No matter what kind of bike you have, the tension on your brakes is controlled by one of two things: a brake cable or hydraulic fluid. If you have hydraulic disc brakes, there’s not a lot that you can do to adjust them, other than bleeding them, which is generally a job best left for professional mechanics. However, if you have rim brakes or cable-actuated disc brakes, adjusting your brakes is pretty simple and should be something you can do at home.
Make Small Adjustments With Your Barrel Adjusters
If you have a mountain bike, hybrid, or city bike, you’ll notice that there are screw-like adjusters on your levers where the brake cable housing meets the lever. If you have a road bike, you’ll notice a similar adjuster on the brake itself, again, where the cable housing meets the brake. These are called barrel adjusters, and they allow you to take up cable tension, which brings the brake arms closer to the rim of the bike (or the pads closer to the rotor in the case of disc brakes).
If your brakes are too loose, and you have to squeeze the levers all the way to the handlebar to get any kind of stopping power, you’ll want to loosen your barrel adjusters a few turns. This actually tightens the brake cables and therefore tightens the brakes. If your brakes are so tight that they don’t let your wheels turn, then you can tighten the barrel adjusters back down and make some room.
When You Need to Make Bigger Adjustments
These small adjustments don’t require any tools, and you can even do them while you’re riding your bike if you have good enough bike handling skills (but it’s much better to do it while the bike is not in motion). If you’ve already turned a barrel adjuster all the way out or all the way back in, though, you’re going to need to grab either a five-millimeter hex wrench or a ten-millimeter box-end wrench (depending on your brakes).
With your wrench, loosen the pinch bolt that holds the brake cable in place. Then roll your barrel adjuster about halfway out. Pull the cable tight and put enough tension on the brake that it lightly touches the rim. While you do this, tighten the pinch bolt down again. Then roll the barrel adjuster back in, and you should have a well-adjusted brake. If not, you can play with how far you roll the barrel adjuster out and/or how much tension you put on the cable as you tighten the pinch bolt back down. With a little bit of patience, you should be able to adjust your brakes without much trouble at all.
Good luck, and, as always, if you run into too much trouble, don’t hesitate to take your bike to your local bicycle shop for some professional care.