Drum brake shoes - uneven wear?
Guinness - 7/6/10 at 07:48 PM
Oh dear, I've started down the rabbit hole and it's looking deeper and deeper.
I've taken the rear arches off and have discovered the leak from the diff is now more like a flood. So I've ordered a set of diff
seals.....
Anyway I've removed the rear drums to try to get the drive shafts out, and the rear shoes are un-evenly worn.
The front pad is about 3mm and the back one is about 1.5mm?
Can they be adjusted? I thought they were self adjusting? / centring? The cylinders, shoes and drums were all new 7,500 miles / 4 years ago.
Mike
adithorp - 7/6/10 at 08:07 PM
Were they equal thickness when new? Drum breakes often have one brake shoe thicker than the other.
Are the pistons free in both ends of the cylinder? If ones stuck then you'll get uneven wear.
Have you got the leading and trailing shoes the right way around? It's a common mistake.
Having said that drum brakes rarely wear evenly.
"Self adjusting" is in almost every case just a matter of making sure you don't end up with so much play that the pedal goes to the
floor before anything happens (like happened with negected manual adjusted brakes). They really need adjusting manually, either by turning the barrel
nut or clicking up the ratchet (whichever is fitted), to get the best results.
adrian
Xtreme Kermit - 7/6/10 at 08:37 PM
This is perfectly normal with single cylinder drum set-ups.
You have a leading shoe (the front one on the sierra where the cylinder is at the top) and a trailing one.
The leading shoe does more work because of the rotation of the drum adds more braking effort.
The trailing shoe is pushed out at the top against the rotation of the drum, thus is less efficient.
When they had drums on the front, they typically had two cylinders (one top and one bottom) to overcome this effect and make them more efficient.
Don't sweat it - run them 'til the leading shoe is warn down, then replace 
mcerd1 - 8/6/10 at 08:25 AM
quote:
Originally posted by Guinness
Can they be adjusted? I thought they were self adjusting?
as above the wear your getting sounds perfetly normal
they are self adjusting, but in real life a few thousand miles on the road and the most adjusters start to get seized up - so to get the best out of
them you need to adjust them yourself whenever you service the brakes - but they'll still wear the same way....
[Edited on 8/6/2010 by mcerd1]
Guinness - 8/6/10 at 08:52 AM
Ok, thanks guys. I'll give them a clean with some brake cleaner and not worry about it until next time.
Just waiting on the diff seals now......
turbodisplay - 8/6/10 at 08:57 AM
Are you sure the diff breather is not blocked? When it heats up the pressure can force fluid out of the seals.
Darren
Guinness - 8/6/10 at 09:02 AM
quote:
Originally posted by turbodisplay
Are you sure the diff breather is not blocked? When it heats up the pressure can force fluid out of the seals.
Darren
Yup! I first noticed a leak last year, but really didn't have time to fix it. So I took the short breather pipe off, and fitted a longer one,
which reached all the way up to the back of the seats.
So I've spent the last year just sticking a bit more oil in before each blat. The oil always just disappears down the pipe.....
Mike