Originally Posted by
Italuminium
My guess is that these grab-release cycles occur in all brakes, but due to arm lengths, pad composition and braking force fall usually out of the audible spectrum, either by having too high a pitch or the sound being so soft that it's not audible over environment noises unless you get really close. I think the movements of the calipers are well within the material tolerances and fatigue limit of the brakes, so no worries there. Also, the release cycles are a good thing - locking up your wheels all the time would be very dangerous. Plus, repeated cycles only increase friction and that's what you want, because braking in the end is the transformation of kinetic energy in heat, sound etc.
My verdict: not a bad thing. But an annoying thing.
These grab-release cycles are a fact of life. Any braking surface is going to do it -even on cars/motorcycles. Brake surfaces can't "slide" by each other but will necessarily cycle at a frequency determined by the co-efficient of friction of the braking surfaces, the amount of force squeezing them together as well as the resonant frequencies of the parts involved. The trick is to avoid having the frequency of this oscillation within the human range of hearing purely for aesthetic reasons.
Many times the effort to keep the vibration out of the human hearing range causes the designers to choose materials or designs that are less-effective at the primary job intended (braking) in order to meet the aesthetic audible (or inaudible as the case may be) demands of the brake.
Big truck brakes, or those used in high-performance racing applications often tend to make more spurious noise as the requirements for fully-effective brakes simplhy outweigh any cosmetic or aesthetic considerations.
But on a bicycle, where braking performance is typically abysmal anyhow, and the requirements are not that great in the first place, it's fairly easy to tune out audible brake noise without giving up anything in actual braking performance. Usually just fiddling with pivot fastener tension/slack and toe-in it can be easily tuned out of the audible range.
-My $.02