The Hayes Users Group   The Hayes Users Group
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 basics

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.

Necessary Equipment

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
Several rags
A small phillips head (+) screwdriver

The Proceedure

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. Alternately suck 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 bleed screw. Replace the bleed screw, close the bleed nipple and wash away all stray DOT fluid with soapy water.

Reseting Pistons

This method resets Hayes pistons to stop drag and improve lever feel.
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 cards, pump the lever and check alignment. Warped rotors can be straightened by hand tweaking.

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