Spent part of the weekend doing the post winter service on
STarduST. Now
nearly two years old and 35K+ miles.
The winter has played havoc with the brakes and I was experiencing
brake
seizing problems nearly every morning on departure for work.
Incidentally the quick fix is to hit the outside of the caliper
fairly
firmly with a gloved hand, this usually frees the pistons
sufficient that
they stop dragging on the rotors; for the rest of the day at least
:-(
Anyways lovely weather last weekend so I decided to tackle the
brakes and
balance the carbs. As the pistons will have to come out of the
calipers
for service I always replace the seals at that time. Past
experience
suggests that this is a bi annual job if you ride through the
winter on
salt laden roads.
Here s my brake piston seal replacement routine for those who may
be
interested:
Front - left side
1. Using 12mm spanner slightly loosen hydraulic union at
caliper, then just
pinch it up enough to prevent leakage.
2. Remove brake pads
3. Remove two caliper retaining bolts
4. Lift caliper assembly clear of rotor
5. Place wooden batten 1/4 to 3/8 inch thick in space where
brake shoes
belong and pump on brake lever . The idea is to get the
piston as far out
of the cylinders as is possible without actually letting
then come out. The
wood batten is to prevent them coming right out. Leave
the batten in place.
Right side.
6. Same thing with hydraulic union as for left side
7. Remove brake pads
8. Remove two allen head bolts which retain caliper and anti
dive lever.
9. Lift caliper clear of rotor and pump the pistons out
against another
wooden batten.
10. Disconnect hydraulic hoses from caliper and wrap end in
something to
stop them dripping all over your tyres.
Disconnect hydraulic hose from left side caliper. Wrap end of
hose.
Seperate calipers from caliper carriers. They just slide apart.
Drain hydraulic fluid from caliper assemblies into a container.
Remove the wooden batten and gently ease the pistons the rest of
the way
out of the brake cylinders. If the pistons won t come out easily -
like
mine wouldn t - then the ideal way to get them out is to use an
air line to
apply pressure through the hyd union and blow them out. If you don
t
have this luxury then this is what I did - I gripped the piston
firmly,
using a pair of pliers with the jaws padded with nylon webbing
strap to
prevent scratching the outer surface of the piston, and firmly
eased them
out. Mine were so corroded that I had to grip the plier handles in
a
vice and pull firmly on the caliper body applying a very slight
twisting
motion at the same time.
Scream all you like - it worked and there were no scratches.
Clean the pistons. Use no abrasive cleaners as these may damage
the hard
plated surface - gold tinge I think it s cadmium. I use methylated
spirit
to clean all brake parts.
Remove the two seals from within each brake cylinder. Scream again
as I
tell you I use a very fine flat headed screwdriver which I insert
into the
edge of the groove holding the seals, then just lever the seal
clear of the
groove then push it out with a finger.
Clean calipers paying particular attention to the lip of the brake
cylinder
bore and to the grooves which retain the seals. My experience has
been
that salt has corroded the alloy in these places such that the
corrosion
has caused the pistons to stick in the bores. Corrosion may be
found in
the seal grooves which if not removed (carefully) means the seal
will not
seat correctly which also binds the piston. I use a toothbrush and
methylated spirit to get into the grooves and judicious use of a
stanley
knife blade and very sharp flat bladed screwdriver to remove
really
stubborn salt corrosion.
When done, clean all the crap out of the bores and calipers. Then
rinse
them out with clean meths.
Pop the pistons into the bores and check they slide
absolutely freely.
Insert new seals which you first dip in clean hydraulic fluid.
Make sure
they are seated correctly in the grooves.
Reinsert the pistons which you have also dipped in clean hydraulic
fluid.
Again check that they slide easily.
Renew grease in the bores for the caliper slider pins. Silicone is
recommended - I used moly grease - my dealer uses copperslip he
says!
Put caliper carriers and calipers back together and check that the
sliding
action is nice and smooth.
Repeat for other side.
Put caliper assemblies back onto forks, torque up bolts, allen
bolts,
reinstall pads, reattach hydraulic hoses.
Now if someone has a neat way to do the next bit let me know.
Remove cover from front brake hyd reservoir, add new fluid to top,
attach
clear poly pipe to right side bleed valve, end in milk bottle
containing 1"
of fluid. Open bleed valve and pump brake lever. and pump, and
pump and
pump and etc. Keep topping up fluid reservoir as required.
Eventually you will expell most of the air from the system and
fluid will
pass through quickly enough that you can properly finish bleeding
the
system. When right side passes fluid with no air bubbles close
bleed valve
and do the left side. There should be very little air left in that
side by
this time.
Finally replace reservoir seals and cap and check brake action
before you
go ride.
The procedure for the rear brake is the same except that you need
to remove
the rear axle, though not the wheel, to get the caliper carriers
and
calipers clear. The rear brake is also MUCH much simpler to bleed.
Regards,
===========================================
Kerry M. Walsh. STOC 116, Pan Clan 338, Paneuro 001
http://www.cableinet.co.uk/users/kwalsh/leather.html
http://www.cableinet.co.uk/users/kwalsh/pan-clan/
STarduST - Gloucester, England
===========================================