I've had the same problem a couple of times when changing out the rear tire. The wheel was not fully seated onto the bevel box. What I did was cut a metal tube slightly smaller than the width of the brake fitting that goes between the spacer and the swing arm, then put the axle through the wheel, the spacer, and the tube and then through the swingarm, and then put the nut on and torqued it down a bit. That compressed the wheel fully into the bevel box splines and after doing that the brake would fit just right.