01 August 2003
01 August 2003
Lance Armstrong gained a fifth consecutive win in the Tour de France, but beneath the battle of the cyclists is the battle of bike-frame technology.
Armstrong rode a carbon-fiber bike designed and built by Waterloo-based Trek Bicycle Corp. Weight is the driving force behind bike design, which led to high-end carbon fiber and new aluminum alloys."They're all very similar frame weights," said Glenn Daehn, professor of materials science and engineering at Ohio State University, but each has its own unique response.
"In a bike frame you need something that's pretty stiff," said Bruce Pletka, professor of materials science and engineering at Michigan Technological University in Houghton. But what really matters is toughness, strength and how many times a material can withstand small stresses before failing, he said.
Aluminum has a reputation for being stiff, which can be hard on the rider over long distances because it doesn't absorb shock very well, Daehn said. But too much springiness in a frame makes the bike less efficient for the rider.
A carbon-fiber frame is stiffer than aluminum but can better absorb the vibrations of the road, said Steve Swenson, a technician at Trek. "It transmits vibration less harshly than aluminum," which translates into a more comfortable ride.
More riders are choosing to enter the Tour de France with carbon-fiber bikes than ever before, said Jim Colegrove, a manufacturing engineer of composites at Trek. Aluminum, though, still remains a popular favorite.
For non-professional riders, evaluating a bike frame involves many factors. Some are technical, and some purely subjective, such as ride quality and feel. And some are purely financial. A carbon-fiber bike can cost almost 11/2 times as much as an aluminum bike with the same components, Swenson said.