Originally Posted by
chucky
This study reports a 5% increase in efficiency for bigger cogs and a 2% decrease from standard cluster to IGH with small cogs:
http://www.ihpva.org/HParchive/PDF/hp52-2001.pdf
So if you combine the two the net increase in efficiency is ~3% for a properly configured hub gear (maybe not quite that much because you can't get IGH cogs
that big...I estimate it's closer to ~2% for stock cogs).
Other studies have reported similar results.
But doesn't it say that "Hub gears are generally about 2% lower in efficiency than derailleur-type gears" ?
(Item #2 under conclusions).
That's pretty close to the number I've heard before.