There is some play there - the chain carrier can slide on the axle and is attached to the wheel by the cush drive. _But_, the single sided swingarm bikes have an occasional problem where the cushdrive goes bad somehow (I've never owned a SSA bike so I'm not sure what the details on that are...)
Oh, and when the bike's a _proper_ bike, with a motor in it, they're called "rear sprockets", not "chain wheels"!
![Grin](http://ducatimonsterforum.org/Smileys/classic/grin.gif)
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