V-brakes were standard issue on mountain bikes until disc brakes took over but are still a very useful braking system for hybrid town bikes. They are cheap and simple to maintain and provide a good amount of braking power. Here follows an outline of the advantages and disadvantages of this braking system.
V-brakes ousted cantilevers because they are more powerful, as well as being easier to adjust. However, there has always been a trade-off in terms of pad wear cantilever pads last much longer. V-brakes stop you faster because the way they are designed pushes them onto the rim harder than cantilevers, wearing out both the rim and brake blocks faster. So, enjoy the powerful braking but remember that as a direct consequence you are going to have to learn to inspect brake blocks frequently for wear and replace them. Depending on where and how you ride, you can wear out brake blocks at the rate of a set per day, and through a rim in a matter of months.
Keeping blocks and rims clean will make a huge difference to how long they both last. Dirty rims will wear out brake blocks, while flakes of grit and metal caught in your brake blocks will scour the rim surface. It’s easy to forget that the rims are an integral part of the braking system. Unless they’re clean and flat, the brake blocks
will struggle to grip them and stop you in your tracks.
This section takes you through the processes of checking that your V-brakes are set up and working correctly, fitting new brake blocks, fitting a new cable and servicing your brake units. Careful brake-block alignment and smooth cables will help you get the most power out of your brakes. You’ll also get more feedback from them. Good set-up means that when your hands are on the brake levers, you will be able to feel what effect the brakes are having, increasing your control over the bike. Good brakes don’t just lock the wheel up, they allow you to control your speed accurately.
One important thing to remember is that brake blocks and cables often just need cleaning rather than replacing. Cables can be cleaned rather than replaced as long as they’re not frayed or kinked. Use the following procedure for replacing your cable. Keep to the instructions for removing the old cable, then clean it with a light oil like GT85. If necessary, soak congealed dirt off with degreaser. Cut the end of the cable off cleanly so that it can be neatly threaded through the outer casing. Clean the inside of the outer casing by squirting spray oil through it to flush out dirt. Replace any sections that are cracked, squashed or kinked. Replace bent ferrules. Then refit as a new cable.
“Brake blocks and cables often just need cleaning rather than replacing”
Worn-out brake blocks
Brake blocks must be replaced if they’re worn below the wearindication lines stamped on the block. If there are no wear lines, replace the brake blocks when you’ve worn down to the base of any grooves moulded into the block. They’re also due for replacement if any of the metal over which the rubber block is moulded is showing through. Otherwise, they can be cleaned and freshened up. Follow the instructions for removing the blocks. Use a sharp knife to cut off overhanging lips at the edge of the brake block, and use clean sandpaper to flatten the braking surface of the block. Pick out any flakes of metal or grit. Refit as new brake blocks.
V-brakes are bolted onto your frame or forks by studs called brake pivots. Newer, disc-only frames and forks, as well as road bike frames, don’t have these pivots, and so cannot be fitted with V-brakes. Currently, many new hybrid bikes have both disc mounts and V-brake pivots, allowing you to upgrade from V-brakes to discs.
The brake units are designed to rotate around the pivots so the condition of the pivots is important. If the surface is rusty or corroded, your brakes won’t pull smoothly onto the rim or spring back smartly. If your brakes are sluggish and fitting a fresh cable has no effect, see page 60 to service your brake units, and to clean
and oil the pivots.
Crashing can also bend the brake pivots, preventing you from adjusting them properly. Look at the brakes from face on: the front brake from in front of the bike, the rear brake from behind it. You’ll see the heads of the two brake-fixing units at the bottom of each unit. These should point straight out from the frame so that the bolts are parallel. Bent brake units don’t just make it awkward to adjust the brake block position, they can also be a liability. Many fork pivots, and some frame pivots, can be replaced; check with the manufacturer for spares. Although, if you have disc mounts as well as V-brake pivots, this could be a good excuse for an upgrade.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES