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Originally Posted by Grant-53
Whether the rider leans forward or to the rear the idea is to reduce the height and frontal area. The only concern with a rear leaning arrangement on a scooter is F/R weight distribution. Just make sure the tail is long enough to keep the center of pressure behind the center of gravity and enough down force on the front tire for good handling.
The Sym 250 was rated at 96 mpg and the 150 rated at 90 mpg likely due to the fairing. In project after project the results seem to be +50% improvement from streamlining and 50% from hypermiling.
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Scooters are already feet forward and low but the cvt drive gives up some efficiency in the rubber belt and variable pulleys compared to a chain. Standard bikes such as the CBR250R or Ninja250 dictate a head forward lean if you want to reduce frontal area and height of the side CoP. Alan has chopped the frame and added length to the swing arm of his second Ninja to get a lower, feet forward position. Moving back on the Ninja always involves reworking all of the cables and lines and shift linkages. An updated Rebel300 would be an excellent starting point for a high efficiency streamliner with it's already low seat and laid back foot forward ergos and wouldn't need any of these advanced mods.
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A motorcycle has two wheels stuck to the ground. It is not an arrow and doesn't gain it's stability from having the CoP behind the CG. In fact, the optimal place for any side lift from crosswinds to act is centered on the steering head as proven in an experiment where a team tied a string to a bicycle at various places and found that when tied to the steering head, the bike perfectly self corrected for any reasonable side loads without any rider input. When tied to the seat post or rear of the luggage rack, the bike was easy to pull off course.
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I would have to see a log on any Sym 250 to believe a standard rating of over 90 mpgUS.
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