I’m looking for technical help or recommendations on: __
Just had a catastrophic failure of front near side alloy where the rim flew off complete with tyre on a bend at about 40-50 mph ….
The 17 inch original alloy just appeared to shatter and come apart ?
The car following reported to me a ticking noise heard in line with revolutions at 15-20 mph before wiped out by wind noise ? I could hear a ticking when close to hedges etc reflected back but thought just like a stone on tyre ?
He was about 3-4 car lengths behind me
No potholes on route or damage to wheel / tyre visible or history of any damage ?
Carried a space saver tyre which saved the day as foam tyre repair would have been useless ! And managed to get car lifted from ground zero to get it on !
Still in shock but very lucky escape !
Internet search of issue revealed this can occur after powder coating alloy wheels as makes them brittle and a ticking noise is a prelude to failure ?
I had mine done 2 years ago to tidy them up and have done 2000+ miles since and no cracks etc visible on cleaning etc
Yours is the second failure of powdercoated wheels I have seen reported recently (unless you have also shared this on other forums, can’t remember where specifically at the moment) and if so suggests warnings about aftermarket treatment should be taken seriously.
A NC factory wheel recently failed in the same manner on a track day. Owner is uncertain if the wheel had been previously powdercoated or had prior damage.
Yes, powdercoating, if the temperature is too high, will weaken the alloy. Every wheel restorer will claim to be an expert. People tend to gravitate to who ever gives the best (cheapest) deal.
I had a set of rare factory Panasports restored some years back. The restorer point blank refused to use powdercoat, for those reasons. A mistake can make the wheels scrap, but you don’t know until they fall apart.
Powder coat is also basically a plastic coating. I wonder if its laid on a bit thick, cracking can be masked.
But also, Mazda (Enkei) wheels have been known to just crack.
I knew nothing about the issue/ risk with powder coating and it was a reputable local company who did it but given time since and mileage covered they are likely to say it might be ‘pothole ‘ damage as we have a lot around here ….just back from mx5 tour of Portugal/ Spain bendy heaven so count myself lucky it did not happen over there !
This is the only forum I have posted on
I’m not a metallurgist however I know a thing or two about materials. Personally I think its plausible that powered coating has affected the wheel structure but not in the way you think, these sort of temperatures you are likely achieve during heavy braking - like on a track day.
I’m taking a known aluminium grade (used in conventional casting) AlSi10Mg as example to provide some numbers.
Aluminium alloy AlSi10Mg melting point is at 570 °C
Aluminium AlSi10Mg alloy normally subjected to a T6 heat treatment in which a solution treatment is carried out at around 530°C followed by ageing at temperatures in the range 150–180°C (reference) for anything between 5 to 24h (reference)
powders bake at around 175-205 °C, for about 10 to 15 minutes
So it may seem that powder coating has similar temperatures to metal aging… But what is aging, one may ask? Basically all metals have micro fractures, aging block these dislocations in the metal, increasing the strength and hardness of a metal alloy while reducing its ductility. Ductility is the ability of a material to deform plastically without fracturing - and that’s quite important. reference
I’m pretty sure that if I go on a track day my wheels and brakes will get close to 150–180°C
I don’t think powder coating will significantly change your wheels structure behaviour. It will have an effect but the same sort of effect will have by tracking your car.
The wheel that broke on track - well… how many heat cycles did it have? It probably has become too stiff and broke under loading.
The car in this tread? - not sure about that one… I’m thinking damaged or repaired wheel ?
Spooky that two wheel failures have happened in such short time period (and they are the same type/shape of wheels)
How strange! The other car is mine and happened at about 90mph as I turned in. Bit more dramatic especially as the wheel ended up in the sea
I bought them from someone a few months ago, did 2 track days on them without any issues but both days were on PS4 in the damp so not huge force going through them.
Anglesey was the first day I ran AR1 (very grippy tyres) and was able to drive the car on track in the dry.
The recovery guy mentioned it looked like the inside of the metal was different shades (light and dark grey) which to him indicated corrosion. But others mentioned powdercoating could have weakened it.
Mine failed at 11:30am. After 3 sessions on track. I was driving it hard-ish but nowhere near the limit of the tyres as I have run the same tyres on my M3 which weighed the same as the MX5 but had twice the power.
I was leading three cars on a local bendy route had stopped for 20 minutes earlier for a water break so would have cooled off ? Don’t use brakes much tbh and as I know the road I was quick but engine braking was used and carried speed under drive … Sticky Uniroyals stuck like glue but it would have put a lot of cornering forces into wheel rather like a track day force
If powdercoat cannot get hot enough (I have heard contrary opinions), then why is it powder coated wheels are the ones lying in bits.
Wheels crack, and the cracks are visible. Is powdercoating masking old damage.
This does the rounds:
Alan Peltier HRE Performance Wheels
With the greatest respect, this is an engineering question. It is not for refinishers or chrome platers to decide. Many forged wheels have been weight optimized for a specific load on a specific vehicle. That is, the weight is reduced to the absolute minimum required by the vehicle load, otherwise why bother? Therefore, any loss of strength compromises the reliability of the part and its load carrying capability as well. And potentially, the safety of the driver. The chroming process reduces the ductility and strength of the forged alloy to varying degrees, depending upon the methods used and the specific plating alloy used. This phenomenon, known as hydrogen embrittlement, is well documented scientifically and carefully tested for in aircraft/aerospace components.Wheels can certainly be designed with chroming in mind. Excess material and mass can be added during manufacturing to compensate for losses in the chroming tank. This thread, however, deals with REFINISHING. It is our opinion that there are simply too many unknowns in these processes to risk weakening the alloy. Therefore, for forged, heat treated alloys, we do not recommend powder coating except by trained expert facilities with quality systems and Brinell hardness testing systems. And we do not recommend chroming forged wheels, unless the wheel was designed for this finish. A cure temp of 375 degrees Fahrenheit for 30 minutes will overage the alloy and begin the annealing process. This is not recommended by us, HRE, OZ, Champion Motorsports (who forbids powder coat entirely), BBS and most other forged wheel companies. This also includes the 50 or so forged wheel companies worldwide for which we supply the blank forgings.Many of these companies will void the warranty for any refinish not done under their control. We don’t blame them. As far as the OEs are concerned, if you refinish or plate a factory wheel and ANYTHING goes wrong, you are on your own: ZERO warranty. Safety and liability are the issues. We don’t know anything about your company, its processes, quality systems or technology. But if a wheel is refinished and then fails in service, or someone gets hurt, we all know who gets served with a lawsuit. The USA has 4% of the world’s population and over 50% of the world’s lawyers.
exact same thing has recently happened to a bloke on a track day at Anglesey. Thought was you for a minute! Same car/colour/wheels the lot.
Wheels just get old and eventually will crack, bend, etc. Powder coating won’t add strength to them, it’ll only speed up the wear. Not to say it’s bad, but it’s an extra process your wheel will go through.
I had some cracks appear on my Enkei (Civic Type R) after powder coating, but they were old battered wheels. Same on an old E36 coupe.
As with any other part, they wear. I wouldn’t buy old 2nd hand wheels for this reason.
I agree that that powder coating is within the aging heating process temperature range. But I’m also saying that by tracking your car the wheels will also see these temperatures.
Aging making the wheels stiffer and less ductile - thus they will break easier under fatigue loads. I don’t think these wheel’s failure was caused by exceeding design loads (under braking or bump). In both cases this was a fatigue failure and I would personally give a little bit of gravity to the fact they are the same type/shape/age wheels.
as for this …
you will have some material added during electroplating but its marginal and IMHO comparable to painting or powered coating. In addition electroplating will affect corrosion resistance and surface tension properties but not really change the internal characteristics of the alloy.
This ageing aspect of various aluminium alloys rings a big loud bell from our family history.
My grandfather owned a very lively 30/98 Vauxhall with custom-built Dural body. However as soon as my uncle was old enough to learn to drive, the 30/98 was promptly sold, with the excuse being “The body will soon be crystallising into a much larger number of smaller pieces. I’m selling it while I still can!”
Those words of his were repeated many times by my mother who had fond memories of the superb car being explored to the maximum by her dad, and she also wanted to drive it. Apparently, in those days (1920s, 1930s) it was generally accepted that the useful life for sheet Dural was about fifteen years.
I assume the various commercial alloys of aluminium have improved immensely since then, but I’m not surprised to see wheels failing. The husband of one of SWMBO’s friends was a Police driver when they used the fast Capris, and he wrote off numerous sets of alloys, sometimes within days, until they gave up on them and fitted steel wheels instead.
I was quoting Alan Peltier of HRE. The controversy over powdercoating wheels has existed for 20+ years. A forum discussion is not going to put it to rest.
I have never done a trackday where I have been driving continuously for 3-4 hours of hard braking. Usually only 15-20 minutes tops, with decent straight stretches.
This design of wheel has been around for over a decades, with billions of accrued miles in use, including environments far more severe that the UK (US, Canada, Australia). Suggest you research other MX5 user sites, before suggesting there is an engineering design issue with an obsolete Mazda design.
You know, these days I spend a lot of time in Thailand. The number of cars over there on knock-off TE37s is beyond a joke, on some really atrocious roads (but there are also really really nice roads there). But they are generally not lying in a ditch with the rims around their neck.
I don’t think its the design of the wheels per se. Those little markings on the wheels, such as JWL, denote some pretty stiff testing.
Perhaps there is an unreasonable expectation of the working life of a car. 20 years ago, a 10 year old car was an old car. Now we have numerous threads expressing surprise, shock, anger, that a 17 year old car has a bit of rust on it. Certain suppliers will think nothing of selling 30 year old wheels for £1000 because they are “rare”. A preponderance of wheel restorers will kid you that a precision part of the suspension can give service ad infinitum with a lick of paint/paint substitute.
you definitely won that trackday mate and took a trophy home 
