Most people think powdercoating is fine and no one seems to be having any problems with it so it's your choice. My preference is to "wet paint" the wheels. The first ED 1M owner was told by the M folks that they used the 359 wheel because it was the strongest they had and that if he replaced them to go with something as strong.
I contacted BBS and they are concerned about re-heating the wheels past 190 degrees for more than 40 minutes.
So for me, it's not worth the risk when I can find someone to wet paint the wheel. Again, many think that the powdercoating concern is an urban myth and I am sure you will find someone that will tell you that the BBS folks don't know what they are talking about. If you really want to powdercoat, I would at least discuss it with the powder coating company. The operations I have seen will usually put many items in an oven and use a temperature and duration for ALL the items. They might be able to do your wheels at a lower temp and duration, but at least you have some info now.
Keep in mind that companies like HRE powdercoat all their wheels but the process is different. They cut their wheels from a solid block of aluminum. The stock wheels on the 1M are cast.
Anyway, here is the message from BBS that I received.
************************************************** ***********
We do not suggest ANY welding or heat used to cure the paint (limited to 90°C (194°F) for no more than 40 minutes).
Other than the base coat on the wheel that is powder coated, the rest of the paint process used on the wheel is a “wet” process.
When is comes to painting, the wheel should be treated like the hood of the car.
Regards,
Michael Cox
Aftermarket Sales
BBS of America, Inc.
5320 BBS Drive
Braselton , GA 30517
Email: michael.cox@bbs-usa.com
Web: www.bbs-usa.com
************************************************** ***********
Good luck.