V brakes are used by most touring and commuter bicycles. To make sure that your V brakes are functioning well, you need to keep them properly aligned and adjusted. The high mechanical advantage of the brakes means you have to pull your cables tightly to get the brake shoes to move. If these are not properly adjusted, your bike's braking power will be reduced dramatically.
Inspect the brake pads of your bike for proper alignment with the rim's brake surface. Loosen the bolt of the brake pad using your hex key if they are in contact with your rim body or tire, or if they are uneven.
Hold your brake pad in place using one hand. Close the brake lever and align your brake pad with the bike rim. Hold your brake firmly closed while you tighten the bolt of the brake pad.
Open and close your brake lever, and watch your brake pads closely. Make sure that both of your brake pads remain in contact with the surface of the rim at the same time.
Use your screwdriver to loosen your adjustment screw of the brake that touches the bike rim first. This screw is right below your return spring, near your bike fork.
Tighten your other pad's adjustment screw if your first brake pad's return spring cannot be loosened any further. This should show the same effect.
Squeeze your brake lever with your pliers and watch your brake pads as closely as possible. Make sure that your brake pads touch right at the same time. Make smaller adjustments to your adjustment screws until they are able to function properly, if the brake pads do not touch at the same time.