Originally Posted by
tjspiel
I'd like to see the scientific inquiry showing that derailleur systems are less efficient if you can point me in that direction. Like I said before, everything I've seen to this point says the opposite. I'm looking for something that talks about more than just the pros and cons of various cog sizes.
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.
Originally Posted by
tjspiel
My commute is 75% flat, especially the part that's in traffic. I spend the majority of time in the middle range of my gears. I can usually start pretty easily in any gear I happen to be in even if it's not the ideal one. Not always, but most of the time. Being able to quickly transition from lowest to the highest gear has almost no value since I would rarely choose either one for any part of my commute.
You might feel differently if it were easier to shift between widely dispersed gears (it doesn't necessarily have to be THE lowest and THE highest gear...just as easy to use 2 and 7 or 3 and 6 or whatever tickles your fancy...once you get good with the shifter you just slap it and it magically goes to the gear you want). Personally if I were going to be starting in less than ideal gears I'd sooner take a singlespeed bike than a derailleur (why bother having them if you can't use them to the fullest?). To each his own.
But I agree that it's not
that hard to get into the right gear with a derailleur before stopping...it's just that I'd rather be focusing on braking, filtering, whether I can beat the yellow, picking my nose, etc. I also often change my mind about what gear I'm going to start with once I'm done picking my nose and have time to inspect the condition of the intersection (amount of potholes, etc) or if I decide to take a shortcut (right on red, maybe move to left lane for an upcoming turn...or maybe even run the light if no cross traffic).
Originally Posted by
Sixty Fiver
Those same mechanical engineers you like to reference also have recommendations on chain lubrication requirements and when it comes to things like this, Sheldon Brown's credentials were rather excellent.
Yeah, well there's no substitute for trying it yourself. Sheldon knew that very well: Some of the stuff he did should make anyone cringe, but there's no arguing with success.
As to the lubrication (if we'll ever let it die), some of the engineering requirements also relate to cleanliness. If we listened to them we'd have to conclude that roller chain is simply unsuitable for exposed bicycle use.
Originally Posted by
Sixty Fiver
It would be interesting to test this to see just how many more miles one could get out of a drive set up like this... my winter bike runs a 40:20 and after an entire winter has no measurable chain wear. I am using a KMC 710 1/8 and have found these run for an extremely long time and only start to show minimal wear at 6000 km after some pretty extreme use.
Might have to mark the sprocket the next time I pull off the wheel and figure this chain will take me through summer rains and well into next winter... this is a plus with an IGH and a good chain / sprocket as the chain life is far better than any derailleur equipped bike that has to handle the same conditions.
Let us know. The one I'm building is 44/22 (not enough clearance for 46/23 or 48/24), but this one's a recumbent so the carbon frame will probably delaminate before the chain even begins to show signs of wear.