Bicycle Mechanics - Drive train efficiency?

I have been reading about internal hubs recently, and they seem to have some attractive features. The downside seems to be inefficiency. MY LBS guy says the Nexus hubs are 90% efficient, and I think he was referring to the Nexus 7 hubs. Does anyone know how much different the Nexus is, and whether the two models of Nexus 8 vary in efficiency? The Rohloff website, as I interpret it, says that their drive is 91-97% efficient, depending on gear. What info on efficiency does anyone have for these and other drive systems? Just because a system loses 10% of energy, I don't know that it is worse than a derailleur system, because I don't know how efficient the derailleur systems are, and whether their efficiency is a function of the chainwheel-cog combination, nor whether derailleur system efficiency varies by model.

supposedly, derailleur systems are more efficient given two conditions:

-you're not making the chain bend across (such as when you use the small chainring in front and small cog in back, or large-large)

-you keep it clean

I have not heard that friction thing before; I tried a web search but came up empty.

But I do have three thoughts concerning the Nexus hub; first is the hub is quite a bit heavier then a standard derailleur and hub system, thus you have more weight but it's all bad weight because it's rotational whereas the just the hub and chain are rotating on a regular system.

Second is that the Nexus system would be more prone to mechanical failure of which you would probably be forced to walk, PLUS most backyard bike mechanics will not be able to take it apart and fix it themselves.

And third you not only have the intial cost of the unit, but maintence cost as well.

The standard derailleur system is a lot less complicated, and in the cycling world simplicity is the best way to go because should you breakdown 60 miles from home you can more likely field repair it completely, or at least enough to ride home. This is one of the reasons I still ride on a friction system.

But I do have three thoughts concerning the Nexus hub; first is the hub is quite a bit heavier then a standard derailleur and hub system, thus you have more weight but it's all bad weight because it's rotational whereas the just the hub and chain are rotating on a regular system.
.Well, not really. They are generally heavier than the der. system, but the hub is at the center of the wheel, so it's not rotational weight.


Second is that the Nexus system would be more prone to mechanical failure of which you would probably be forced to walk, PLUS most backyard bike mechanics will not be able to take it apart and fix it themselves.Why more prone to failure? Any studies to back this up? According to bike expert Sheldon Brown (http://www.sheldonbrown.com/internal-gears.html), the opposite is true: "Internal gear hubs are more reliable than derailer systems, and require much less maintenance."


And third you not only have the intial cost of the unit, but maintence cost as well. See above regarding maintenance.


The standard derailleur system is a lot less complicated, and in the cycling world simplicity is the best way to go because should you breakdown 60 miles from home you can more likely field repair it completely, or at least enough to ride home. This is one of the reasons I still ride on a friction systemI agree with you on the friction system. But regarding derailluers, they fail all the time. Ask a mechanic how many mangled derailluers he sees.

Bottom line is, you there are a lot of factors to use to decide on which system works. What type of riding you do is probably at the forefront.