Chapter 3

How to Check and Adjust Cable Tension

It only takes sixty-seconds with the aid of a quarter and a BIC pen to verify proper cable tension. While the brake pads and the hydraulic system will not need frequent adjustment, we do recommend checking the cable adjustment before every major ride, or any time the brake does not seem to be performing property. It is NOT that this brake is finicky or comes out of adjustment, but it has been our experience that well meaning enthusiasts fascinated by this cool looking brake will invariably squeeze the lever and decide that the cable is a bit too loose. Half of these people will help you out by tightening the cable's barrel adjuster. They'll walk away satisfied that they've done you a big favor. This seems to happen whenever you park your bike and then turn your back for as little as thirty seconds. It is most likely to happen when your bike is in or near a bike shop. While the cable that operates this brake cannot possibly tighten itself, many enthusiasts have become dismayed at how often the cable needs to be loosened. What follows is the 60-second method for optimizing cable tension and averting 95% of the problems that can occur with a cable-hydraulic disc brake.

Use a quarter or key to remove the slotted vent screw at the top of the remote master cylinder.

2) Press down on the master cylinder float with the blunt end of a BIC pen or pencil.

3) If the float doesn't move, the cable is too tight.

4) If the float does move, the brake will be applied by pressing the float downward. Verify the braking effect by rolling the bike back and forth.

5) Repeatedly let up on the pen, tighten the cable a half turn and then push down on the pen until the over tight cable prevents this method of brake application - the cable is now too tight.

6) Loosen the cable just enough (usually a half turn) to restore float movement-the cable is now perfectly adjusted!

7) As a final check, depress the float one last time to make sure the passageway between the fluid expansion chamber and the remainder of the hydraulic system is not blocked. Blockage of this passageway is the first step leading to system failure.

And now you understand the unique challenge of this system. Bike mechanics and enthusiasts accustomed to adjusting a brake according to lever feel will automatically over tighten the cable of this hydraulic brake every single time.

Anything else on a bicycle that gets misadjusted, i.e., rim brakes or indexed shifting, causes an immediate problem. This brake requires a new way of thinking. An improper adjustment might not emerge as a problem for weeks. But if the cable is even a quarter turn too tight, the very first time the brake fluid is heated (which can happen for a variety of reasons including a lightly rubbing rotor, braking on a long or steep descent, sitting in a hot environment or simply by being parked in direct sunshine), the too-tight cable prevents expanding brake fluid from reaching the expansion chamber. Instead, expanding brake fluid will push the pads inward and cause the brake to rub or worse, lock up. More than one customer has returned to a bike sitting in the sunshine and found a locked brake. The culprit is an over-tightened cable or a depressed brake lever, which prevents warm expanded brake fluid from reaching the expansion chamber.

While a misadjusted cable will, to most people, make this disc brake feel better (because the lever feels firmer), blocking the passageway between the reservoir and the rest of the system 'chokes" the entire system. Sooner or later the choked system will overheat and fail. Fortunately, the experience is not a loss of braking, but is, in fact, the opposite - a sticking brake that refuses to release. When faced with a brake that rubs or a pad that won't release, or a tandem that won't move, many dozens of frustrated enthusiasts (often with the help of a self-stated expert) have - by loosening a pad, hydraulic line, bleed port or valve - instantaneously destroyed the integrity of their hydraulic system. Ouch!

The mysterious onset of brake rub or lock up is a sure sign of only one thing: someone somehow over-tightened the cable, possibly weeks or months earlier.

The only way to restore proper operation is to loosen the cable enough to allow hot fluid to reach the expansion chamber. As soon as the cable is loosened (and the piston within the master cylinder is allowed to retract) the fluid that was causing the brake to rub will instantly find its way past the face of the retracted piston that was blocking the path to the reservoir.

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