I think the heaviest is my Raleigh Superbe at ~40# my Twenty weighed close to that before I started modding it. I would guess it is a good 10-15#'s lighter now with alloy wheels, alloy seat post and a leather Brooks.

Heavy bikes are durable and will handle some pretty rough roads a lot better than the lightweights, the trade off is speed and acceleration, but once you hit the downhills heavy bikes rule

Aaron