Wow. If you read what I wrote, I was discussing whether powder coating has the potential to weaken a wheel in general, not what is responsible in this particular case. I have not dismissed the potential for media blasting to damage wheels.

When you say that "physical failure analysis has been done", you are talking about failure analysis of a different case, which is not an automotive wheel. While it proves that media blasting has the potential to initiate cracks in aluminum in general, It does not prove that it always will initiate cracks for every process and every alloy and temper, and it certainly does not prove that it happened to this particular wheel.

The original poster's wheel? We don't even know whether it was powder coated, or media blasted. Without failure analysis of that wheel, we don't know for sure how that wheel failed.

Did your research into media blasting extend to changing different parts of the technique to determine whether there is a safe way to perform the process? Different air pressures, nozzles, media, re-using media vs not re-using media, etc?

 

The logic is correct. You're just reading additional information and assumptions into it.

The statement: I smoke and I don't have cancer, therefore smoking does not cause cancer.
uses the same logical construction as the statement: I powdercoated my wheels and they haven't cracked, therefore powdercoating does not result in cracks.

Neither is a valid logical statement, because a single counterexample does not prove that a condition is never true. However, we know from science (not logic) that smoking generally does cause cancer, which is why it's such a good example to show that the logical reasoning must be flawed.

I'm sure that Steve can speak for himself, but I'm sure that he wasn't implying that because the logic is flawed the conclusion is false. That's also a fallacy.

 

I think you guys are missing something...


Wheels are a wear item.

 

That's a reasonable concept and may be worth some discussion, but there is still a big problem:

Catastrophic failure is not an acceptable way for a component to "wear out." With how little testing and data we seem to have on the as-sold wheels, establishing a life-based criteria is near impossible, so until we know more, the only assumption you can have confidence in is that any wheel can break, any time. And that's a bad way to drive, so it's worth trying to understand it a little more.
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I wish I knew more about metallurgy--PC introducing changes is a big possibility that could potentially be quickly ruled out or shown to be dominant.

Anybody know if the PC process has corrosive-type effects on the surface of the wheel? Rather, does it form points of crack initiation of any type due to the way it binds to the metal? Forged wheels have a great surface, which helps fatigue life, and speculating only by the name of the process, powder coating may produce a rougher, less crack-resistant finish, which would result in a less fatigue resistance for a forged wheel. If that's the case, it would probably matter less for cast wheels. Can anyone point to a good resource on common processes used for PC-ing?

 

I'm not the one jumping to conclusions here, so that fallacy you reference applies to the people who see a handful of PC'd rims fail and claim that all PC'd rims will fail (which is what the smoking comment infers).

When we have proven, scientific data showing how PCing is guaranteed to decrease the life of the wheel, then (and only then) will I agree that PCing is inherently detrimental to the life of the wheel.

There is a significant issue when comparing something that is nearly guaranteed (proven by scientific/medical data, double blind tests, etc) and something that happens to an extreme minority. It's too bad you can't (or refuse to) see the difference between the comparisons.

They are not the same. One invokes poisoning the well, one involves using a counterpoint (multiple, in fact) to show that there is a need to gather more data rather than jump the gun. In no way did I make the claim that PC'd wheels are 100% safe. In fact, I actually made the point that PCing wheels can be harmful to the wheels if the procedure is improperly performed. Again, I hope you can jump off the "PCing is bad because 3 guys have had wheels fail" bandwagon and approach this discussion fairly.

 

 

so...was the wheel powder coated or not?

While definitely [i]not[i/] cost effective, I had my buddy club qf's polished first by mag master then a year later ceramic coated by dan at speedway polishing and coating in orange, ca. The coating is applied and cured at room temp. Much stronger coating and thinner surface layer when compared to powdercoating.

 

Whether it's powder coated or not, track wheels should be checked before every event and changed after two years at most. The heating and cooling, not too mention the torsional forces put on the wheels while being heated on the track are tremendous !!!

 

+1

Sound advice and essentially my recommendation also. Phil makes his living mounting and unmounting race tires at the track so he most definitely knows of what he speaks.

 

Thanks for sharing your experience. What about for auto-x? Not as much heat compared to track days, etc. I wonder because of the OEM JDM BBS wheels that so many have used for this purpose. Would you worry about buying wheels that have been auto-xed on for "x" amount of year?

-Marc