Rear brake imbalance

Archives of Posts to the NZ MX5 List back in 2001
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DOUG-BARB

Rear brake imbalance

Post by DOUG-BARB » Sat Jul 21, 2001 4:30 pm

We had trouble get a warrant for our mx5 .because of right hand brake not
working,so I removed the caliper after checking and adjusting every thing
still no go ,so I took it to a brake specialist and they found rust in the
bore of the handbrake cylinder it had to be resleaved at quite a cost and he
said they get 2or 3 Mazda callipers in a week with this problem
Doug & Barb
06-327 7440

simple
Why yes, actually I do run this site.
Why yes, actually I do run this site.
Posts: 129
Joined: Mon May 01, 2006 5:19 pm

Rear brake imbalance

Post by simple » Sat Jul 21, 2001 7:40 pm

I spent quite some time on Thursday with the car up on stands,
cleaning/adjusting/fiddling with the handbrake adjustments. Nothing
achieved, even when I tried deliberately setting the left handbrake
adjuster (on the caliper) to be 'tighter' than the right.

I also removed the handbrake cables from the calipers (easy to do without
any 'scary' disassembly) & checked that they were both free in their
sleeves - no problem there. The equaliser (where the handbrake cable
splits into two - one for each side) is fine. It just seems that there is
something different about the left caliper.

The handbrake imbalance is obvious with the wheels off the ground - one
click of the handbrake pretty much locks up the right brake rotor (against
hand force) whilst the left is still free turning. Takes about 4 clicks to
get the left to bind, & even on full handbrake I can still turn the left
rotor by hand. I'm glad I haven't parked on any steep hills lately! In
future I will add 'try turning wheel by hand' to the list of things to do
when maintaining brakes.

Normally I do brake maintenance every 6 months or so. In particular, the
caliper slider pins need attention - the lubrication on the pins tends to
disappear, presumably washed away. That may be in part because I've not
been using an ideal lubricant - I need to get some good high temperature
grease.

The car is booked into Sterling Clutch & Brake on Monday morning - I
imagine they will be able to establish what's wrong fairly quickly. I'll
find out all I can while I'm there & pass on any useful information.

Karl.


[...]

simple
Why yes, actually I do run this site.
Why yes, actually I do run this site.
Posts: 129
Joined: Mon May 01, 2006 5:19 pm

Rear brake imbalance

Post by simple » Mon Jul 23, 2001 11:10 pm

I took the car to Sterling Brake & Clutch today (or Sterling Clutch &
Brake, depending on which of their signs you look at). Nothing 'broken'
was found. Conclusion seems to be that the pads were making imperfect
contact with the rotor, & calipers were binding on the slider pins due to
the lubricant drying out.

They skimmed the rear rotors & re-faced the pads, cleaned and lubed the
slider pins, reassembled & tested. The assessment took about 15 minutes,
and the repair took under an hour (including taking the car to the local
WOF station to check out the braking left-right balance). Total cost $115
+ GST.

In re-assembly, they also lubricated the little slots in the end of the
pads where they bear on the stainless inserts (which fit onto the caliper
frame). I had never lubricated them before, in fear of getting grease too
close to the rotor - in the past I'd normally just polished the stainless
inserts. Grease on rotors is a bad thing :-)

Sterling B&C also sold me a pot of "Caltex Jet-Lube Kopr-Kote Grease" -
this is an "anti-seize compound" which "provides protection against metal
to metal contact under the most adverse conditions of temperature and
corrosion". "Contains copper, graphite, anti-wear and extreme pressure
additives". Cost $19 + GST for 500g, which should last me quite a few
years. They recommended re-lubing sliders every 12 months.

I had been using Molykote whilst looking for something better. The
molykote is also a copper based lube, but it seems to 'dry out' pretty
quickly. I was unhappy with the dryness after only a month on the car. I
had expected that the large forces involved in braking would have overcome
the small amount of binding I could feel - apparently not.

Overall, I could have solved the problem more cheaply if I had known what
lube to use or had been more persistent, but working on cars isn't really
my thing - I just do it because I'm cheap :-) My car has now passed WOF,
so I'm happy.


Karl.


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