat spot, keep turning the wheel while 
screwing in the adjuster.  The wheel will get harder to turn and then 
easier (as you've discovered).  The easier spot is the next flat.  Keep 
turning in the adjuster while turning the wheel until the wheel won't 
turn even on a flat spot.  Just before this point, the adjuster gets 
very difficult to turn past the high points.  Once the wheel no longer 
turns, back the adjuster back out past one flat spot to the next.  The 
brakes will definitely drag at this point, but this is the correct 

BTW, my single-user brake bleeding equipment consists of whatever empty 
jar is handy and the vacuum advance line.  I put a wrench over the bleed 
nipple, slip the vacuum line over the nipple, crack open the nipple, 
stick the other end of the line in the bottle (not necessary, but less 
messy) and pump the pedal five or six times.  Then I leisurely saunter 
over to the wheel and close the nipple.  It usually only takes one pass 
at this after replacing a wheel cylinder, but that's because I stick the 
point of a pencil in the brake line to keep the fluid from running out 
while the wheel cylinder is off.  Don't use your personalized pencils 
for this because it takes the paint off of them.

Denise Thorpe

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