The BB height is equal to the wheel radius minus the BB drop. 700c wheels have radii that range from 33 cm for a real skinny 19mm sew-up to nearly 35 cm for a heavy-duty city tire. Most road bikes will fall into the 33 to 34 cm range. Just about the most BB drop is 8 to 8.5 cm, found usually on DeRosas and Richard Sachs. Rivendell may have a few that are this deep, as well. The old favorite steel Treks were usually around 7.5 cm. I have one of those Treks and I've borrowed OFG's latest DeRosa, and I do like the feeling of straight, powerful pedalling I get on the DeRosa. My Masi and Mondonico are each around 7.5 cm. I like them both very much.

I would try to get a frame design with that 8 to 8.5 cm BB drop. It's harder to design in the smaller frame sizes - the down tube wants to run into the front tire, if the head tube angle is made on the more relaxed side. But if you're going custom, discuss it with your frame builder. There might be some important reasons not to go this way. Its true a low BB (large BB drop) can result in more pedal strike in corners, but I've never had that happen. Guess I'm just not enough of a hammerhead.

Road Fan