Post by warlock^_^ on Jul 23, 2004 12:38:01 GMT 8
No doubt you've seen wavy disc rotors before, but it's Spain's Galfer that has the patent on the design. The distinctive shape has two purposes: It scrapes the entire surface of the brake pad, which not only cleans the pad but also promotes even wear, and (Galfer claims) allows the brakes to run cooler.
The story most often told is that the wavy shape "pumps" air through the caliper. Galfer says that may happen to some extent, but it wasn't how the shape was designed to work. Instead, the rotor is never in full contact with the leading edge of the brake pad. The rotor moves up and down across the surface of the pad, giving one part of the pad a small break, while the other part of the pad is in contact with the rotor. As the rotor turns, the braking surface moves, giving the area of the pad that was in contact with the rotor a slight moment to cool, while the previously free area is in contact with the rotor. By keeping brake temperatures lower, it reduces fade and fluid expansion.
The thing about cross-country mountain bikes is that they're lightweight machines that operate in terrain where traction is less than ideal. Making a set of quality discs hot enough to get serious performance losses due to fade and fluid expansion is difficult, and generally rare. Whatever cooling advantage the Galfers bring to the table wasn't apparent on our project bike. They are high quality, and cost no more than most OE replacement rotors, so why not go for it when it's time to get new rotors and reap the benefit on those occasional brake-crushing downhills. Just don't expect a huge difference in most situations. The benefits of the Galfer's cooling action should be much more beneficial as the weights of the bike and rider go up, as does the length and steepness of the decent. On a DH bike, where fade and expansion is a real issue, the results could be much different than they were on our XC bike
The story most often told is that the wavy shape "pumps" air through the caliper. Galfer says that may happen to some extent, but it wasn't how the shape was designed to work. Instead, the rotor is never in full contact with the leading edge of the brake pad. The rotor moves up and down across the surface of the pad, giving one part of the pad a small break, while the other part of the pad is in contact with the rotor. As the rotor turns, the braking surface moves, giving the area of the pad that was in contact with the rotor a slight moment to cool, while the previously free area is in contact with the rotor. By keeping brake temperatures lower, it reduces fade and fluid expansion.
The thing about cross-country mountain bikes is that they're lightweight machines that operate in terrain where traction is less than ideal. Making a set of quality discs hot enough to get serious performance losses due to fade and fluid expansion is difficult, and generally rare. Whatever cooling advantage the Galfers bring to the table wasn't apparent on our project bike. They are high quality, and cost no more than most OE replacement rotors, so why not go for it when it's time to get new rotors and reap the benefit on those occasional brake-crushing downhills. Just don't expect a huge difference in most situations. The benefits of the Galfer's cooling action should be much more beneficial as the weights of the bike and rider go up, as does the length and steepness of the decent. On a DH bike, where fade and expansion is a real issue, the results could be much different than they were on our XC bike
;D ;D ;D
