I thought they were the front ^^^^

Baz,

to reflect the comments on here already, you need to get these off the car ASAP.

You can check for cracks using eddy current or x-ray, but looking at the failure, it's more likely a material defect than a single damage event, and hence likely to fail on the other wheels as well.

Don't send both wheels to Fiat, retain a damaged one incase you need a second opinion.

If fiat aren't interested, if you can get then to Stevenage I'd be willing to have a quick look for a couple of hours. I do forensic engineering for a aerospace company so I look at fatigue failures all the time.

Oops. You're right front wheels it is.

*note to oneself* Must take up reading lessons again.

I think he said it was both front wheels dude.

Ross

Yeah it was both front wheels. They`ve been on the front ever since I got the car,so the back ones won`t have been subjected to the same stresses that the front have experienced.

The thing that scares me most is I can remember seeing a chalky mark on the back of one of the wheels way back when I fitted my LE caps not long after getting it which I put down to being just muck .

I balanced the wheels myself when I fitted the tyres at the same time and there was nothing unusual like excessive buckling so it`s taken around a year to get into that kind of state and the only vibrations i`ve had were 5 mins before total failure.

I must admit i`ve never actively looked for cracks as I never had any cause to do so,but that`s changed now .

Baz

Is this something the Mods/Emjay should now be looking at? Insanitysauce has offered to look at these but obviously Baz does not want to carry the costs for delivery to Stevenage...could this come from club funds? Without aid this may never be investigated.
It sounds like at the very least there should be post to investigate the temps used when having your rims refurbished, assuming the person doing this work knows not to turn their oven up to 200c/400f is potentially very dangerous (of course I am assuming this how the fault occurred)

and before you ask yes i will be joing the Fiat Coupe Club proper in April.

Nigel has already said he's going to contact Fiat so I suggest we see what comes out of that. And knowing Nigel, I'm sure he'll manage to persuade them to cover any postage costs, if dropping it in to the local dealership isn't an option.

Ok Matt, new on here and don't know charters on the forum yet. Had to ask though.
Cheers

I'm currently working on getting a contact name & number at Fiat UK HQ in Slough - the normal Fiat customer support number puts you through to Bombay or something - fine for sorting out stuff like "where can I get my Punto serviced?" but I reckon there would be a language barrier when it comes to "are there any instances of heat-induced metal fatigue on Coupe wheels?"

Last time I called them, the person I spoke to denied that Fiat had ever made a car called a Coupe

OK - managed to un-earth a number at Fiat HQ - discussed the problem with them - they seemed genuinely concerned, as its a safety-related item.

I'm currently on hold with Fiat's international call centre, who (when they stop asking me for a reg number) will log an incident and return it to Fiat HQ

chances are that the wheel will have to be taken

I'll keep you posted

ROFL!

Good to hear Nigel.

Ross

Lmao,


Good work Nigel

OK - Incident has been logged and I'm waiting for Fiat UK to call me back

I will have to come clean from the outset that these wheels have been refurbed and that it may be the heat that has initiated the failure.

However, the stance I will take is that wheels shouldn't fail due to the relatively modest heat required for paintowrk or powder coating. In any event, Fiat may choose to make a statement that Coupe owners wishing to refurb wheels should do so with a low-bake process, or preferably, no heat at all

I reckon the next stage will be to let Fiat see the wheel. However, at this stage, I'm REALLY reluctant to let it out of Baz's sight.

Baz - how close is your nearest Fiat dealer and have you managed to source some more wheels so that you can carry on driving?

Ah - almost forgot - happy birthday Baz

Baz you can borrow 2 of mines for a short time if ya like?

Ross

should this be reported to VOSA as well as fiat ?

Well I suppose the nearest dealer to me would be in Ayr which would be no probs to drop into .

I assume nobody else has found any cracks (MattB told his spare set were fine anyway ) when there has been no other posts,so that can only be a good thing .

Baz

Might be on a sticky wicket with that one. It really depends on the original alloy grade and subsequent heat treatment.

The annealing temperature for Al is roughly 2 hours at min 340°C, but it depends on the aging temperature. For 6082 T6 its roughly 180°C for 7 hours, but if i were recommending a process to a design engineer, I wouldn't be comfortable using any process above 200°C for a significant length of time, due to the risk of overaging or losing the T6. This can result in a drop of 60% in the RT strength - worst case.

I recommend aluminium processes all the time but for aerospace, and so the safety factors may be larger, but I would not let a design engineer use a process on a 6082 T6 above 200°C without providing me with a test piece - unless it was for a short time.

IIRC some powder coats processes can require much as between 200 to 235°C.

Hence, who did the powder coating as they should know that some grades of Al can be problematic.

I'm with InsanitySauce on this one, if they have been powder coated, Fiat wont give a monkeys.

I work within the warranty department of a large Tier 1 supplier, so I kind of know what goes on at dealers/manufacturing/headquarters within the automotive sector (Not Fiat btw). I'd be massivly suprised if Fiat even entertain looking into them. The wheels would need to go back to Speedline, who will see they have been tampered with, and they'll just reject the claim.

Ben

PS Christ you were lucky! Could have been a lot worse.

I wouldnt expect fiat to take responsability on a case like this where the wheels have had an aftermarket job done to them. But I would expect it to be known to others that if the cracks are due to this coating of paint by some sort of heat treatment. That it may result in a failer of this kind.

Still be worth pursuing with fiat though.

Nigel can you see if you can found out the alloy and heat treatment? This might be difficult as most automotive guys use performance specs rather than materials specs.

I am surprised by the failure if it is due to a post manufacture process, but due to the fact its a wheel, I think high cycle fatigue may be the issue, which occurs at stresses significantly below the ultimate strength.

Baz, if get time could you take a really clear picture of the failure surface, so I can see the texture - I might be able to see the cause. Just put a decent digital camera on macro mode.

I`ll get some more detailed photos of the broken surfaces tomorrow. Like I said above though nobody else has been on to say they`ve noticed cracks so it`s probably just lucky me and FIAT probably won`t be too bothered especially when they`re non-standard coating.

I`m still trying to get in contact with the previous owner to find out where he got the wheels done,but have had no reply yet .

Baz

Will these pics be of any use . Not the best pics but they`re not in the easiest of positions to get close into.

Surface 01

Surface 02

Surface 03

Baz

Good quality pics there baz.

I notice that they all seem to as if peel away from each other. As if they were not sticking togeather properly?

Thanks Baz

Without a good look its difficult to say, and they would need to be cleaned up properly.
This is pretty much as you would expect and most things have already been suggested but to bring together.

based on your pictures surface 3 looks like its the one that failed first, probably increasing the load on the other two.

The crack in image 1 has progressed approximately 60% of the thickness before final failure and is showing high cycle, low cycle and ductile failure modes.

Image 2 is a bit confusing as there may be some corrosion, but it appears to have less fatigue and more ductile failure modes than image1 and so I think was the last to go. That said it looks as though a crack has gone complete through the section at the thin end.

All cracks appear to originate at the same place, where the cross section is thinest on the inside edge. The surface looks as though its showing crazing due to stretching, but it could be the lacquer.

Most fatigue is surface initiated, so have a feel for any rough areas on the inside edge.

Obviously, I've not seen these in the flesh, but I would suggest one of the following is the most probable cause.

1. Overheating during powder coating or localised repair has removed the correct temper condition - this can be checked by microhardness/ hardness. I would be surprised if this was the sole cause as a wheel is safety critical and there must be reasonable safety factors in the materials selection.

2. Powder coating has modified the surface due to improper processing leaving a rough area or crazing in a notch sensitive area in the design. - you may be able to feel a rough area on the rear side where the processor didn't do a good job, or the crazing initiated it. Could be combined with 1.
Al alloys are very sensitive to surface effects, and i would always recommend shot blasting after anodising for example to increase fatigue resistance.

3. Material defect - looking at the images I doubt it, but easy to check.

Cheers mate,I`ll maybe give the wheel a clean up and take some more photos. Whereabouts are you from because I`ll probably bring the wheel with me to the Big Coop Meet (if i`ve still got it anyway) if you want to have a closer inspection .

Baz

don't - leave it exactly as it is - if it gets tested, then the testers can clean it up.

By cleaning it, you may destroy evidence or at least make it more difficult to unearth

Agreed don't do any more until fiat have seen it, let the experts clean it up. All those dirty particles can be collected analysed and may lead to the solution.

The most common thing people do is try to fit the broken parts back together again, which damages and smears the failure surface making finding the cause almost impossible.

No probs,I`ll leave it as it is .

Baz

When you say overheating, would it be possible for a binding brake to create that amount of heat in the wheel ?

Im just trying to think of how a wheel could be exposed to enough heating/cooling cycles to allow the metal to fail ?

That part of the wheel is directly oposite the disc ?