If you find you have to pull hard on the brake lever to slow down, or it squeezes right into the handlebar, it's likely your brake cable needs adjusting.
There are two main points of adjustment for your cable-based disc brakes. One is at the caliper and the other is the barrel adjuster. The caliper is the claw-looking device at the disk in the center of your wheel. The barrel adjuster is the metal cuff on the brake cable at your brake lever. In this paragraph, we are going to talk about how to adjust the barrel adjuster in order to ensure your brake with appropriated tightness, and proper brake lever position.
Brake Lever Position Check
Pull the brake lever to check the tightness of your brakes
The clearest giveaway that something is wrong with your brakes is if the brake lever is too tight or too loose.
If the lever touches the handlebars, the brake cable is too loose. If you can barely squeeze it at all, the cable is too tight. Ideally, the brake lever should squeeze 1 to 1.5 inches before becoming difficult. No worry if you do not have the measurement with you, a quick life hack is to keep your brake lever parallel to the grip when a full brake is applied, and you can hardly squeeze down to the grip even further.
Brake Lever Position Adjustment
Tighten or loosen the barrel adjuster accordingly
After diagnosing whether your brake cable is too tight or too loose, you can make minor adjustments using the barrel adjuster. Tighten or loosen the barrel adjuster by turning it clockwise or anti-clockwise. This will increase or decrease tension in the cable.
If the brake lever is too loose and close to the grip, then you need to adjust the barrel adjuster away from the brake lever housing, so as to create extra tension to the brake cable. Then to tighten the brake adjuster nut to secure the position.
If the brake lever is too tight and far from the grip, then you need to adjust the barrel adjuster towards the brake lever housing, so as to relieve the tension on the brake cable. Then to tighten the brake adjuster nut to secure the position.