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Carbon Fiber vs. Aluminum(8 posts)

Carbon Fiber vs. AluminumAztecs
Jul 30, 2002 6:02 AM
I have a question about carbon fiber and aluminum frames (assume same components and weight). I hear the carbon fiber is a bit more forgiving and the aluminum is more stiff. If this is the case would there be a loss of power with the carbon bike due to the law of physics (since it is more forgiving I assume some energy is lost). This is probably negligible but what are your thoughts.

Might be the case, but carbon is still very stiff...andjtferraro
Jul 30, 2002 6:11 AM
b/c it is so much more forgiving, doesn't beat you up as much on long rides(centuries). Most of the TDF teams use aluminum, but there were 5 or 6 teams this year using carbon and 1 team using titanium(Lotto-Adecco's - Litespeed). Yeah, I'm sure it is negligible for most of us. Here's a great article on metallurgy, including carbon fiber that a friend sent me:

You will notice a differencejose_Tex_mex
Jul 30, 2002 6:39 AM
I have both a carbon and an Al frameset. The carbon is not as stiff as the Al, is lighter than the Al, and has a much softer ride. The Al frames definitely beat you up more than carbon.

I definitely notice a difference, especially in the hills or sprinting. The rigidity of the bottom bracket makes climbing much more efficient. Most riders need the extra help here.

One of the problems with Al is that over time, as the tubes are flexed, Al hardens. This continues to occur until it cracks. That's why Al has a lifetime. Ti frames have a longer life and carbon is somewhere in between.

Overall, if it comes down to a decision between carbon and Al, I would go with the carbon.
...over time, as the tubes are flexed, Al hardensjromack
Jul 30, 2002 7:04 AM
Not all aluminum frames exhibit work hardening, it all depends on how much it is flexed, number of cycles, etc.

A well designed aluminum frame can last forever. The trade off is weight and ride quality.

(Cannondale frames have a lifetime warranty.)
I just did a 550 mile rideonespeed
Jul 30, 2002 7:23 AM
In Europe from Amsterdam (cobblestones galore) to Paris on my Merak. While it (my Merak) is a fairly new frame and thus does not fit the criteria for an older AL frame that has hardened and thus is more prone to "cracking"; as stated by the other poster. I did ride with a guy who was 6'8" and weighed close to 270 pounds who was riding an early 90's model Cannondale.

If there was ever a time to prove the resilience of AL and the might of their (Cannondale's) engineering, this was it. This guy was a hammerhead and kept me on my toes every day. He had done the Sea Otter Classic several times and treated his bike like a monster. I predict he will be riding that frame until he just puts it away.

If a guy that big can ride the way he did over cobblestones on an AL frame that is over 10 years old, I dont think anyone riding an AL frame should worry.

my .2 cents
I sure love my '95(got it in 7/94) Cannondale mtn bike! (nm)jtferraro
Jul 30, 2002 10:56 AM
talking about damping characteristics, not stiffness nmPaul
Jul 30, 2002 9:48 AM
One more time - it ain't the materialKerry
Jul 30, 2002 4:50 PM
How a frame rides and holds up is all about design, not about the material. If two frames are competently designed with the same goals in mind, you would find minimal differences in riding them. The CF frame would be a little better at damping vibration, though some would describe that as a dead feeling. Al is only stiff if large diameter tubes are used. Throw steel and Ti into the mix and the primary difference would be weight at a comparable design point (steel = heaviest, then tough to call between Ti, Al, and CF). What has happened is that Al has been used to design low-durability and superlight frames, so people think it is lighter than CF or Ti, but at the same design point the weights are very close. All frames flex, but very little of the flex is converted to heat (the only way you lose energy). A stiffer frame may feel more responsive, but at the same design point, there is no detectable loss due to frame flex - the frame winds up and then releases the energy when the pressure is off the pedals.