Originally Posted by danfoz
If going for an aero rim it's important to check the width. If you enjoy running 23 and/or 25mm tires, according to a white paper done by Specialized the aero benefit on a 19mm wide rim is almost completely negated due to the turbulence created by the lightbulb effect on a 25. If running a 19mm wide aero rim, to extract any benefit a narrower 21-22mm tire will be needed. If running a 23mm or wider tire on a 19mm wide rim it makes more sense to stick with a low profile rim, unless of course riding cyclocross where a deeper rim doesn't get bogged down in the mud as easily.
imo if investing the money why not just go to the newer paradigm of 23mm wide rims. Wider tires spread over a wider rim feel better, handle better, and supposedly roll faster. One doesn't have to go with one of the uber expensive all carbon models. Something like HED's Jet5 express offers almost all the benefits at a lower price - alloy breaking surface, 23mm wide rim, aero performance, a weight range that wont hold anyone back, and at a relatively competitive price (for the product received). There are others. After riding the last couple years on wider rims, I'll never go back to the old 19mm's.