At first glance the Birdcage looks like a fairly conventional “aero” style rim, but there is more to it than that. Traditionally, the greatest flaw in “aero” rims has been the valve hole. “Aero” rims position a lot of very efficiently utilized mass in the base of the rim to support the spokes and give the rim good strength, then a huge hole is drilled through it for the valve stem and a massive weak-spot is created.
