UCI aero rule — BikeRadar
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UCI aero rule
edited January 2012
Could someone explain in very simple terms (if it's possible) exactly what the UCI's 3:1 rule is regarding aero bits on TT bikes?
It's just length:width ratio isn't it? As in if something's 1cm wide it can't be more than 3cm long although I think certain structural elements are excepted aren't they (hence why Spesh tried to claim the Shiv's nose was structural). Basically to cut down on large aerofoils all over the bike.
Yep. On the main triangle tubes can't be bigger than 80x80mm so if want use the full 80mm they must be at least 26mm in the other direction, 25mm being the narrowest allowed. Forks and stays can be 10mm but then they have to be 30mm in the other sense. You are allowed to fillet between tubes so that's why the likes of the P5 are much more than 3:1 round the head and seat tube. It's quite complicated in the details.