Originally Posted by
jideta
I had 20lbs steel frame bicycle that felt like it was made out of lead. Super stiff and unforgiving; obviously I wasn't putting out the power this frame needed.
Lead is a really bad comparison, as it is heavy, but very soft. You could easily bend it and even tear chunks off it with your fingers.
On topic, I'd say there obviously is some difference in accelerating (and to a lesser degree, in decelerating), but that doesn't mean much on flats if you're not racing. I have done over 90 km on an old 20+ kg army bike that was built like a tank, and was fine. The weight actually helped to keep momentum when cruising; it took some more time to get up to speed, but it rolled very nicely.