[jackmott42]

Carbon fiber bikes have two main properties that can affect performance:

1. they are a little lighter. This doesn't matter nearly as much as most cyclists think, but it does matter a bit. If you race competitively in the mountains, you might care.

2. There is more design freedom for shaping them aerodynamically. This makes a bit more difference than weight, and if you are competing you definitely want it.

[timeon]

> doesn't matter nearly as much as most cyclists think

Weight matters also off-bike. For example if you need to carry it upstairs daily. So it can matter even for people that do not race.

[plorkyeran]

Even just loading a bike onto a car rack is a pretty big difference. I don't think I'd pay for carbon if the only benefit was it being easier to carry, but it is a pretty big benefit.

[PretzelPirate]

I used to live in a 3rd floor walk up in NYC. I appreciated my carbon bike. I even considered buying carbon wheels.

[habnds]

they can also be stiffer in some directions and more flexible in others, which is a huge underestimated advantage compared to metal bikes.