Now loosen the rear axle...
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And loosen the locknut (on both sides naturally!)
IMG_0121.jpg
Move both adjuster and locknut all the way to the back (both sides!!)... Now you should be able to push the wheel further forward (towards front of bike) to get the chain slack needed to change the sprocket...
IMG_0122.jpg
Remove old sprocket...
IMG_0123.jpg
See the difference...
IMG_0124.jpg