Reins said:IAre aluminum bikes more responsive then CF bikes in that they have harsher ride? Like with cars a rigid car handles better then a luxury car because they are more rigid and minimize body roll. Am I correct with this or just insane?
You are not insane, but only partially correct. Flex can diminish accelleration, and stiffness can cause a harsher ride, but a bike does not have to be harsh to be responsive.
One major difference between aluminum and carbon fiber is that aluminum is stiff equally in all directions. Carbon fiber is stiff only in one direction. By orienting the strands of the carbon in specific directions, it is possible to make a frame that is stiff and responsive where it counts (e.g., the bottom bracket and chain stays) so that all of the energy going into the crank is used to turn the wheel instead of being wasted on lateral movement of the frame, but still flexible in areas that improve comfort but have little bearing on efficiency (e.g., the fork and seat stays).
There is also a difference in preception that might not be real. A harsher bike might seem faster, but it is difficult to prove that it actually is faster. If, for example, a harsh bike causes the wheel to bounce, the time that the wheel is in contact with the road surface is decreased; thus, while the transfer of energy from the crank to the wheel might have improved, the transfer of that energy from the wheel to the road is diminished. On a softer bike, there might be some loss of energy between the crank and wheel, but no loss of energy between the wheel and road. The harsher bike will seem faster, but the softer bike might actually be faster. The reality, though, is that there likely will not be any difference in speed between the two bikes.
Esse Quam Videri (to be rather than to seem - state motto of North Carolina
What does make a difference in responsiveness, though, is the rotational mass of the wheel. It is extremely easy to show that my carbon fiber Specialized Roubaix Elite is much more responsive than my aluminum Specialized Crossroads Elite. The heavy frame of the Crossroads is much stiffer than the light carbon fiber frame of the Roubaix, but the wheels on the Roubaix weigh less than one-third of what the wheels on the Crossroads do. Even though there might be some loss of energy between the crank and wheel on the Roubaix, it takes so much less energy to get those wheels spinning compared to the Crossroads that the Roubaix is far more responsive.
All of the above notwithstanding, when it comes to road racing, and especially triathlons, the two biggest robbers of speed and energy are wind resistance and fatigue. An excessively harsh ride will contribute greatly to the fatigue factor and far more than offset any potential gains in responsiveness. Responsiveness is only important in accelleration. Most of a triathlon ride or a road race is endurance. If aluminum (or steel or titanium) was better overall, then the pro tour riders would be using aluminum (or steel or titanium). The fact is, though, that very few pro tour riders use anything other than carbon fiber.
