Bleeding motorbike brakes /
changing brake fluid
Changing the brake fluid on your motorbike, whether it be the front
or rear, is an easy task to complete.
A brief overview:
With the hydraulic system used on the majority
of disc brakes, the adjustment is automatic.
Even the brake bleeding (expelling any air that
is in the brake system) only needs to be done if by chance air has
entered the system. This can normally occur
if there is a leak in the system, the Brake Fluid Reservoir has
been allowed to drop below the lower limit or a connection has been
loosened or undone.
Looking after your braking system:
Check the Brake Fluid of both the front and rear
reservoirs (if fitted) every time before you start off on your journey.
Regularly check:
- the soundness of all Brake connections
- the Brake hoses for any signs of cuts or abrasions-even
though they are normally armoured
- the Brake calipers, for leaks and to make sure
all pins or clips are in place.
Items you will need to bleed the brakes:
To bleed your Brakes you will need:
- A new tin or bottle of the recommended Brake
Fluid
- A length of transparent hose - that fits tightly
over the Brake Bleed Nipple and will reach the floor.
- Tools to undo the Brake Bleed Nipples and remove
the Brake Reservoir Cap
- And a recepticle to collect the old Brake Fluid
into-preferably a clear jar.
Bleeding the brakes:
Place
the bike on its centre stand (if it has one) or on its side stand
but a Paddock Stand would be ideal to ensure that the Brake Reservoir
is upright
Remove
the Reservoir Cap and take out the rubber Diaphragm that is normally
fitted inside, top up the Reservoir to the Maximium Level and refit
the Diaphragm and the Cap
Remove
the rubber grommet off of the Bleed Nipple on the Brake Caliper
and squeeze the hose onto the Nipple
Pour
between one and two inches of Brake Fluid into your jar and drop
the end of the hose into it
This
will prevent any air being sucked up into the Brake system when
the Bleed Nipple is opened
You will then need to either squeeze the Brake Lever or depress
the Brake Pedal (depending on whether you are doing the front or
the back) hard and whilst maintaining the pressure open the Bleed
Nipple half a turn
As
the Lever or Pedal completes its travel a small amount of Fluid
will be released into the jar
The
Bleed Nipple must then be tightened just as the Lever/Pedal reaches
its stop
When
the Bleed Nipple is tight the Lever/Pedal can be released again
back to its normal position
Repeat
this process-applying pressure,opening Bleed Nipple,let Lever/Pedal
complete its travel,tighten Bleed Nipple,and release Lever/Pedal
This
will be repeated about four or five times before you will have to
remove the Reservoir Cap & Diaphragm and refill the Reservoir
with the new Brake Fluid
This
process must be repeated until Brake Fluid being spent into the
jar is free of any air bubbles
When
this has been achieved the Bleed Nipple must be tightened down properly
Remove
the hose from the Bleed Nipple and replace the rubber grommet
You
have to repeat this procedure for each caliper, so if you are doing
the front you will have to Bleed the calipers on either side of
the Forks
Recheck
the Brake Reservoir and top up if necessary-making sure not to overfill
as when you come to replace the Diaphragm and Cap it might overflow-
and Brake Fluid will eat its way through your paintwork very very
quickly.
You
have now completed the task of Bleeding your Brakes
Changing
The Brake Fluid:
Brake
Fluid is Hygroscopic - absorbs moisture - this moisture can permeate
through the Brake Hoses and contaminate the Brake Fluid
The
water in the system will then heat up under braking and can form
vapour locks which in turn will destroy the effectiveness of the
brakes
So
changing the Brake Fluid at regular intervals will prevent this
happening, and this is also easy to do
It
is the same process as Bleeding the brakes, except that you open
the Bleed Nipple and operate the Brake Lever/Pedal to pump out the
existing old Brake Fluid
A
small amount will be left inside but not enough to make a difference
Top
up the Reservoir with new clean Brake Fluid as continue to operate
the Brake Lever/Pedal until you see the new clean Brake Fluid coming
out of the hose
This
should have flushed out the last bit of old Brake Fluid
Close
the Bleed Nipple and then Bleed the system as described above
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