Originally Posted by
kensuf
Wheel flex definitely. I've got a set of ksyrium elite's that just haven't been "right" since a guy stuck a foot in them during a crit last year, and they now flex quite a bit and I lose a lot of power. I had a set of custom wheels built up for myself for Christmas and the difference is night and day.
The only way you lose power to wheel flex is if they flex into the brake pads. Torque flex from pedaling action will result in no loss at all -- well I guess it would in the CF-spoked wheels, but it's going to be so small that it's not even worth the pixels it takes to mention it.
Crankarm, seatpost, and handle bar flex are all also going to return any flex to the system. No losses.