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I've been reading a bit about riding and braking techniques (http://sheldonbrown.com/brakturn.html) and I'm having some trouble pulling off the hard front brake.

I believe this is the style of brake that I have on my bicycle: enter image description here

However, when I apply my front brake, with maximum force - it doesn't seem to be nearly enough to send me over the handlebars or skid the tire. I slow down, but it seems to be fairly gradual.

I've adjusted my brakes myself (possibly, I've done it incorrectly...) but there is very little clearance between my rims. My wheels both seem to have a very tiny wobble that prevents me from setting my brakes any tighter, but when I pull the brake it feels fairly soft, almost as if the cables have some stretch to them?

My real question here is what can I do to improve my braking time? Does it sound like I've done something wrong. I did have the brake pads replaced once before, but they appear to be in good condition.

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If you have a wobble in the wheel it's out of true. True it (or take it to your LBS to have it trued), then you can adjust the brakes properly. –  Ken Hiatt Jul 8 '13 at 5:44
    
V brakes can range from cheap and nasty chain store systems to 15 years ago being the only option even on the very best down hill bikes. I have a retro bike I still ride occasionally and its brakes would out perform most low end discs..... We really need to know what you have to answer better. –  mattnz Jul 8 '13 at 9:16
    
the cable might slip from the clamp ensure that it is tight enough, also check the brake lines if they are springy (you can bounce the handle a bit when on full tension) then you might wanna consider a replacement –  ratchet freak Jul 8 '13 at 20:32
    
Do you have a co-op near you? Have you ever dropped by? –  unforgettableid Jul 14 '13 at 16:17

4 Answers 4

First off, if anyone has mucked with the components on the bike it's possible that they exchanged either the brake levers or the brakes themselves and produced a mismatch where the levers are not capable of providing enough pressure. But this shouldn't be a problem if the bike has all it's original components.

And if, when you squeeze the brake levers, they "bottom out" against the bar, that indicates that they're misadjusted or the cables are rusted/worn. (If, due to wheel wobble, you can't adjust tight enough to prevent bottoming out then you need to get the wheel trued.)

But failing those, likely it's a problem with the brake pads. First make sure they are squarely pressing against the side of the rim and have not gotten twisted to where they're making poor contact. And check to see that the pads are not worn down to where the metal pad holder is close to hitting the rim. (Note that the rear edge of the brake pad will tend to wear faster than the front -- simply because the pad looks good from the front does not mean it is good.)

If the pads are not worn out (and they don't have oil on them or some other such problem) then it's probably just a problem with pads that are too hard and you need new pads that are a little "grabbier". This is, to a degree, a personal choice thing, as there are different pad materials with different characteristics (and most people don't like pads that grab too much), but it's also true that a given set of pads will get harder and brake more poorly as they get older and more worn.

One last possibility is that you have the rare case of steel rims (usually only seen on very cheap bikes). Brakes don't work nearly as well on steel rims as on aluminum, and so for steel you need pads that are quite "grabby".

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Let's asume your levers are a correct match for the type of brake you have. Also, let's assume that you have a "normal" strength in your hand (say, you can actually lock the wheel in another bike) There are a list of factors that decrease the braking power of a system, some are easier to overcome, I'll try to list them from the easiest to the most difficult/expensive.

Braking surfaces are contaminated

Oil is the most common, specially on rim brakes but can happen to disc brakes too. Dirt and debris can get stuck in rim brake pads an even in some rims. For rim brakes my preferred cleaning method is washing the rim and pads with liquid dishwashing soap, aided with a half worn dish washing pad (the normal ones are usually green, but there are white ones that are softer an designed for anti adherent coated cookware, these can be used new). Be sure to wash the contact surface of the pads.

If the pads have cristalized surface due to excessive heat, they are "too hard" on the surface, so they do not provide enough friction. Cristalized rim brake pads have black and shiny bands in the contact surface. That can be cleaned using medium grit sandpaper (240 to 600). Buff the surface just enough to reveal the still porous rubber underneath.

If there are small dirt particles, metal shreds our other foreign material embedded in the pads, they reduce friction and scratch rim's surface, remove them using a sharp tool, like a thin screwdriver, a spike or a large seewing needle.

Aluminium rims can be cleaned with the same soap and washing pads. If necesary, a slight resurfacing can be done with near 800 grit sandpaper. This is specially useful if rubber has stuck to rim surface (you'd see small black stripes of rubber in the braking surface of the rim). Steel rims, specially the crome plated should be cleaned with the same soap, but use a towel instead of a scrubbing pad. Do not use sandpaper on cromed rims, you'll damage the finish and the rim will start to corrode earlier.

Disc Brakes are less prone to contamination but are still vulnerable. Oil can get in the rotors and be draged to the pads. The rotors can be cleaned with dishwashing liquid ad a towel, or rubbing alcohol and a clean rag. Disc brake pads that become contaminated with oil can be very difficult to clean. Some types can be cleaned with rubbing alcohol, but if the problemm is too aggravated it may be better to change them.

Disc brake pad cristalization is more difficult to identify but the main symptom is a shiny surface (normally the surface is dull) medium fine sandpaper can be used to solve the problem, grit 1000 or approximate. Note that the material of some disc brake pads have metal particles as part of their composition, so small shiny grains are normal in those cases.

Incorrect adjustment

There are so many different types of brakes, and so many different designs among them that I cannot give extensive advice, so my recommendation is to refer to the user's manual if available. Common types of brakes like v-brakes are well known and there is plenty of tutorials available. Most of them (including the ones shown in the OP pictures) can be adjusted using the same instructions, so, almost any adjustment or installatin manual would do.

As for lever reach, travel and position how ever, a badly adjusted lever may give you a hard time. Reach is how far you have to strech your fingers to actually start to pull the lever. Travel is how much you need to move the lever before the brakes engage. Position is wether the lever is actually within the reach zone of your hand. Particularly, travel and position can reduce your ability to actuate the lever, thus your braking power.

Lever travel should be such that the brakes engage when your hand is in the strongest part of the grip. If the travel is too short your fingers are too stretched to pull effectively, if its too long your fingers are too curled or the lever bottoms out against the handlebar. The lever should also be in an angle that doesn't force you to bend your wrist in order to actuate or reach it, the hand should remain in a fairly natural position.

Most levers have small bolt near the handle pivot for reach adjustment. Travel can be adjusted by changing cable tension. Position and angle is adjusted by loosening the fixing bolt, reposition the lever and tighten the fixing bolt.

Old or wrong pads

Aged pads loose flexibility and turn into hard bricks that do not povide friction. Also, there are pads made of a too hard compound with the same consequences. Most brake pads are not expensive, so replacing them should not be too difficult. Finding the best pads is the difficult task, as there are too many options available. You may need to try several options before finding your personal favourite, but once you do, it pays back highly. Do not trust internet reviews to much, as you don't actually know the reviwer or the use he/she tried to do with the items. If possible, ask a fellow rider who uses a similar setup and does a similar type of riding, borrow te bike for a little brake test and observe what pads are installed. Note the make and model of the pads.

Cables in bad condition

When a cable is bent, rusted or dirt inside the casing it causes additional friction. You have to overcome this friction to actuate the brake, so it also lessens your braking power. Cables should be inspected disconnecting them and testing if they slide easily in and out. Any fraying, rusting, casing crushed, bent, worn, is also a bad sign. The most straightforward solution is to replace them.

Stuck pivots

Vbrakes, cantilever brakes, and caliper rim brakes can suffer from being stuck due to rust or dirt and clogged oil or grease. To test, disconect the cable and actuate them directly by hand. They should move smoothly and easily, opposed only slightly by the return spring. Shall this test fail, disassembly, cleaning, lubricating and re-assembly should fix the problem.

Some mechanical disc brakes can suffer from this too. Hydraulic brakes don't.

Bad design / wrong application

Some brake systems are simply not good enough. They don't have the right proportions to give the required mechanical advantage or are made with bad quality materials that flex too esily. On the other hand they may just be fitted to a bike they were not designed for. If you got the bike fully assembld from a reputble dealer, and it is from a reputable maker, this is the less likely case, but if all the tests and possible adjusntments have been made, and yet you cant't get the braking power needed, the only solution may be to change the model, brand or type of brake system.

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Take a look at your rims to see if you have any contaminates on the brake surface. Wipe the rim with some rubbing alcohol and see if there is any improvement. Brake pads are made of different material with different properties. Some are very hard and have long life, others are softer and stop better but at the expense of durability.

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When you're adjusting the position of the brake pads, you must squeeze the brake and check the closed position. The pads should line up nicely with the rim in the braking position. With the pads loosened, squeeze the brake with one hand, and adjust their position with the other hand, without losing a grip on the brake, and tighten them to fix the positions. Then release the brake and tighten the pads more, to fully secure them, ensuring that they do not rotate or move during tightening. Squeeze the brake again and check the position and fix if necessary.

Make sure that you understand the brake wear compensation bolt, located at the grip. As the brake pads wear, this hollow bolt is unscrewed to compensate (tighten the cable). It has a nut on it which is then used to tighten it in a given position. Manipulating this bolt and nut is a key skill for the cyclist with these types of brakes.

This wear compensation bolt can be a useful tool in setting up the brakes:

  • Loosen the bolt almost all the way out (loosening it tightens the Bowden cable).
  • Next, loosen the cable retaining bolt at the brake, and squeeze the brake all the way to the rim. Now clamp the cable securely in this position.
  • The brake now cannot be used because it is tightly closed. However, the wear compensation bolt on the brake handle is unscrewed almost the way out. What you do now is screw that bolt all the way in, which opens up the brake.

Another way is to use some kind of shim between one of the pads and the rim when squeezing the brake. Clamp the cable and remove the shim.

*V-brakes are strong when you have correctly positioned pads in good condition, with about 1/8" clearance from the rim of a wheel that is clean and true, everything is tight, and the cable and brake lever hardware are in good condition. *

If your wheel has significant runout, you can still have decent braking power, because the V-brake arms will move from side to side to track the runout. However, the brake pads may rub on the wheel when you are not using the brake, which robs you of energy and wears the pads. Learn how to true a wheel, or have it done. (If you have it done, you might as well have the shop tune up your brakes for a package deal tune up price.)

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