Chapter 6

Preparing to Bleed the Brake

Bleeding the brake, like seating the pads, is a phrase that won't make a lot of sense to non-mechanical types. When someone says they've bled a brake they mean that they have removed all the air from the inside of the hydraulic system. Air in the hydraulic system is very bad because instead of stopping the bike, your hand pressure is being used to make big bubbles small.

Unless you open the system (e.g., open a seal that allows fluid to escape and air to enter), the only time you'll need to bleed the system is after you've changed the fluid. Because brake fluid does degrade over time (which lowers its resistance to boiling), most mechanics will advise you to replace the fluid every two to three years.

Even if you don't yet need to replace the fluid, the process of bleeding the brake requires you to go out and buy brake fluid. Fortunately, the Formula hydraulic system uses ordinary DOT brake fluid-the stuff found in 99.9% of all cars, trucks and motorcycles. For an exasperatingly long explanation of various DOT fluids and their boiling temperatures, you may refer to the next-to-last chapter.

How Tight is Tight?

A problem we've seen crop up from time to time is that a rubber part of the hydraulic system has been broken through over-tightening. While car and motorcycle mechanics long ago learned to "go easy" when tightening hydraulic fittings, most of us have not yet learned the distinction between metal-on-metal and metal-on-rubber tightness. Learning this distinction in feel is especially important when adjusting the pads (in either direction), tightening the bleed valve on the caliper assembly or reinstating the 3mm bleed screw on the remote master cylinder. For these fittings, we recommend "light-bulb-snug" as opposed to "lug-nut-tight." If fluid doesn't seep out when squeezing the brake lever, it's plenty tight.

Necessary Tools

DOT brake fluid

2. Formula Bleed Kit which contains:

-a syringe

-a small clear plastic hose

-a large clear plastic hose

-two brass fittings

-a 6mm white nylon spacer

3. Four Allen wrenches-2, 3, 4, & 5mm

4. An 8 mm box or open-end wrench

5. A flat-blade screwdriver

6. Shop glasses or safety goggles

Which Fluid?

If you need to bleed your bike's brake before tomorrow's ride, it's okay to use D0T 4 brake fluid - which can be found anywhere motor oil is sold. Otherwise, if replacing all the fluid, we recommend searching out DOT 5.1 (Motul is a brand stocked by better motorcycle shops). If you have trouble finding DOT 5.1, contact Santana and we can ship some to you. DO NOT USE "bicycle" brake fluid, mineral oil, or DOT 5 (blue) brake fluid (Chapter 10 explains the salient differences in brake fluids)

Find a Good Spot

Bleeding your brake is best performed in your driveway or a workshop. Because brake fluid is incompatible with good flooring and splattered droplets will soften paint if not cleaned off within a few minutes, this is not a kitchen table operation.

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