I got a 21 with chrome hub and 25 mm bearing for my 05 fxsti, changed the 25 mm bearing to 3/4 to fit my axle and fork legs...here's what I had to do. The bore depth for the 25mm wheel was the same on the right side as the 3/4 was, the bore depth on the left side was .100 shallow on the 25mm...so I made a new inner spacer that was .100 longer than the inner spacer off of the 3/4 wheel, then machined a new outer spacer for the brake side that was .100 shorter than the spacer for the 3/4 wheel to make up for difference of the bearing setting a little farther out of the hub. The 3/4 bearing will set about .050 farther out of the hub than the 25mm bearing does.

So you will need 3/4 bearings a new inner spacer and a new outer spacer for the brake side...pretty easy really. Hope this helps some?