Originally Posted by
FBinNY
Sorry, but this last bit was just too much.
The amount of energy lost to friction in the freewheel clutch is so tiny as to be meaningless. In any case it's much less than the amount of energy lost to friction in a chain drive.
If anyone doubts this, I suggest you set up a freewheel bike (single speed or derailleur doesn't matter) and a fixed gear bike as well as possible. Bring both wheels to the same speed, and let go of the cranks. Does anyone want to bet a couple of beers which coasts to a stop first?
This last claim is why I responded, but the first part about momentum in the legs is equally flawed, maybe more so. Our legs are not well oiled machines and it takes considerable energy to work them, even without producing any power. Riders of fixed wheel bike know this because they need to work even on descents, not to power the bike as much as to help keep the cranks turning and not be bouncing around as they turn.
We run into parallel issues which may be instructive in the auto world. Those looking to maximize fuel economy will either clutch or shift to neutral and "coast" down hills. BITD Saabs used to have an overrunning clutch so they could "freewheel" down hills and save fuel. The problem with freewheel descents is that the engine braking is important in that it's drag helps the brakes and prevents brake fade, which is why the practice is reserved for fuel economy contests.
I knew someone would react to that last bit about the sound of the hub.
It was intended to be rhetorical, but you know it is literally true to
some extent. As for your experiment, we might be surprised. I don't have a computer on my FG to check speed, but I tried it just now, and was surprised by how the FG compared to the regular bike I had in the stand and tried first. (BTW, I'm really annoyed by how noisy the new aero wheel is, but it's so sexy looking, I forgive it).
Not sure what your objection is to the notion that it's an advantage of FG to sustain momentum in the legs - an advantage with respect to moving forward and maintaining speed. Yes, the disadvantage of fixed is that one usually has to work to slow down or maintain control on descents, but that's not a flaw of the drivetrain system as such. The purpose of a drivetrain is to propel one forward, not to slow one down, but I will concede that it's usually a good thing if it can help in the latter regard, too. I
know this, because the most exhausting ride I ever did was the NYC Century on the FG (and not even the whole thing). Not because there were any challenging inclines - in fact, the little hills were a relief. It was all the STOPPING that killed me.