Binding brakes. :-(

My Fiance's Diversion failed it's MOT on binding front brakes.

So, took the callipers off the forks leaving the hoses connected.
Whipped the pads out and pumped the pistons out a fair way. That was
enough access to clean the pistons up in situ with a dry cloth which
seemed to get them pretty shiney. After this they didn’t seem to be
binding but I didn't really check as that's always been enough before.
I could push the pistons back into the calliper and pump them out ok.

As I wheeled it out of the Garage for re-test this morning they were
certainly binding again. Put the bike back in the garage un-retested.

Given I'm reluctant to do a complete overhaul what's the FOAK's advice
on perfect non-binding brake?

 

IIRC there was something in the Haynes manual about lubing the pistons
on Diversions with something (could be Copaslip) because they were
liable to binding. But it could be the product of a duff memory so
take this advice with as much of a pinch of salt as you feel it
deserves.

 

I've got a vague recollection that in the past I've used brake fluid
on the pistons as a cleaner. I think it would also lube their travel
over the dust seals a bit.

Can someone confirm that the master cylinder is not a likely candidate
and cleaning the pistons is highly likely to sort it out?

 

DON'T use Copaslip - it can make rubber things swell and make it worse.

Unlikely to be the master cylinder.

The problem is likely to be caused by corrosion crud build up behind the
piston seals. It does need a total strip, remove the seals, clean out
with a dremel brush and then put it all back together. No need for new
seals ime - they seem to last a long time.

 

Dunno about how likely it was, but I've had a master cylinder
return hole get plugged by old crudded up fluid, which nearly
locked the front caliper solid as it heated up. In my defence
it was on the way home from picking up the SOB. Check the
reservoir and poke a soft wire through the return port.

 

Simon Wilson escribió:

When I was a car mechanic, it was standard practice to spread the stuff over
just about everything.

Copaslip and WD40 - all anyone needs for anything. Oh, and maybe oxy-
acetylene.

 

Thanks to all, I think I'll give the pistons a good clean with brake
fluid in the hope that lubricates and gets every speck off.

 

And gaffrer tape. Don't forget gaffer tape.

Cue "if it moves and it shouldn't, Gaffer tape. If it doesn't and it
should WD40"

cheers

Spanners

 

Cable ties, don't forget cable ties. "If you see one, snip it".

 

Dangerous game.

--
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#www.cuore-sportivo.co.uk

 

Nah, I snip cable ties before breakfast and it's never done me any
har-aarrr-aaarrr-aaaarrrrgggghhh-NO, PIP GERROFF!

 

What's the worst that can happen?

http://petrolcan.me.uk/ukrm/dead.jpg

 

petrolcan escribió:

Snip the tails off, not the actual ties.

 

Where's the fun in that?

 

Get a nice spray of brake cleaner. Pump the pistons out as far as you can
without dislodging the seals and use the cleaner (and a soft brush) to get
everything really clean. Then use red brake grease around the seals,
pistons and the inside of the dust seal (if it has one).

Make sure the brake fluid is clean and fresh. It's good to pump the pistons
out and lever them right back in again a few times (once lubed). It doesn't
do any harm to pump them out again, loosen the bleed nipples and cycle fluid
by levering the piston in again.

If that doesn't work then it's down to stripping the calipers and master
cylinder I'm afraid. If you go that far then just renew all the seals.

 

Order a genuine seal kit for the caliper (£17 from Wemoto) and overhaul
it. Both my Diversions have needed this doing as they seem to just
attract the grot. I tried cleaning and pumping pistons in and out but
this only worked for a short while.

The genuine seal kit also includes the red rubber grease which is used
to fit the seals and pistons.

 

Pah, Copaslip's so passe.

Aluminium zeta grease is where it's at nowadays ..

Paul.

 

Correct.

Use the proper brake seal "red grease" - if you have trouble getting it try
vintage car dealers/spares stockist.

If you still can't get any get a tube of silicon grease from Maplin or other
electronic component stockist.

 

There's plenty of it for sale on ebay

http://shop.ebay.co.uk/i.html?_nkw=red+rubber+grease+&_cqr=true&_nkwusc=
red+rubber+greease&_rdc=1


--
Lozzo
Versys 650 Inter-Continental Hyperbolistic Missile , CBR600F-W racebike
in the making, TS250C, RD400F (somewhere)
BMW E46 318iSE (it's a car, not one of those 2-wheeled pieces of shite
they churn out)