How to use a barrel adjuster:
Barrel adjusters are a good way to make quick adjustments to your bike without using a tool. You make adjustments by tightening or loosening the screw. If the brakes are too loose and aren’t responding well, unscrew the barrel adjuster counter clockwise, then screw down the lock ring to make sure it stays in place. This will increase the tension on the brake cable helping it to respond quicker.
If you have the opposite problem, and your brakes are too tight. Loosen the cable by screwing the barrel adjuster in. Adjust to your personal preference.