[QUOTE=jschen but hitting 52 MPH on a 15% descent shouldn't be too hard. [/QUOTE]
Eh? That's 83 Km/h

Fairly hauling arse!
The best I've done is 72 Km/h on my road bike in the mountains, but commuting (flat but: lots of traffic and loads of traffic lights) my best is 46Km/h.
Steve.