How to Adjust
Many bikes, especially mountain bikes, use V-brakes (also called direct-pull or linear-pull brakes). In this powerful brake design, the cable enters the brake area from the side, rather than from the top as is common in other brake styles.
This brake cable attaches to each of the arms of the brake mount, which pivot on the frame of the bicycle. When the cable is pulled, the arms of the brake mount are pulled together and the brake pads are brought into contact with the rim of the tire. This design provides a good deal of stopping power and is common on mountain bikes for its usefulness during rapid trail rides.
V-brakes don't take much to get out of alignment or have other issues. Luckily, adjusting this design is easy and straightforward.
Time required: 10 minutes
#5 and #6 Allen wrenches (aka hex wrenches)
Needle-nose pliers (optional)
Step 1: First, let's make sure you actually need to adjust your brakes. With your hands on the handlebar in a normal position, pull the brake lever you wish to adjust (this technique is the same for either front or rear brakes). Most often, the problem you will have is that your brakes won’t be engaging strongly.
Step 2: If your brakes are not engaging strongly (you pull the lever strongly and the brake does not engage strongly), the first step is to adjust your barrel adjuster. This changes the tension in the brake cable, and is located where the cable exits the brake-lever mount on the handlebar. Trace this down to the brake to make sure it is the correct cable, then look for the barrel adjuster: a small grooved ring, usually black or silver. Screw the barrel adjuster outwards as far as it can go (any further, and it will release entirely from the mount). This tightens down your brakes.
Note: the barrel adjuster can be used on the road for on-the-fly adjustments of braking tension.
Step 3: Now we need to adjust the tension on the brake wire at the other end. With your allen wrench, loosen the bolt on the brake lever until the wire is free to slide side to side.
Step 4: Using one hand, pinch the brake levers together until the brake pads are firmly seated against the rims of the wheel. Now, using your other hand, re-tighten the bolt that holds the brake wire in place.
Step 5: Check for tension by attempting to spin the wheel; it should rub on the brake pads and not spin freely.
Step 6: This is the final step. Move back to the barrel adjuster and screw it back in towards the brake lever, the opposite direction that you originally did. This will release tension on the brake cable. Release the screw fully, and your cable tension should be ideal, providing strong, powerful braking action.