The performance of a new disc brake is NOT impressive. Within two months, however, you will be amazed by the power and modulation of this disc brake.
Car and motorcycle mechanics talk about 'seating' or 'breaking-in' pads on disc brakes. By this, they mean wearing the new pad until the face of the pad is parallel (more correctly, 'coplanar') with the face of the rotor (or disc). Until new pads are seated, only a corner or edge of the noncompliant pad will be able to make contact with the disc. A new or unseated pad has two problems: (1) reduced braking power and correspondingly longer stopping distance, and (2) more caliper flex caused by uneven contact of the brake pads.
How long does it take to seat a pair of pads? If you use the disc as your primary brake, seating the pads should require no more than 200-400 miles and two readjustments. As you wear-in the pads and readjust the brake (by tightening the pads and NOT the cable) the power and feel of your new brake will improve dramatically.
Typically, the brake's first pad adjustment should be performed after about 100 miles of riding. Some bikes may need the service a little sooner if the captain brakes frequently. Do not proceed until you have adjusted the cable as described in Chapter 3 and understand the overall adjustment and break-in process as described in this chapter.
The Necessary Tool
The only tool needed to adjust the pads is a 2mm Allen wrench. We suggest you use a straight wrench with a screwdriver handle. While an expensive ball-end Allen wrench may be easier to use, its decreased working surface can split the adjusting screw. Because it is possible even with this small wrench to split the adjusting screw, never force the wrench when adjusting the brakes.
The $150 Mistake, and How to Avoid It
To adjust the brake's inboard pad, you will have to insert the Allen wrench between the spokes of the rear wheel to make the adjustment. Most split adjustment screws are the result of spinning the wheel or moving the bike without, first, removing the wrench. We advocate keeping one hand in your pocket while adjusting the inboard pad of your tandem’s disc brake. This way, you won't try to spin the wheel with one hand while holding the wrench with the other.
Each pad is adjusted independently. Please note again that you cannot adjust a pad that has hydraulic pressure forcing it inward. While you can loosen the adjustment screw (turn it counter-clockwise), the pad itself will NOT move away from the rotor, and, if you continue to turn the screw, forcing it past its 'soft stop', you will only succeed in opening the system. The sign that you have done this will be a wet wrench and fluid weeping from the grommet. Bad, very bad. Because it is all-too-easy to do this (inadvertently open the system) while loosening a pad…
1). Do not adjust a pad unless the cable is totally loose.
2). Do not loosen the adjustment screw beyond its soft stop.
The best way to attain proper pad adjustment is to turn the screw clockwise until you feel resistance. The resistance you feel is the pad pressing against the rotor. At this point, turn the wrench counter-clockwise until the pad no longer rubs when the wheel is turning. With a new, unseated pad you may have to back off the adjustment by a half turn. Later, when the pad is seated, or coplanar, one-eighth of a turn is all that will be necessary.
Note: Every Hadley Racing tandem hub has four contact seals that can create significant drag when new. It is easy to mistake this drag for brake drag and consequently over-loosen the pads (compromising performance or the integrity of the system), even though the pads aren't rubbing.
Congratulations! Now you have properly adjusted the brake pads. Once you get good at it, the entire above process can be accomplished in 90 seconds.
Your next step is to properly reset the cable tension. As was explained above (Chapter 3), you should use the blunt end of a BIC pen or pencil to establish the correct cable adjustment.
Notice that we performed an entire brake adjustment without squeezing the brake lever once. Never use the brake lever to determine the adjustment without first loosening the cable, checking the position of the piston, adjusting the brake pads and then reestablishing correct cable tension. Don't be surprised if once you've seated the pads and taken the above steps in the proper order, you can still mash the brake lever all the way to the handlebar. The combination of cable stretch, housing compression and brake lever flex make this possible. However, if by using one finger only you can easily squeeze the lever tightly against the handlebar tape, the only remaining cause for excess lever travel must be air inside the system (air is compressible and hydraulic fluid is not). Removing air from the system is covered in Chapters 6 & 7.
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