How would go you about finding the centre of the wheel? Would you have to put a tool in the chuck that had the same diameter as the hole and then jog down & zero the axes or is there another / better/easier/more accurate way of doing this ?
Normally you would use some form of edge finder, position approx centre then move one axis until you find the edge and zero the DRO, jog the opposite way and find that edge and type /2 in the DRO and it will give you exactly half of the distance you have just moved. Move that axis to zero then repeat for the other axis, you have then found the centre of the hole
You could also do as Alenz said above and cut a hole in some material so you can drop the wheel in and clamp it, using the circular pocket wizard would let you do that easily.
Hood