I'm used to riding on a heavy bike. I recall plonking the rear wheel of one of mine up on a set of scales and holding the frame vertical: the scales read about 40-45kg.

I weigh 95kg (i.e. according to one of the forum titles here, I'm the featherweight end of the Clyde scale).

I have no problems travelling 80km in a day, I might walk steep hills but I'll pace myself and get to the destination, and on the flat I'll be doing around 30km/hr. Put a headwind in the equation though and I'll be barely keeping above 20km/hr.

The Bicentennial bikeway here in Brisbane comes to mind: riding that into the CBD, it's not uncommon to get a wind along the Brisbane River that slows me down to buggery. The only plus is that at least the wind is keeping you cool. (Perhaps a little too cool now it's getting to winter.)