On-One Carbon 456 – how flexy is carbon fibre??

Just took delivery of one of these today- is it normal to be able to deform a carbon fibre tube by pressing on it with your thumb??

Bit disconcerting….

You’ll be sending that back, I’m afraid. Unless you have bionic thumbs…?

Yes its okay

But be careful in the winter because carbon fibre goes brittle in cold weather

I could do the same with my carbon XTC, just don’t do it.

common test carried out on carbon fishing poles, some of which cost in excess of £4k, section strength tested by squeezing, as for carbon being brittle in the cold, never seen any issues with carbon fishing rods being bent double in sub zero temps

I can do that pretty easily on some sections of my Vertex RSL.

fadda – Member
You’ll be sending that back, I’m afraid. Unless you have bionic thumbs…?

What a load of crap.

It is perfectly normal. The frame is so thin in places that yes you can deform it easily with your hand but don’t worry.

compressive strengths of CFRPs are pretty poor, and if in the transverse direction too, i’m not surprised. I’m not sure if it’s worthwhile sending back as I’ve never had a c.f. bike 🙂 If you couldn’t compress it then I’d guess it’d be very thick and overengineered.

I’m not sure if it’s worthwhile sending back

It’s not. They’re all like that (C456s that is) Well, mine and the other 2 I’ve seen are like that anyway.
FWIW the C456 is a fairly overbuilt frame these days. Chunky and strong. 🙂

Maybe I have weak thumbs, then… 🙁

you can do this on most lightweight aluminium frames too! Certainly could on my old Klein.

The TT on my road bike compresses significantly in the hand too, worries me that it will slip out of the clamp when being transported by car.

Cheers folks, reassuring. Always had steel or alloy frames before.

It’s not really anything to do with poor compressive strength of CFRP.

It is actually far simpler than that and to do with the geometry of the top tube which has quite small radius top corners with a wide curved top piece and the fibre orientations along the top tube will be predominantly along it’s length for stiffness in the main load direction and in +/- 45 deg for torsional rigidity and robustness. 90 deg fibres will most likely be there but they are not as important for the overall load case and i would rather the frame is designed to flex like that than be overly rigid and fail at a corner.