Poor stopping power does not always mean that you need new brake blocks. One simple and effective adjustment you can do without any tools is to keep your brake blocks nice and close to the sides of your wheels. Most brakes incorporate cable adjusters which let you do this. Here are some tips on using them.
If you notice that your brakes do not stop you as well as they used to, the cause might be excessive space between the brake blocks and the wheel. It’s normal for these gaps to increase as the rubber brake blocks wear away. Over time, you will have to pull the brake levers harder and further to achieve good stopping power.
Most brakes have some sort of adjusters which allow you to get your brake blocks closer to the wheel again, so you get more braking power. Each brake typically has one or two of these adjusters – the more adjusters you have, the more slack you can easily take out of the system. This photo shows a typical ‘barrel’ adjuster on a brake. Notice the small locknut (arrowed). When the adjuster is fully screwed in (as shown here), the brake blocks are furthest away from the wheel.
Whilst you are making adjustments, squeezing the brake blocks up against the wheel takes tension off the adjuster, making it easy to turn. Some people prefer to use a third hand tool to hold the brake blocks against the rim. I find that my own fingers and thumbs are more convenient.
Adjusters ought to unscrew easily by hand. If the adjuster will not budge, carefully apply a little oil or spray lubricant (like WD-40) to its screw thread and retry. Unscrewing the adjuster a few turns usually takes sufficient slack out of the cable. Do not worry if the lockring moves with the adjuster as shown here: this is normal.
Many brake levers also have cable adjusters. They are adjusted by unscrewing in exactly the same way. If you have adjusters at the brake and at the brake lever ends of each brake, there is no reason why you cannot use both adjusters to take slack out of the system. Never unscrew an adjuster so that it completely unscrews from its housing. Always leave at least two full turns engaged.
Aim to get your brake blocks as close as you can to the wheel without them touching when the wheel turns. If your wheel has significant sideways wobble, you will not be able to adjust your brake blocks so close to the wheel. (This is one good reason to get any buckled wheels trued.)
Finally, screw down the adjuster locknut so that it is finger tight. This prevents the adjuster from accidentally moving out of position, which would let your brakes go slack again.