Linear Pull Brake Service (V-brake style)
Useful Tools and Supplies
- Repair Stand, holds bike secure for easy work.
- Hex wrenches (commonly 5mm and 6mm)
- Cable cutter, Park Tool CN-10
- Grease, Park Tool Polylube® 1000
- Light liquid lubricant
- File, or grinder to finish housing ends
Properly adjusted brake systems require attention to small details. This article will begin by discussing the brake lever, inner wire fitting at the lever, and brake housing. Caliper attachment to the frame, pad adjustment to the rim, and pad centering and clearance are then reviewed.
Brake levers should be positioned so they are easy and comfortable to reach. Loosen the lever mounting bolt and rotated the lever so it is in line with the rider's arm, making it comfortable to reach and use. Re-secure brake lever body. Additionally, brake levers commonly have a setscrew on the lever body that allows the lever to be set closer to the grip. Use reach-setting screw to adjust lever reach according to hand size and riding style.
The cable system connects the brake lever to the caliper at the wheel. The brake inner-wire has a fitting on one end, which sits in the lever. Upright bar levers use a round disc shaped end about 7mm (9/32") in diameter.
The brake inner wire end is held by the lever. The common system is shown below. Align the slot in the barrel and adjust with the slot in the lever body. Fit the disc into the lever and pivot the wire into the adjustingbarrel. Turn the barrel to hold the inner wire in place.
The Shimano® levers may use a clamp on the lever. Pull this clamp upward, and fit the inner wire disc in place.
The inner-wire passes through a brake housing, which allows the inner-wire to connect from the levers to housing stops on the frame. Housing also allows for bends around corners on the way to the brake caliper.
To determine correct housing length, see Housing Length.
Calipers and Pads
Linear pull calipers are attached to the frame or fork at the "braze-on". If you are mounting the calipers or have removed them, grease the braze-on before installing the caliper. There may be three different spring hole options, it is typically best to choose the middle hole.
Brake pads are bolted to the caliper arms. When the bolt or nut is loosened, they can be adjustable in several directions. The pad should be correctly adjusted for vertical height alignment, tangent alignment, vertical face alignment and pad toe. Not every brand or model of brake caliper has every adjustment, and sometimes you must simply compromise when setting pads.
Vertical height alignment: This is the setting up and down on the rim-braking surface. View caliper face-on and move the arms, watching the pads move to the rim. For most linear pull calipers, set the pad to the upper edge of the rim-braking surface.
Some linear pull models, such as Shimano® XT and XTR, use a parallelogram movement for the pad, and the pad travels straight to the rim. Set these pads to strike in the middle of the rim-braking surface.
This is the setting of the pad tilt. Viewed from the side, the front and back of the pad should be level to the rim. One side should not be higher or lower than the other side. Use care when tightening the pad fixing bolt and hold the brake pad to keep it from twisting.
Vertical face alignment
This is the setting of the pad vertical surface relative to the rim vertical surface. The vertical face of the pad should be set parallel to the face of the braking surface.
This is the setting of pad angle as it touches the rim. Toeing refers to setting the pad so the pad's front edge strikes first, which tends to reduce squeal during braking. Caliper arms tend to have play in the pivots and the arms flex when the brake is applied. This may cause squealing in the brake pads. It is simplest to first ride the bike and see if the brakes squeal.
Front of pad strikes rim first for "toe".
Most models of linear pull calipers use a "threaded stud brake pad." Some models use a smooth stud pad with fixing bolt. For the threaded stud types, a threaded bolt is fixed into the pad. The bolt is sandwiched to the caliper arm by a series of convex and concave washers, creating a ball and socket system. The bolt and pad move in the caliper arm for toe and vertical face alignment.
Threaded-stud pads use curved washers to align pad face to rim.
Before setting pads, begin by double checking that the wheel is adequately centered in the frame. If the wheel is moved from current position, pad alignment will be effected.
- Loosen pad nut/bolt and lubricate curved washers and thread. Adjust one pad to the rim at a time.
If desired, install rubber band shim at back edge of pad. This helps to set the toe.
Push the caliper arm to the rim and view pad alignment. Align pad correctly in four positions.
- Set the pad's vertical height on rim braking surface.
- Set the pad's vertical face to be parallel to the rim's face
- Set front and back edge of the pad to be level to the rim, so it is tangent to the rim.
- If toeing with a shim, set it so the front edge and back edge with rubber band should be touching the rim at same time.
- Tighten pad nut and remove rubber band. Inspect pad alignment again.
- Repeat alignment of other pad.
Attach the inner-wire to the brake caliper. Secure the wire fixing bolt. Squeeze the lever hard several times and set pad clearance at the lever for rider preference. If the brake feels tight, turn the barrel adjuster into the lever clockwise to loosen inner-wire tension. If the brake feels too loose, turn the barrel adjuster counter-clockwise to tighten inner-wire tension. If barrel adjuster is all the way engaged at lever and the brake lever is still too tight, loosen the inner-wire pinch bolt and allow the slack to feed through pinch plate. Tighten the pinch bolt and test again, doing final adjusting at brake lever barrel adjuster.
Use barrel adjuster to set tightness of pads to rim.
Inspect the pad centering to rim. Use a set screw on sides of caliper to center pads to rim. Tighten the set screw on the arm with pad that is closest to rim. Inspect that pads are not rubbing tire. Re-adjust if necessary. Clean the rim surface and test ride bike.
Use centering screws to move arms and center pads to rim.
Pads will wear out with use and require replacement. Pads will also harden and become ineffective with age. Pads may also become embedded with aluminum or other contaminants. Inspect and remove as necessary. Pads that are aligned too low on a rim will tend to develop a lip on the low edge. This lip makes correct alignment impossible.