IGH vs Derailleur on folding bike
So I have this debate with myself...
IGH will be less maintinence but will also be heavier.
Derailleur is more maintinance but is lighter.
The thing is, folding bikes are carried more often than regular bikes, and so being light for a folder is much more important than being light for a regular bike.
So are IGH's on folders the best idea? Benefits of IGH seem to be most for heavy commuter bikes
Efficiency is an Issue with IGH
One issue that has not been raised is efficiency. I designed the drivetrain on the Xootr Swift Folder. We considered a variety of IGH options and derailleur options. We made some measurements of efficiency. (This turns out to be quite hard, but we ended up running a series of human experiments in a hill climb -- about 10 trials with each set-up and fitting an implied efficiency to the performance data.) Some of the "speeds" in an IGH are very bad, as bad as 85% efficiency. By comparison a derailleur with a clean chain should be in the high 90s, and even with the grungiest chain is still probably better than 95%. A 10 percent difference in efficiency is a really big deal. You won't notice it on a flat bike path commuting 2 miles to work. On a brisk ride with your friends, you'll really suffer.
One important caveat. Most iGH have one "Speed" that is a direct drive -- just locks the sprocket to the hub. That one is very efficient, even slightly better because there are no derailleur idler pulleys. However, I found it was often an inconvenient speed. (On some three speeds it's the middle one, though, which is great.) Conversely, some speeds are really, really bad as they involve all the possible planetary gear pairings to achieve the target ratio.
Note that the poor efficiency is intrinsic to the planetary gear design -- each gear mating is 95% efficient or so, but they are stacked up on each other multiplying that loss twice or three times. The quality of the hub matters only a little bit -- a Rohloff might be marginally better than some anonymous inexpensive hub, but that difference might be a couple of percent, not 10 percent.
An option worth considering if you ride mostly modest terrain is a single speed. We created that option for the Swift as it simplifies everything and makes the bike a lot lighter.
Originally Posted by adlai