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I was driving the other day - car (1998 Toyota RAV4, FWD) recently serviced, four brand new tires recently fitted - when I heard a loud bang from my front left wheel. I eased to a halt, thinking one of the new tires might have burst: everything looked fine, but one of the five lug nuts for that wheel was missing (the bolt was still there, looking dirty but otherwise fine).

What could have happened and how can I prevent it? I'm guessing something to do with metal fatigue? Makes me a little nervous about my other, normal-looking but probably rather elderly and abused lug nuts.

The tires were fitted by a mechanic at the same time as doing other servicing. I didn't check how tight the lugs were before driving (probably should have) but I checked the others after this happened, and they seemed fine.

When this happened, I was driving at a moderate speed (50mph?) along a smooth, straight road, and had been driving for maybe 3 hours on a hot but not unusually hot West African morning (maybe 32°C when this happened? Probably 24°C when I set out).

The only unusual thing I can think of is I'd underestimated a few pot holes earlier in the journey and hit them faster than I should (25mph-ish), shaking the car but causing no visible damage.

It's worth mentioning that some of the parts sold in car stores here probably wouldn't meet regulatory standards in places like Europe, so poor quality lugs is a possibility (though I have no idea how to check such a thing).


The lug nuts looked a little like these:

enter image description here

Image from eBay, note there's no reason to think these are the same brand, they just look similar.

And in the missing one, there was nothing left at all, just a bare bolt poking out with nothing on its screw thread. I can't find a suitable image and don't fancy removing a lug just to take one - imagine a bare bolt similar in length to these lugs sticking out from a hole in the wheel where the nut should be.

If it was the end sheering off, that'd be easier to understand, but the whole nut disappeared from the bolt.

  • Are these nuts, or bolts? It sounds like you are describing a bolt that the head has snapped off. Is that correct? – HandyHowie Feb 25 '16 at 13:01
  • @HandyHowie see latest edit – user568458 Feb 25 '16 at 13:10
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As long as the rest are tight (and torqued to spec), I would put a new nut on and torque it to spec. Given that there isn't and left over metal on the stud, like the nut stripped out, I would say it wasn't torqued to spec and worked itself loose. The bang you heard might had been the wheel flinging the nut.

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    So the bang might have been the fast-flying lug hitting the wheel arch or similar? – user568458 Feb 25 '16 at 13:23
  • its possible yes. You can look around the area for any other damage. – rpmerf Feb 25 '16 at 13:36
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    @user568458 If the stud isn't broken and the nut came off take it back to the place it was serviced and demand a new lug nut. That's BS and if the other nuts had been loose could of been life threatening. – Ben Feb 25 '16 at 22:25
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    "Torqued to spec" is the correct approach and is different from "they seemed fine". Use a torque wrench to ensure they're neither too loose nor too tight. This should be re-checked, per my Haynes guide, after 25 miles. It's possible the nut worked itself loose through normal use, for various reasons ("paint, debris, corrosion, or a tight and binding centering hole over the wheel hub"); some of these aren't the garage's fault. Retorquing would have caught it. – Mathieu K. May 13 '16 at 14:18
  • Is it also possible there was a defect in the structure of the metal and the nut split? OP mentioned possible quality issues. If it split rather than stripped, would it leave any traces? – Mathieu K. May 13 '16 at 14:21

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