Late comer here .... just read thru this post for first time. I had the same thing happen earlier this year when changing tires. Had that extra gap like NITRO was having. Ended up doing what Ricky-D suggested by inserting the axle in part part way thru .... put the wheel on the axle and then slid the wheel all the way into place .... then pulled axle out a few inches to install caliper bracket, etc. I remember the spacer being the culprit as it wasn't exactly perpendicular with the housing and the axle trick lined every thing up ....
That is the way I always do it.
MP
It never ocurred to me that one might attempt assembly without the axle inserted, I should have caught that. Hoser