This may not be the right place to post this, but WTF. Our brother's post on wide-bandwidth gear ratios got me thinking a lot about how changing out my front sprockets from 14 - 15 (stock) - 16 tooth affects fuel efficiency. I can't bring myself to spend major smucks on a new gear set, but it isn't hard to change out front sprockets. So I'm going to stay with the sprocket approach and tailor my scoot for a particular ride. But looking into it further, I learned that the Duke has nearly identical fuel efficiency as the Enduro R even though it comes out of the stable with a 16/40 sprocket combination. And then last week I met up with a dude that owns a Duke, and I asked him some questions about shift points. It turns out that my experience with the 16-tooth needing to down-shift at ~52mph as apposed to 42mph with the 15-tooth on my 690e was pretty-much right on. He says that particular shift point is ~55mph on his duke. Note that both bikes use the same primary gear ratio. Just the sprockets are different. But it looks like fuel efficiency is at least somewhat if not largely independent of a given RPM the engine is running at. Engine wear is obviously highly dependent on RPM, but apparently fuel efficiency isn't. But my current theory goes like this:
14-tooth front - For hauling most royal butt on all terrain that isn't paved. (mega power wheelies in 1-4th gear I think.)
15-tooth front - A good general purpose compromise. (power wheelies 1-3 comfortably)
16-tooth front - For hauling most royal butt on pavement, gravel, and well-defined trails (still got power wheelies in second. Maybe third. Haven't tried it)
So what do you guys think? The real question I'm pondering over is if there's any difference between (say) adding a tooth on the front versus removing three teeth from the back sprocket. I don't think there is but I've been wrong before.