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 centre of your wheel. The barrel adjuster is the metal cuff on the brake cable at your brake lever.
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.
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.
Once you've tightened or loosened the barrel adjuster accordingly, give the brake lever another squeeze to see if it's fixed the issue.
Top tip: Tightening or loosening the barrel adjuster is a quick and easy way to address braking issues if you're out on a ride. Even if it doesn't solve the problem, it might improve the situation long enough for you to get home safely and fix it properly.
Loosen the bolt on the brake caliper to readjust
If the brake lever is still too tight or loose after correcting the barrel adjuster, the cable may be too tight or loose on the brake caliper.
Take your Allen key and loosen the cable from the caliper by turning it anticlockwise, taking care not to entirely unbolt it as you'll find yourself having to reassemble the brake.
Pull or release the brake cable through the caliper
Once the caliper bolt is loose enough, it should spring back away from the wheel and cable. From here, you should pull the cable outward to tighten the brake, or allow the cable to retract inwards to loosen it.
The cable threads through a lever on the caliper that moves when you apply the brakes. When you tighten the cable, make sure the lever still has enough room to move and can't reach back so far as to hit the caliper. If it does, your braking will be obstructed and the pads won't reach the rotor. Skip to 1:11 in the below video for a demonstration of this.
Tighten the caliper bolt back up
When you've found the spot your brake pads sit comfortably over the rim and the cable is tight, screw the caliper bolt back up and give your brakes a squeeze. If they're still not quite right, it's worth revisiting the barrel adjuster to make final tweaks to loosen or tighten the brakes.
Stay safe while cycling
Knowing how to adjust your bike brakes will help you safeguard your bike in the long run. Please always make sure your brakes are working properly before riding, and always wear a helmet.