Disc brakes slow and stop a bike by means of friction created when brake pads are pushed against a metal brake disc mounted on the bike wheel. The primary advantage of disc brakes is stopping power -- riders tackling the steepest downhill terrain use powerful hydraulic disc brake designs that enable them to stop on a dime.
Many modern mountain bikes use disc brakes, and some designs of cyclocross and road bikes employ them as well. Disc brakes are preferred by riders who deal with wet, muddy or icy conditions on a regular basis, as they can provide better stropping power in these conditions.
Like most other bike components, disc brakes benefit greatly from regular maintenance and occasional adjustment. The most common problem encountered with disc brakes is caused by the brake pads rubbing against the surface of the brake disc. Luckily, this is an easy fix with most designs. Let's jump into the nitty-gritty of the basic procedure.
Tools You'll need for the Job
Allen wrench (hex wrench) Set
Needlenose pliers (optional)
Time Required: 15 minutes
Step 1: First, let's take a look at the brake mechanism to check out the alignment. Flip your bike upside down and sight along the metal brake disc. Note how much spacing exists between the brake pads and the brake disc -- a standard gap is one to two millimeters.
Step 2: Spin the wheel and note any warping or damage to the brake disc. Note any wobbling or thinning of the brake disk. If there is severe wobbling or wear on the brake disc, you may need to replace it. Consult an expert for this operation.
Step 3: The entire brake caliper/pad mechanism should be parallel to the surface of the brake disc. If the alignment is not correct, it can be easily adjusted. Using your allen wrench, loosen the bolts attaching the brake caliper/pad mechanism onto the bike frame. This will allow you to slide the caliper/pad mechanism to one side or the other. Take this opportunity to align the caliper/pad mechanism and to correct any gross imbalances in the spacing of the pads.
Step 4: While the bolts are loose, look on the outside of the caliper/pad mechanism. You should see a wheel or knob that can be turned. This adjusts the spacing between the pad and the surface of the brake disk. Turn the knob clockwise until the outer brake pad just touches the surface of the brake disc.
Step 5: Now find the pad adjustment knob for the inner brake pad. Again, turn the knob clockwise, but this time go beyond simply touching the surface. Tighten the pad firmly against the surface of the brake disc. This pressure will align the brake pad with brake disc.
Step 6: With the pads and brake disc now securely aligned, retighten the bolts attaching the caliper/pad mechanism to the frame. Loosen the outside adjustment knob until the brake pad just clears the brake disc. If necessary, loosen the inner adjustment knob to do the same for the inside brake pad. Allow just enough space for the brake disc to spin freely when the brakes are not engaged.
Step 7: Now that the pads are aligned and spaced correctly, we can adjust the brake cable tension. First, release the tension by loosening the bolt that holds the cable in place on the caliper/pad mechanism. This will require an allen wrench.
Step 8: Using one hand, press the brake pad mechanism in an engaged position, with both pads engaged against the surface of the brake disc. Using the other hand or pliers, pull the brake cable into a tight position, then retighten the bolt to hold the cable in place.
Step 9: Test the tension on the brake cable by holding your handlebars normally and pulling the brake levers. Your brakes should engage firmly near the middle of their range. If necessary, adjust the cable to increase or decrease tension. Fine tune the feel until braking is smooth, strong, and consistent. Now get out there and enjoy the ride!