We had our CVR PCA meeting last night and the Northeast regional BBS representative gave a presentation. Of particular note was the damage that powder coating does to a wheel if it's done outside of the initial manufacturing process. In other words, if adding clear coat, anodizing, or even powder coating is factored in when the wheel is made such that the chemistry is planned out, then it's not a problem. But people that take delivery of a wheel and then send it out for powder coating are going to see a 30% degradation in the structural integrity of the wheel. The way I understood what he said - it was like heat treating something in the manufacture and then "undoing" it by baking on the powder coat. I didn't quite understand how that differs from heat cycling the wheel on the track - I just don't know much about the powder coating process.

Anyway - I had never before heard of negatives of powder coating metal and even wonder if this applies to things like roll bars. Just a heads-up to all...

P.S. He rolled his eyes and said "Honestly, I don't know why anyone wants black wheels in the first place - if it's to make the car look racy, it isn't working because all race cars have silver / aluminum colored wheels..."

 

I was under the impression that the powder coating process of wheels doesn't necessarily include heating. I've had a few sets of wheels powdercoated with a spray-on electrostatically(sp?) charged paint, and was told that if it's been dried in an oven, it's going to melt next time it's heated (i.e from the brakes during track time).

This was ~10 years ago though, perhaps the technique has changed.

 

Yah, as I mentioned in my post - I didn't understand how the process could damage the wheels by 30%, yet normal track heat cycling doesn't. Just a heads-up from what the BBS guy said. I think the point is to be aware, ask questions, and also reconsider "why" spend money on aesthetics especially if it can damage your wheel. He also said if you damage a wheel, leave it alone or replace it - don't fix it because even if you make it look aesthetically correct, it structural integrity is gone (ie: Bent rim straightened out). On things like curbing - I know from my own research that to bondo, sand, paint, and clear coat is a fine way to go.

Out of curiosity - I just searched on "powder coating a wheel" and the top site had this to say about the process (so now I understand why BBS says not to):

The powder coating process involves curing coated parts in a 400 degree oven for 10 to 20 minutes. The results are simply amazing and very durable.

Oh, another point he made that I forgot - he said the reason race teams leave wheels silver / raw is so they can detect cracks. On a silver colored wheel if a crack forms, you can see a black line from brake dust collecting in the crack. If you have black powder coated wheels you will never be able to tell.

 

woow...good post!!!!

 

From what I know about powder coating, it should only be harmful to forged wheels. This is because after forging, the aluminum is annealed at a certain temperature and baking the wheels again at too high of a temperature can alter the structure of the aluminum and make it softer. However, there are some powdercoating shops that use lower heat ovens and claim that it is perfectly safe for wheels. Supposedly, this doesn't apply to cast wheels, although I'm not sure. I think the main problem is that a lot of powdercoating shops don't use the proper methods for prepping and coating wheels. A number of things can damage them, both before and after the powdercoating. If the wheel is chemically stripped instead of bead blasted, that can weaken the aluminum as well. Just make sure you talk to your shop and make sure they know what they are doing.

 

Another issue is warranty. Once you change anything with the wheel, you are on your own. I think the BBS guy said they have a 3 year warranty on the wheel - that's valuable to have.

Over at RennList there's a serious metalurgical discussion going on about alloy, heat, etc. General scientific agreement that you don't want to do anything harmful to something as important as a wheel especially if you are tracking (why chance it). Also some theories that some processes may not be too harmful - but one powder coat vendor even suggested that a thick powder coat can "hide" internal cracks in a wheel, especially the thin spokes, which is not a good thing to have - in theory, no warning (ie: visible small cracks) and you get wheel failure when the small cracks become big.