What's caused this potentially dangerous failure?

[16plates]

A friend had this fail on his way to work at 70mph this morning...



I've never seen anything like it and can't even suggest how that's happened?? No impact, just failed.

[nipsips]

Looks rusty :/

Is it the spare?

[Megaflow]

I'm assuming that is a steel wheel? Bit hard without something to scale it with.

If so, I'm going to suggest it was slid sideways into a kerb at some point.

[GTIR]

Id say it's had an impact in the past and afterwards put in as a spare and the rust has caused fatigue. Looks like a fracture top left.

Is it from an older car?

[Rickyy]

Combination of corrosion, heat from a sticking brake and an unbalanced wheel?

Hope no one was hurt!

[Matt UK]

nipsips said:

Looks rusty :/

Is it the spare?

Agreed, if it's spent 10+ years exposed to the elements / damp.

[cambiker71]

Looks like over tightened wheel nuts, you can see the recently broken sections because they're shiny metal but the break is rusty near the wheel nut holes. I'd guess it's been like this for some time and only recently the cracks have spread away from the over tightened broken parts.

[vanordinaire]

It looks like it's been cracked for a while and gradually getting worse, notice the rust on the broken edges next to the nuts, only a small bit is a fresh break. Maybe it hasn't been balanced properly and it's had a wobble which has gradually shaken it apart.

[Steffan]

Looks very clean to me around the edge with some older corrosion. Something odd as suggested then allowed to rust. But I have never seen a wheel break this cleanly without distortion on the rest indicating a collision a some time. Very odd indeed.

[16plates]

nipsips said:

Looks rusty :/

Is it the spare?

No it's the front O/S wheel, spare was put on to get him moving again.

It's a 12 year old Ford KA.

[bbc]

Probably asking the obvious, but has he checked the other wheels?

[robinessex]

Classic fatigue failure.

[Matt UK]

16plates said:

No it's the front O/S wheel, spare was put on to get him moving again.

It's a 12 year old Ford KA.

Ah, well they do rust like a bugger everywhere else, so no reason why the wheels wouldn't dissolve also...

[sars]

Looks like stress induced cracking, wheel not fitted correctly causing it to wiggle (very technical term) and as the centre of the wheel is fixed to the hub, movement occurs adjacent to it and thus is where it fatigues and fails

[cptsideways]

I have had two trailer wheels do exactly this. Partly overloading them didn't help nor did the fact they were Chinese tat.

Is that an original Ford wheel?

[zed4]

Rust? You guys should see some of the (boat) trailer wheels some of my customers bring intro me at work! Unbelievable! I'm amazed that's just broken, it certainly doesn't look that badly corroded. Must have been impacted at some point and fatigued.

[996TT02]

robinessex said:

Classic fatigue failure.

This.

But odd, never saw this happen, steel is very tough and resistant.

[cptsideways]

cptsideways said:

I have had two trailer wheels do exactly this. Partly overloading them didn't help nor did the fact they were Chinese tat.

My failures were both boat trailer wheels!

[robinessex]

The bolt holes are designed like this. Reinforces the hole, and allows a better bolt contact. AS LONG AS YOU USE THE CORRECT MATCHING BOLTS.

[CrutyRammers]

The Crack Fox said:

I disagree. The threads would strip before it damaged the steel structurally. The fault line runs radially, around the rim, and the signs of rust make me think this has been whacked up a kerb at some time and perhaps somehow bashed back into shape. I'd like to see the other side to be sure.

That's what I thought. Can't imagine that overtightening would cause that. A very odd failure though.