Hayes bleeding proceedure
While these tips were originally intended for Hayes users, the principles are common to almost
all hydraulic brakes, regardless of brand.
The hayes hydraulic brake system is a fully sealed open system.
This means it automatically adjusts for pad wear and fluid
expansion/contraction due to heat.
The system consists of a lever containing the master cylinder
(MC) & reservoir bladder, a caliper containing two slave pistons
and a line joining the two.
Hayes brakes run on automotive DOT fluid. Only types 3,4 & 5.1
should be used in the hayes system.
DOT 5 is silicone based and should not be used. DOT fluid is
corrosive to paint, many plastics and does terrible things to brake pads.
Make every effort to keep the fluid contained and away from your skin.
To successfully bleed a set of hayes you'll need the following:
A Hayes bleed kit - or -
A 5ml syringe
A short piece of clear hose to connect syringe to caliper nipple
A small phillips head (+) screwdriver
First you must push the brake pads right back. This is best done with
something soft like a plastic tyre lever.
Care must be exercised not to crush the surface of the pads by using
a hard or sharp tool.
Once the pads are pushed back they should be removed to a place safe
from DOT fluid.
Seating the pistons right back in their bores is the only way to ensure
the right amount of
fluid is in the system.
Arrange the lever and caliper so the bleed screw is uppermost and the
line forms an even slope from the caliper up to the lever.
Open the bleed screw and carefully push fluid into the caliper.
fluid from the caliper and push in fluid until all air in the caliper
has been sucked into
the bleed bottle (or syringe).
Now push fluid steadily through the system until no air comes out the
Replace the bleed screw, close the bleed nipple and wash away all
stray DOT fluid
with soapy water.
This method resets Hayes pistons to stop drag and improve lever
Use a plastic tyre lever or other soft tool to push the brake
pads right back.
Replace the wheel, loosen the caliper mounting bolts to allow
the brake to slide
sideways on the mount. Place a card between the rotor and pad
on each side and
pump the lever until contact is made.
While holding the lever snug up the mounting bolts, remove the
the lever and check alignment. Warped rotors can be straightened
by hand tweaking.