Correctly tensioned brake cables are very important to the proper operation of your bike.
If the cables are too loose, you won't actually be able to pull enough on the brake levers for the braking mechanism to drag hard enough on the rim of the wheel, and thus you will have trouble stopping.
On the contrary, if the cables are too tight, your brakes will be constantly rubbing against the rim of the wheel, adding friction and making any part of the ride that much harder.
Either way, this guide will show you how to adjust the tension on your brake cable to your liking, so that you can brake when you need to and ride easily the rest of the time.
Use the two wrenches to loosen the nut that holds the brake cable to the braking mechanism.
You might want to enlist a friend to hold on to the end of the cable for you so it doesn't fall off when you loosen the nut that holds it down.
Now that the nut is loosened, pull the cable tighter or looser to adjust the resting state of the brake clamp.
Adjust the tension so that the brake pads are about 1 to 2 mm from the rim of the wheel.
When you are done, firmly tighten the nut that you loosened in the previous step.
Afterwards, you can fine-tune the adjustment by tightening or loosening the barrel adjuster located about 7 inches above the brake levers.