Except in mountain bike racing, no technical innovation regarding anything used, worn or carried by any rider or license holder during a competition (bicycles, equipment mounted on them, accessories, helmets, clothing, means of communication, etc.) may be used until approved by the UCI executive bureau.

So mountain biking gets a pass?

Not legal

“We suspect extreme designs may not pass muster,” VeloNews observes. We suspect it’s a moot point. The relationship between speed on a mountain bike course and bike design is far more subordinate to non-design factors, including rider skill, terrain and weather conditions, than with a road bike — which is as it should be. We would like an example of an “extreme design” that would actually aid a downhiller or even XCer (beyond today’s designs). The one biggie — suspension travel — has been pretty much maxed out within the laws of physics. You don’t necessarily gain speed through more travel or greater aerodynamics or even light weight: The thresholds of over-design (e.g. stupid light) have already been tried to failure point. And that’s why the UCI hasn’t really come up with anything in the way of regulation. They haven’t needed to. But you never know. Someone could figure out a way to fill a frame with helium maybe. Or devise an anti-gravitational bottom bracket. Or tires that have wings.

Perfectly legal

The other factor here, alas: The money at stake in mountain biking competition is so puny compared to the road scene. That’s why the best mtb racers have been going over to road. It also might help explain why the UCI hasn’t been particularly motivated to get into mtb oversight.