Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I recently changed my brake pads with some new ones that have been in my shed for years. They are not packaged, but as I am in the UK, which has a very variable climate. The shed gets very hot and humid in the day, and cools down at night.

Does this have an effect on the brake pads, with V brakes?

share|improve this question

3 Answers 3

up vote 2 down vote accepted

Almost any rubber product will degrade over time, loosing its properties. Different rubber compounds will degrade differently, depending on the formula and method of fabrication and, of course, environmental factors. This applies to brake pads, tires, grips, valve seals, inner tubes and more.

Usually brake pads tend to "dry" over time, turning less flexible and prone to cracks. A less flexible pad is less capable of creating friction. I know of some rubber (or rubber-like) products that when degraded turn to a thick paste that will stain fabrics, skin, etc. but never seen a brake pad degrade this way, if that where the case, it would not last eve one braking.

To test a V-Brake pad press hard with your fingernail on its working surface. You should be able to sink the fingernail just a little bit, leaving a pressure mark that will shortly disappear. If it feels hard, wood-like, almost sure you are better discarding it.

However, pad age is not the only factor that can degrade braking performance. Dirt and grease on pad or rim for example. I recommend washing them with liquid dish washing soap. Another factor is calibration. Brake pads not properly aligned may will not perform as designed.

Finally, there are different rubber formulas for aluminum or steel rims, (And for carbon fiber I guess) and I have tested pads that work wonders on steel are worthless on aluminum. Also have observed that the same pad can perform differently on aluminum rims made of different alloys.

<< End of answer and begin of anecdote >>

Recently I committed the mistake of trying to slowly descend a long pronounciated slope with a road bike from 1984 that still had the original pads (The ones it was originally sold with). The result was the friction generated was so poor that they only caused the rims to heat up to the point that both inner tubes were blown out. One rim was steel and the other a single wall aluminum.

share|improve this answer
    
Thanks for the answer. I might go out and get some replacement ones a bit later –  George H Apr 25 at 21:42
2  
I dispute your anecdote: the effectiveness of the brakes cannot affect whether overheating occurs, only how you use them. Any brake, if it works at all, converts kinetic energy (slowing you down) into heat. It cannot produce heat without also slowing you because that would be energy from nowhere. –  Kevin Reid Apr 26 at 4:24
1  
@KevinReid On descents, you typically do "burst braking", giving the braking surface time to cool off in between. If the friction is low an the perceived braking is not sufficient, you tend to hold the brake down, taking away the opportunity for the brake surface to cool off. –  arne Apr 28 at 9:39
    
While I'm inclined to agree with @KevinReid, there's another effect - cracks will reduce the thermal conductivity of the pad, potentially increasing the temperature of the hot skin next to the rim. –  Chris H Apr 28 at 11:01
    
@KevinReid: Indeed it was not the dryness of the pads alone what caused my problem. I am very familiar with the road I was descending, which I always do with pulsed braking (usually on v-brakes, AL rims MTB) but indeed these pads would not brake enough, forcing me to apply greater and continuous pressure on the levers. –  Jahaziel Apr 28 at 19:08

Since V-brakes use pads that are almost exclusively made of rubber or a rubber-like compound, they will have experienced some changes due to the temperature and moisture fluctuations. The rubber is most likely dried out and/or cracked and significantly harder. What does this mean for your braking ability? It means the pads won't have much grip and will instead slide against the rim. Plus, if any cracks begin to separate while riding, parts of the pad may shear off and your braking ability will quickly degrade. Since v-brake pads are relatively cheap you should invest in a new set and avoid any trouble.

Also, if the pads had been in a sealed package, they would still degrade, just much slower.

share|improve this answer

Aaron is correct. Rubber by nature will age in any environment. Even buying new is no guarantee you will get full life from rubber products. If at all possible, check manufacturing dates before purchase. Four years (shelf/use) is about the limit for effective performance. I do tend to keep the old ones laying about for a few years after replacements have been mounted, but have not yet been guilty of putting old ones back on an active bicycle.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.