My grandson drives a Mercedes 2001 van; the front passenger wheel fell off while driving, but the wheel nuts remained in place, and did not come off. The holes on the wheel had been enlarged enough for the wheel to fall off. What could cause this to happen?
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Pls include a photo of the wheel holes if at all possible, thanks. – Fattie Apr 26 '23 at 10:44
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It seems to be an extreme case, but if the lug nuts were not fully secured against the rim, the forces involved in driving can erode the holes in the wheel, especially if the wheel is not steel and is a softer alloy of metals.
In a static position, the wheel stud is resting in the portion of the hole in the wheel farthest from the center. If the nut is not tight, there will be space above the wheel stud. If the nut is partially tightened, it will keep the wheel against the hub but will not keep the wheel from moving around the stud.
As the vehicle travels, each succeeding wheel stud moves as far away from the center of the wheel as possible, simultaneously as a diametrically opposite wheel stud is moved closer to the center of the wheel. This rotation causes the space also to "relocate." The space does not really move, it's the wheel that moves, wearing against the wheel nut, wearing the smallest amount.
At normal travel speeds, this is thousands of times per trip. Eventually the wear becomes so great that the movement is increased, along with the acceleration of wear. A "sensitive" driver would have noticed changes in handling, especially while cornering. It should have been detected earlier as you've noted it was a front wheel and should have been felt as a vague feeling in the steering wheel.
This image above, from carid.com represents a common profile for a wheel lug nut. The taper must be a matching type, presented in this image below from drivenproducts.com:
Overlooked in my answer is the possibility that there is a mismatch between the lug nut facing and the wheel facing types.
fred_dot_u
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Never mind feeling it. The driver should have heard it clunking. I've had a wheel work loose while driving. You hear the wheel banging on the lug nuts. – JRE Apr 25 '23 at 13:02
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2If the operator is enjoying a period-appropriate melody for his (possibly young) age, one might think hearing anything else is excluded. – fred_dot_u Apr 25 '23 at 13:07
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2I've been in a vehicle which had loose lug nuts and you wouldn't hear them doing anything unless the vehicle was turning. Then it sounded like a bad CVJ. – Pᴀᴜʟsᴛᴇʀ2 Apr 25 '23 at 15:30
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The concept that the five holes were *all enlarged enough through wear* that the lug nuts fell through ... seems incredible to me ?!?!? – Fattie Apr 25 '23 at 19:11
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"if the lug nuts were not fully secured" means torqued to factory specification, not just hand tightened. – chili555 Apr 26 '23 at 01:05
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@Fattie possible if the wear was severe enough. More likely that the nuts just got pushed off though after they became loose enough. I'd be surprised if the lug nuts are still attached to the vehicle. – Christopher Hunter Apr 26 '23 at 04:42
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1right, but per the OP "the wheel nuts remained in place, and did not come off. The holes on the wheel had been enlarged enough for the wheel to fall off". This seems incredibly unlikely, really it seems impossible. We talking about the bolts wearing away the actual wheel, and doing so in such a consistent manner that all five holes in the wheel literally become about three times their usual diameter. (Indeed, all the while not actually simply wearing away / snapping the bolts! It seems impossible. – Fattie Apr 26 '23 at 10:27
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1Regarding an incorrect seat shape. It's a good point, but don't forget nothing's turning, it would just be stuck there at a frictiony point. General vibration could cause some wear or scratches underneath, but the idea that the seat could totally wear through about 1/2 inch of some sort of metal, and then enlarge it a bit more so that the nuts go right through, seems incredible. – Fattie Apr 26 '23 at 10:33
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1@Fattie It's hilarious how everyone's contorting themselves into bizarre "what-if" scenarios, trying to explain away something so unlikely. The reality is almost certain to be grandson did something stupid and doesn't want grandpa to know - we were all young once. – SnakeDoc Apr 26 '23 at 18:09
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Yes, they were simply loose, and the rotational force eroded the lug holes in the wheel. @Fattie And yet, I've seen it more than once, this story not included. – Oct 26 '23 at 22:53
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@Pᴀᴜʟsᴛᴇʀ2 Yep. If you're paying attention to everything the vehicle is doing, you'll feel and hear a soft rumble that quickly become big a alarming, and then the wheel flys of less than 15 seconds later. It goes from hanging on to flying down the road without you just like that. – Oct 26 '23 at 22:56
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"wallowed"
Amazingly to me, it does seem to be a thing that, if you drive with the lugnuts not correctly tight, the holes can be deformed / enlarged / oval-ized a bit.
The usual mechanic's word for this seems to be "wallowed" (various spellings).
If you type exactly this in to google:
"car wheel bolt holes wallowed"
you may find some information.
To me it seems incredible that the holes would wallow-out so much that they would, all five, be uniformly bigger diameter than the actual nuts, and all of this without destroying the studs or the vehicle being totally inoperable anyway.
I'd say any copper would suspect some sort of crime or bizarre prank or such.
(Random example. A tire store totally forgot to put on the lugnuts, the wheel fell off, and then when the tire store guys ran over to see what happened, someone quickly screwed the nuts on to the now-demolished car whilst yelling "wow the wheel popped over the lugnuts!" or such.)
Anyway "wallowed" seems to be yoru search term for more information.
Fattie
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Well Thank You so much for all this info, I feel confident your answer is correct. – juliann Apr 27 '23 at 00:15