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carbon fiber bike lateral stiffness(8 posts)

carbon fiber bike lateral stiffnesspina
Apr 15, 2003 7:51 PM
Would like to hear comments on lateral stiffness of carbon fiber bikes, in the aft area (seat stays, chain stays). An example being the lateral stiffness of De Rosa King versus Colnago C40.
pointless question...C-40
Apr 16, 2003 4:28 AM
How could any rider assess the "lateral stiffness" of these frames, even if he rode both? Unless you have some type of test equipment that would induce equal side loads on the frames and measure deflection, there is no legitimate answer to this question.

That said, I've starting my fourth season on a C-40. It's plenty stiff for me. ButI've never found a frame that wasn't stiff enough.
pointless question...pina
Apr 16, 2003 6:23 AM
I don't think it is pointless if you weigh 190 like me and have experienced wheel rub on the aft brake when climbing. Sure open up the brake a bit, but what's exceptable. And this is a steel bike. As a working dynamicist i understand your response, but i wanted to hear what people thought who had ridden several. I certainly can tell the differences in stiffness in my bikes. I can't give you an exact number, but a relative difference in general.
more likely problem...C-40
Apr 16, 2003 6:45 AM
On a C-40 the tire is so close to the chainstays (near the BB) that it's more likely that you would rub the tire on the frame. Never had that happen.

With Campy brakes you can leave a large amount of space between the rim and brake shoe and still not bottom out the brake lever. Can't imagine ever rubbing the rim on the brake.

You should not jump to the conclusion that a rim rubbing the brake shoe is due to the lack of frame stiffness. The wheel must also have adequate lateral stiffness.
I agree re: wheel flex.........roadmeister
Apr 16, 2003 11:38 AM
I have a Litespeed Classic that came with Mavic Reflex 32hole clinchers, and I could get the brake pads VERY close
to the rims. When I upgraded to the DuraAce WH-7700 wheels
a couple of years ago, I got constant brake rub when sprinting or climbing hard due to the flexy nature of the wheels. I had to space the brake pads out pretty far to eliminate this. Mounting the Mavics again allowed me to bring the pads in closer again. Brake rub would commonly be the fault of the wheel,I would think, whereas front derailleur rub would be lack of stiffness in the frame.BTW, I've not ridden any carbon other than the C40, but it's plenty stiff for me at 5'11,170. No rubbing of any kind, quiet and smooth all around.
more likely problem...pina
Apr 16, 2003 11:54 AM
It's not the wheel, a ambrosio excellence with 32 spokes that has remained true for a least 3k miles.
Just because it stays true....the bull
Apr 16, 2003 5:26 PM
does not mean its not flexing.
Just because it stays true....pina
Apr 16, 2003 8:40 PM
sure it doesn't, but it is not a soft wheel laterally in the dynamic or static sense. But i do think that the fact that it has stayed true says something about the amount of dynamic deflection (minimal). If it wasn't minimal it wouldn't stay true.