How to enlarge wheel hub bore?

I picked up a set of 17" ND Miata wheels for $100 yesterday. I'm a wheel whore and a bargain fiend......it's a curse. My intent is to modify the wheels to fit my ND and my MINI. A MINI needs a 56.1mm bore and the wheels are 54.1mm.  In the past I have taken a router to wheels and successfully enlarged the bores, but it results in a 57.3mm bore, OK for VWs. I've never worried about bores not being hubcentric, so I'll cut them if I don't find another method. Do any of you have any neat ideas about other methods to get a bit better fit? I don't have access to the really big lathe that I did 20 years ago to machine wheels precisely.

Edit: The 57.3mm is a result of using a 1/2" finishing bit with a 3/8" bearing.

I may have figured out how to cut the wheels to 73.15mm and use regular centering rings. A 3/8" slot cutting bit should be real close, then a 45 degree chamfer bit to finish the edge. Still open to other ideas though.

Know anyone with a CNC mill or router capable of machining aluminum? At the one end is taking them to a wheel or machine shop. At the other end is using a file, and somewhere in the middle might be using a die grinder or really aggressive sanding drum. These latter suggestions are only because you said you don't car if they remain hub-centric.

Dingle ball hone for small engines?

I'd get a hole saw that is a loose fit, wrap it with 36 grit paper (a length of sanding belt perhaps) to be a slip fit, then spin that to hone it to size. You're looking to increase the radius by 0.040". Should be doable.

How about something like a small ridge reamer for a moped/mower engine?  

Disclaimer: I subscribe to the belief that most mass-production wheels are effectively lugcentric, and I run flat wheel spacers with zero noticeable vibration at interstate speeds.  I also tighten my lug bolts in successive 5lb-ft increments (okay, not really, but I do not tighten each one completely before installing the next)

Some random ideas just as a brainstorming exercise:

• Add a sleeve to the outside of the 3/8in guide bearing so it ends up 2.00mm smaller diameter than the 1/2in router bit.  IOW, end up with a 10.7mm OD bearing for a 1/2in (12.7mm) bit.  Coincidentally, .40 S&W cases are 10.77-10.74mm OD, but you'd need to shim from the 0.375 bearing OD up to the 0.40 case ID.  Maybe just wrap the guide bearing with aluminum tape?
• Get a template with a 56.1mm ID hole (like maybe a wheel spacer?), center it precisely over the existing wheel bore, clamp the template in place, then cut the wheel using a guide bearing which rides on the template and is exactly the same dia as the cutter dia
• Custom grind a router bit (b/c it is just so totally easy to precisely grind carbide at home; however there are companies which resharpen or custom grind endmills and cutters, and they can be surprisingly not too expensive so long as you don't require some funky flavored coating).
• Metric router bits exist (both cutter diameter and shank diameter).  Metric bearings exist.  Presumably somewhere in the universe (outside the US) it is possible to simply buy a combination of router bit and guide bearing with a 2.00mm difference

In reply to Oapfu :

I like your second and fourth ideas. Next time I'll consider them, but this time I went at the wheels with a 1/2" finishing bit and 3/8" bearing. I took two cuts, which nominally would put the finished bore at 56.3mm because I piloted off the 50mm bore at the center cap(the black area). Routers aren't all that precise, so the finished bore is about 58mm. I've run wheels without centering rings before without any ill effects, so I'm not worried about these rims not being hubcentric.

Dusterbd13-michael said:

Dingle ball hone for small engines?

Honing aluminum suuuuuuuucks.  I tried this to make ZX2 wheels fit a Sentra.

Don't worry about hubcentricity, that's just for ease of installation and I don't even think it helps there unless you have a German car with wheel bolts. I think your router technique is just fine.

In reply to Keith Tanner :

The Miata wheels will most likely end up on my MINI. There's enough gap that they don't bind, or get seized on, but close enough that the wheel bolts go in normally.

In reply to DeadSkunk (Warren) :

The other pictures of router work I've seen, looked WAY janky on the surface finish, from chatter. 
Your finish gives me hope!

Any suggestions on keeping the chatter/gouging down to a minimum?

Router. Good ear, eye, and beard/arm hair protection is a must. 

In reply to 03Panther :

I used a 1/2" bit, so the perimeter speed is less than bigger bits, and it's easier for the router to maintain speed. The other things is to focus on keeping the router squarely on the wheel mounting face and go fairly slow. The wheel pictured is the nicest one. I had the bearing come off once and I gouged the wheel, and the depth collar slipped another time. It doesn't matter in the end, but I would have liked all four wheels to look like the one pictured. I'm two for four.

Byrneon27 said:

Router. Good ear, eye, and beard/arm hair protection is a must. 

I had the wheels supported on two sawhorses that were tied together by a couple of pieces of scrap wood. The pieces were angled so the wheel got forced into the wedge and wouldn't move away from me. Most of the chips just went out the center hole and fell to the floor. I did wear a grinding shield, just in case, and I removed my hearing aids and wore ear muffs.

I'll add that I started with a new bit from Menards and it shows visible wear after doing four wheels, eight cuts. It was $13 or $14. Still good for more wheels, but not good for finish cabinetry any longer. I picked the router up at the Habitat-for-Humanity Restore for $10 IIRC. So all in, I've got the wheels ($100), paint ($13) and a router bit ($14). Pretty good for a nice looking set of 17x7 wheels that weigh 4-6 pounds each less than the ugly, and heavy MINI S-Lites. Now to find some cheap autocross tires.

Keith Tanner said:

Don't worry about hubcentricity, that's just for ease of installation and I don't even think it helps there unless you have a German car with wheel bolts. I think your router technique is just fine.

The only concern I ever had about hubcenctricity was balancing.  You'd have to make sure that whoever balanced it located the wheel on the machine via the lug nuts or the center cap hole.