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Figure 1: Direct-pull brake |
With the direct-pull system (Figure 1), the lever is connected to the brake by a cable. By squeezing the lever, pressure is applied to the wheel rim by brake pads. This slows the rotation of the wheel, which slows the bicycle.
This system consists of several parts:
· Rim
· Brake lever
· Brake cable and housing, with pipe
· Brake caliper
With direct-pull brakes, never use rims designed specifically for disc brakes. Rim brakes require a flat sidewall on the rim for proper braking action.
Some direct-pull brakes have a modulator, or "Power modulator." This device comprises a small spring in the pipe (Figure 1) that changes the way the brake works during the initial contact between the brake pads and the rim. As you squeeze the brake lever, you must move the lever to compress the spring before you can apply full braking power to the rim. This changes the way the brake feels, and also makes the adjustment somewhat more sensitive: if your brakes do not pass inspection, take your bicycle to your Trek dealer. for adjustment.
The brake can easily be opened if needed.
Because they are part of the braking system, also read about brake levers.
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Figure 1: Direct-pull brake |
Before every ride squeeze the brake lever firmly. It should not be possible to pull the lever fully to the handlebar. When the brakes are not applied, the brake pads should be 1-2mm from the rim. Brake pads should be aligned with the rim surface (Figure 2). If your brakes are too tight, too loose, or not centered on the rim, adjust them before riding the bicycle.
Figure 2 shows toe-in, an angular alignment of the brake pad, which can be adjusted to prevent squealing of the brakes. Used brake pads, or some new direct-pull type brakes, may not require toe-in.
Every month check the brake cables on your bicycle for kinks, rust, broken strands, and frayed ends, and check the housing for bent ends, cuts, stretched coils, and wear. Replace any part which does not pass inspection.
Every month inspect the brake pads on your bicycle for wear. Brake pads have shallow grooves in their braking surface. If any of these grooves are less than 1 mm deep, replace the pads.
Every 3 months tighten the bolts to the torque specifications.
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Figure 2: Brake pad alignment |
Turn the in-line barrel adjuster on the brake housing.
1. Rotate the centering screw (Figure 1). Turn in small increments and check for centering.
2. If the brake has two centering screws, adjust the overall spring tension while centering the brake.
1. Loosen the pad fixing bolt.
2. Align and tighten the brake pads as shown in Inspection.
3. After the brakes are adjusted, test the brakes.
Apply maximum braking force to the levers. Ensure the cable does not slip, the pads close toward the rim at right angles, and the pads do not contact the tire.
Every 3 months lubricate your brake arm fixing pivots with a light chain oil or a similar light oil.
Whenever a cable is replaced, lubricate the cable with a thin layer of synthetic bicycle grease or a similar lubricant.
