Originally Posted by
rsbob
Yesterday I weighed my steel ‘86 Bianchi Campione de Mundo and it came in at a ‘very svelte’ 25 lbs. Combine that with racing gears and the slowest of slow tires, Gatorskins and this girly man has one heck of a time pushing that bike as fast or far as my carbon Bianchi with GP 5000 tubulars, weighing 8 lbs less. By your criteria, I must be worthless and weak, but I can certainly live with that just fine. If you would like to take my 86 for a spin, you are more than welcome to enjoy the beauty of Columbus steel.
Lance would approve.
Weight has an almost negligible effect on speed except in the wheels but the frame can be 5-10lb heavier and if you calculate the bike should only be something like a few tenths of a mph faster in the flats. Even on hills it makes a bigger difference but thanks to the rolling of the wheels which takes away much of the work of moving the weight small differences in mass like that are nearly inconsequential.
Yet a bike that is 5lbs lighter than another bike all else being equal is going to be faster and the weight is a good proxy indicator for the extra speed even though the weight itself changes little. This is because a bike that is lighter is
stiffer. The lighter means that the material can be made to flex less while being thinner hence the weight savings and it's that flexing less that allows more of your power to spin the wheels as opposed to moving the frame. So the weight is a good measurement for how fast a bike will be but not because it's lighter, but rather that lighter bikes are more efficient and thus faster.
The difference is often amplified because lighter bikes are also more expensive thus nicer so all the componentry will be better. You have better groupsets, as I said lighter wheels too and these items all put together also help to make the bike faster assuming same rider and same power output.
Aero makes a huge difference though. Maybe not the frame or the bar but your body position especially does. Try getting on the drops or if you have a flat bar bike just lean more forward you will go for same effort about ~2mph faster depending on speed.