Just wondered if anyone here knew the answer, I couldnt find it via google, when you look at high end track bikes, eg hoy's why are they using internal BB systems not external, if external are supposed to be much stiffer?
Q factor?
Q-factor.
Is it to do with the lack of single ring chainsets for external BBs?
I assumed (maybe wrongly) if the frames, bars etc are all custom for the GBR team, a low q factor single ring crankset cannot be that hard to produce
not sure why, but the Campagnolo Pista components don't seem to have changed in years and the costs of tooling up for new chainsets might be prohibitive.
Consider that the power output of a decent track sprinter is huge, cheap cnc one offs might be fine for most people but forging is far better, but tooling is expensive.
Couple of guys at the track have planet X's with external BB's.
if you want one they are availble..
[img] 
[/img]
[img] 
[/img]
Narrower Q factor would minimise lateral forces on the BB which could allow for more direct power transfer, so it kinda makes sense.
Lighter, more efficient, and they work.