Chapter 2

The Adjustment Process

Before adjusting your brake, take the time to read this chapter thoroughly. This brake is quite unlike other cable or hydraulic disc brakes used on bicycles, and it requires that you follow the adjustment directions step by step. Skipping a step or reversing the order of two steps is likely to result in a poor braking.

Perhaps the most difficult feature of this brake to understand is how the cable actuates the piston that pressurizes the fluid to cause the braking. While in most brakes the cable itself pulls on the brake, in the Santana/ Formula brake, the cable is solidly anchored within the remote master cylinder and does not pull anything. Instead, pulling the brake lever forces the brake cable housing down the fixed length of cable, causing it to depress the piston hidden inside the master cylinder. This approach (pushing a piece of housing instead of pulling the cable), while counterintuitive, is supremely efficient. Once you can visualize the relationship, adjustment becomes quite simple.

As the pads seat and wear they will need to be advanced closer to the rotor. While a bicycle rim brake may sit a few millimeters away from the rim, the clearance between the pad and the rotor of a disc brake will be a few hundredths of a millimeter. In making such a precise adjustment an essential first step is to be sure that there is no hydraulic pressure pushing against the backside of the pad. The easiest way to be certain of this is to loosen the cable all the way.

There are two barrel adjusters that can be used to either tighten or loosen the cable. The first is an inline adjuster mounted 3-4 inches above the frame-mounted master cylinder. The second is at the top of the master cylinder itself. To loosen the inline adjuster, turn it counterclockwise (looking from above) until the chrome, cable-housing ferrule recedes into the barrel adjuster. The second barrel adjuster is at the top of the pump; to expose it, pull back the dome- shaped, black rubber boot to expose the red-anodized dome-shaped adjuster and adjacent, red, knurled lock ring. Twist the two red-anodized pieces apart from each other, and then, while holding the underlying silver-colored plunger with the thumb and forefinger of your right hand (to prevent it from rotating), use your left hand to twist first the knurled, red lock ring to the base of the plunger's threads. Next, tighten the red dome piece up against the lock ring. When the two red pieces are tightened against each other with no threads showing on the silver plunger, the cable will be slack enough to allow you to perform the next step.

At this point dislodge the black rubber boot at the top of the master cylinder housing (the boot furthest from the headset), and draw it up to the red lock ring.

Now it is possible-without tools-to pinch the plunger mechanism and draw it away from the pump body creating a 2mm gap. Looking into the gap one should be able to see the backside of the piston. Unless there is a problem the upper edge of the piston should be even with the top of the master cylinder housing. If you see something and aren't quite sure it is the backside of the piston, use the plunger to push against it. If the piece can be pushed inward and then pops back into position (there is a spring on the other side), it is, in fact, the piston-the main working part of the entire mechanism.

If nothing is visible and the plunger moves into the pump body three or more millimeters before touching anything, a vacuum has formed on the face of the piston which prevents proper operation. A system in this condition is said to be "in vacuum." Because a system in vacuum cannot be adjusted, normal operation of the brake is not possible until the problem is solved (see Chapter 9). Fortunately, 99% of the time you will be able to see the backside of the piston, and can, therefore, proceed to the next chapter - adjusting the cable.

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