On 14/3/20 7:57 pm, Xeno wrote:
On 14/3/20 6:18 pm, Arlen Holder wrote:
On Sat, 14 Mar 2020 17:04:31 +1100, Xeno wrote:

It tells you what it does in the description. It measures clearance
between the brake lining and the drum.

That doesn't explain how to use it, but that's OK as the way I do the
shoe-to-drum clearance is I adjust that by a friction fit and then
back it
off a few notches, and then I engage the self adjusting mechanism once
it's
all put back together.

BTW, do you radius grind brake shoes when fitting them to an oversized
(worn or machined) drum.

Here is something for you to cogitate on. You have a drum that requires
machining. You do that and it is now *oversize*. You now go out and buy
a set of new shoes. What you will find now is that the diameter of the
shoes no longer matches the diameter of the shoes. When you adjust the

Correction, ..... shoes no longer match the diameter of the drum.

shoes up, as you describe above, the linings only contact the drum in a
small section at the centre of the length of the lining. Both ends of
the lining will not contact the drum. That means that, as you are
bedding in your nice new brakes, only, say, 25% of the linings contact
the drum. Guess what that does to brake efficiency?

There are 3 solutions to this issue.

The first is to radius grind the new shoes so that their arc matches the
arc of the drum. Used one of these radius grinders in the 70s.
https://www.youtube.com/watch?v=afuwxWqBBa8
Just need to be sure the dust extraction and capture system works and it
looks pretty absent on the video.

The second is to replace the drum rather than machining it. In fact, a
lot of manufacturers don't recommend drum machining these days.

The third is to get new shoes with thicker (oversize) linings to match
the larger diameter of the drum.

Some say all linings should be matched to the drum diameter - oversize
or otherwise to ensure an efficient and rapid bed in. Like this one;
https://www.youtube.com/watch?v=WQhnTidoJEM

Anyway, just something more for you to think on.



Luckily, nowadays, very few vehicles I've worked on have drum brakes,
where
that specific drum was on an SUV that went something like 180K miles
on one
set of rear shoes (and there was _still_ meat on those rear shoes but I
replaced them anyway because I didn't want to have to take it apart
again).

It's shocking, actually, how long the rear brake shoes lasted on that
SUV,
where I replaced the clutch twice in the time that I did the shoes just
once, and that rear drum had plenty of meat left for another 180K miles.





--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)