Those wheels look to have been refinished, rather badly.
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The last photo does look to me like it shows chips in the original finish have been painted over. And of course they’re close to the alarming fracture. Might be a coincidence of course, there could be similar little flaws all over the wheel, but it makes me wonder if the spoke got hit. On the other hand, three wheels had fractures so it’s not one isolated impact that’s the cause.
Very glad the result wasn’t worse, as it so easily could have been. With luck like that maybe RIB_BBR could recommend some lottery numbers?
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This is quite a worrying situation. Not just for the driver when it happens but also other vehicles around. The trouble with alloys & I think we have all done it, they are really beautiful wheels & when we get a bit of curb rash we are all a bit embarrassed. Really speaking this needs to be properly investigated. I read an article many years ago where young drivers were swopping out their steels for cheap Chinese imports. Also a guy once told me that parts that have been powder coat can degrade the metal. He said sometimes water gets under the powder coating & starts to degrade the metal without any body noticing. Think from now on I’ll repaint rather than powder coat. Another point is how does this affect your insurance as you are supposed to declare all mods even if it’s a stubby aerial. Thoughts anyone.
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Thanks for this thread, some concerning info… i had a set of 2002 svt sport wheels powder coated at a reputable specialist, they looked superb but anywhere near a kerb and they marked / chipped very easily, maybe they where more brittle or it was just the powdercoating that was fragile, current wheels are painted as a result. Not sure about insurance tbh but a failed wheel would surely be investigated after a ‘serious’ accident
Couldn’t agree with you more. I read a lot of things about mods & the big one seems to be nd steering wheel. I must admit that with my nd that is the biggest disappointment, slippy, thin & big. I was thinking of the royal mod but have not got round to ringing insurance company. Quite a number of years ago my lad bought his first car, clapped out fiesta wouldn’t let me go with him anyway it had a boot spoiler & front spoiler. He had a bump, long story but they said they were undeclared after market mods eventually I persuaded them to continue the policy provided I removed them. Now to this day im very wary of mods & insurance well rant over.
An old thread I know, but this is how close I came to same outcome on a Silverstone track day a couple of weeks ago, two months after a track day at the 'ring.
All four wheels powder coated, and the other three showing signs of cracking too.
There but for the grace of god.
John
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Blood y hell, that is frightening.
A lucky escape by the looks of things!
I’ve heard of other cases where ally wheels have been powder coated and subsequently cracked. My understanding is that unless the baking temperature is controlled very carefully the process can adversely affect the factory heat treatment of the metal, causing it to become brittle.
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F*k 
I wasn’t aware this could happen due to powdercoating.
Hope you are alright and this is the only injury you have. What a shock this must have been.
I was contemplating between buying new bronze alloys or coating the original ones, but I think my mind is made up now on what NOT to do.
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Thanks. Yes, felt initially p!ssed off at reduced track time at Silverstone, then blessed that it hadn’t actually failed.
It’s BBR supercharged with an Onlins set up, we had 145mph on the long straight at the 'ring. Can you imagine if had failed then?! 
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Lucky ! I felt that when it happened to me db
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“My understanding is that unless the baking temperature is controlled very carefully the process can adversely affect the factory heat treatment of the metal, causing it to become brittle.”
Pretty much this. I’m not sure what alloy they actually use mostly, google says most wheels are 6061 which is handy cos it’s also what a lot of bikes are made of and that’s what i’m used to thinking about. And this is oversimple, but basically 6061 should be completely unaffected by 150 degrees, loses just a little strength if you heat it over 200 depending on how fast you heat it, but falls off HARD above 300 pretty much no matter what you do. Above 350 you can essentially lose the entire heat treatment strength benefits.
Most powdercoat is absolutely fine to bake under 200 (some epoxies have a range that goes up to 250 but should still bake fine at 200). High temp powders need more but mostly we won’t be having anything to do with those. And tbh while 250 hurts the wheel just a little, as long it’s done quickly it’s not real likely to cause a problem. So there’s a little margin here.
And heat costs money, and bake cycles are short. So there’s just not much reason to bake em harder than you have to. But the truth is a lot of powdercoaters barely know what they’re doing, or learn it just through doing it and treat it as a bit of an art. Sometimes they might smash the oven up higher in order to “go faster”, sometimes of course the oven might not be working right or might have hot and cold spots. And they may preheat before the powder to degas or burn off contaminants. And yep there are some places that offer “high temperature powder” as a selling point for wheels, trading off concern about brake heat. Which IMO is mostly bollocks but more importantly could need more bake heat.
So it definitely gets wobbly in the real world. I have a place I trust, but before I knew much about this I used a place that in hindsight I wouldn’t trust to bake a supermarket pizza. Honestly if you ask the question “I’m a wee bit concerned about heat, how hot do you bake the wheels and for how long” you’re almost just listening for how clear and immediate the answer is as much as what it is, if the guy is wobbly or vague I would worry because this is stuff they should not just know but have burned into their brains.
(just occasionally yoy hear of a place that treats it like a trade secret, either because they genuinely think they have a magic number or just to try and present a high end process impression, that’s not so easy)
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I once ran a factory with electric annealing ovens. We were BS5750 and also CAA approved. The BS5750 assessor only wanted to know the calibration status of the temperature controller. The CAA assessor wanted a temperature map of the oven. I wonder how many powder coaters really know what is happening inside their ovens.
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Yeah, exactly. Even with the best intentions there’s tons of room for problems to creep in. Though at the same time you’d have to be quite a long way out for it to be a problem, there’s good margins. But if the operator decides to bake at the top end, AND the oven’s got issues, then it’s definitely possible to burn through those margins.