I have thought about the carbon steerer strength issue on a TT bike before. But if you think that road bars go up to 46cm width and TT bars rarely go above 40cm then surly this gives less leaverage to apply force through the stem to the steerer. This coupled with the fact that you don't sprint on a TT bike would surly mean that a carbon steerer on a TT bike would see less force acting on it than on a road bike
What do you guys think
I agree, the road bars will have more force on them than the TT bars. You should'nt rock the top half of your body when time trialing anyway, its a waste of energy.
I don't think that's the issue that other people are wondering about. It's not lateral, it's front to back (if that's how to put it... i don't know)
You're out front on the aerobars, applying your weight on the ends of the bars (although most of it goes onto your elbows, I'd imagine).
However, there's more torque that can potentially be applied - I just looked at my aerobars (clipons) and I'd guess they're about 30cm long. if you look at the formula for torque, it's Force x Distance. On a handlebar you're looking at a clockwise torque of .21*F and a counterclockwise torque of .21*F again, where F is the force your hands are applying to the hoods or whatever. The torques cancel sort of - if I'm correct they just 'change' into a downward force - no torque on the steerer tube, no concerns.
The aerobars don't mount in the middle, so they're not .15*F, etc. Since both hands are in the same location, I'm going to use 2F (since F was the force each hand was exerting in the previous equation.).
2F*.3 ahead of the tube. There's nothing to cancel the torque, so there's forward torque (ie stress) on the steerer tube.
However, I would assume that the F in this case is minimal unless you have a poorly fit bike, as most of your weight should be going onto your elbow pads, and the torque that they can exert on the steerer tube would be minimal, since they're close to it (so it would be like F*.1 at most).
I would think it woudln't really be an issue. Any steerer that would actually crack or similarly fail would be too weak for road use too, I'd imagine.