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:
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.