Also you reclaim the energy on the downhill. Mass doesn't matter as much as people used to think. (Hence no modern bikes being made out of drillium.)
The one thing where I suspect mass might matter is in the wheels. It's a huge difference between getting a heavy wheel spinning and a light one, and at least for commuting/recreational usage, most of that will be bled off as heat anyway.
The one thing where I suspect mass might matter is in the wheels. It's a huge difference between getting a heavy wheel spinning and a light one, and at least for commuting/recreational usage, most of that will be bled off as heat anyway.