The Greasy Wrench
Bleeding Hayes Disk Brakes

Time: about 1 hour per side Skill Level: moderate What you will need: - 4mm & 5mm Allen wrenchs - 6mm & 8mm wrenchs - 10mm box wrench - Needle nose pliers - Torque Wrench (inch lbs) - Bicycle Repair Stand - Latex (Nitrile) Gloves (dot brake fluid is very caustic!) - Rubbing Alcohol - Clean Rags - 2 spokes - Duct tape - Hayes Bleed kit - Service Instructions from: http://www.hayesdiscbrake.com/tech.cfm - Patience!

STEP 2: Removing pads

To fully understand the procedure of properly and successfully bleeding Hayes brakes, I cannot stress the importance of having good mechanical ability and reading the Hayes Service Manual thoroughly. I have been installing and repairing Hayes brakes since they evolved on the mountain bike scene back in late 1997. Through trial and thankfully minimal error, I have developed a system that is easy and fast to achieve proper brake performance.

1. Remove the wheel

2. Remove the brake pads. Doing so will ensure that the pads will not become contaminated with brake fluid. Using needle nose pliers, pull down on the pad tabs, pulling the pads out of the caliper.

3. Remove you brake caliper from frame or fork. Using a 10 mm box wrench, push the caliper pistons back into the caliper bores. (USE CAUTION!! pushing on the piston shaft will bend the post and not allow the pads to be reinstalled into the caliper with out major caliper service and piston replacement).

4. Position the bike in your repair stand so the caliper bleed screw is perpendicular to the ground. Position the brake lever vertically.

STEP 5: Lever bleed

5. Bleed kit assembly: A Hayes bleed kit is in my humble opinion the way to go....it has all you need: filler bottle, hoses, proper bleed fittings, and brake fluid. Start by filling your filler bottle full of brake fluid, install bottle cap and hose. You will need a fluid catch bottle at the lever. Create a hook for your catch bottle with a couple of old spokes or a coat hanger. Using duct tape to attach the hook to your catch bottle, install the proper bleed fitting onto a section of hose. (HFX-mag brakes use a clear plastic nipple that attaches to the hose and brake lever. The HFX-9 brakes use a small aluminum nipple that install on the hose and the lever). Bend the spoke or coat hanger so that it will allow the catch bottle to hang off your brake lever. Remove the lever bleed screw or plastic cover and install the proper bleed fitting on the lever running the hose into your catch bottle.

6. Remove the rubber bleed screw cover from the caliper bleed screw and install your filler bottle with hose onto the screw. Push fluid down into the hose to insure that their is no air that will be pushed through the system. Tap the hose to allow any air to be pushed upward into your filler bottle. Once there is no air in your filler hose, then you can begin to bleed the system.

7. Open the caliper bleed screw 1/2 a turn while squeezing the filler bottle and pushing fluid into the system. Watch the fluid coming out of your hose attached to the brake lever. You will see air bubbles coming out. Lightly tap your brake hose from caliper to lever with a wrench to force any air to be pushed out of the system. Squeeze your filler bottle firmly for a 5 second count. Repeat until you see only fluid exiting the hose at the brake lever. Close your caliper bleed screw. Torque to seal only!! The caliper bleed screw requires a 2 inch pound torque...It is very easy to damage your caliper by over tightening the bleed screw. It may take a couple of shots of fluid to fully bleed the system. As you run out of fluid in your filler bottle simply close your bleed screw and re-fill your bottle with fluid. Repeat the process.

STEP 8: Rear bleed

8. Remove your catch hose from the brake lever and reinstall the bleed screw or plastic cap into the brake lever.

9. Clean any excess fluid up from the caliper and lever with rubbing alcohol and a rag.

10. Install you brake pads using caution not to bend the piston posts.

11. Put your wheel back on your bike. The lever's master cylinder will need to pump fluid into the system and push the pads properly against the rotor. Centering the caliper over the rotor may be necessary since the pistons were pushed back into their bores. Torque caliper bolts and brake lever bolts to Hayes specs

This is a general method for bleeding Hayes brakes using the Hayes specific instructions. Many of you may be familiar with this and have developed or adapted other techniques for this process. Visit your Local Professional Bike Shop if you are not sure how to properly repair your brake system. Hayes does not warranty any of their products if they have been installed improperly or repaired incorrectly.