You may want to consider the following products for coating your wheels.
Endura EX-2C. It is an aliphatic polyurethane and is used for the protection of all types of transportation equipment (land, sea & air). Priming is with EP-2C primer/sealer. Blast first with 70 mesh grit to obtain a ½ mil to 1 mil blast profile. I used this on my KVA frame and it worked really well. It is a very hard coating. It has high gloss and color retention and outstanding resistance to chemicals, abrasion and impact.
Another coating you may want to consider is PSX-700, which is distributed by Ameron. It embodies the properties of both a high performance epoxy and acrylic polyurethane in one coat. I became interested in this coating as it was claimed by Ameron that it could be applied to aluminum with only a solvent wash. Coatings will not normally adhere to aluminum without providing a blast profile, or treating the surface with Alumiprep and Alodine (as used in the aircraft industry) to provide adhesion. Blasting will distort thin gauge aluminum and is therefore not always practical and the Alumiprep and Alodine process can be expensive. As I was skeptical about the claim that only a solvent wash was required I asked General Paint to run some adhesion tests on aluminum test panels, which revealed exceptional adhesion. (1700 – 2000 pounds on pull tests) on a surface that was only solvent washed. I did the same test on a surface that was treated with Alodine 1201 and got pulls of 1500 – 1750 pounds (also very good). PSX 700 is expensive (about $204/gal) but you do save on preparation costs. This is the only coating that I have found that can be applied to aluminum without blasting or surface treatment with the two products below. PSX-700 will not chalk (as an epoxy will) and maintains a good gloss. It is probably not quite as good for impact as polyurethane.
Quite often aluminum wheels are powder coated, as you probably know. If you go with powder you may want to consider a polyurethane.
Alodine 1201 and Alumiprep 33 can be used for thin gauge aluminum panels such as aircraft skins where blast cleaning would result in distortion. The Alumiprep is a phosphoric acid based cleaner, which produces a chemically clean, and corrosion free aluminum surface. The Alodine is a chrome conversion coating that offers the best affordable substrate for both paint adhesion and corrosion resistance. You do not need either of these two products if you can blast the surface to get an anchor profile without running the risk of distortion. Blasting would not distort an aluminum wheel.
I have data sheets on all the above products and can fax them to you; however, they are available on the net or from the industrial coating suppliers.
Please feel free to contact me if I can provide any further information on the above products or process. Hope this gives you some ideas.