I had used these spacers many times in the past and today was no different. I swapped back from my treadless stockies to my fwd offset rims, put the 10mm spacers on again. Did the nuts up bloody tight and drove off to get some parts, 10mins up the main road i was on, i shat myself.
With no warning the rear right of the car suddenly dropped and started scraping, i looked up to see my wheel fly past me. Instantly i jumped on the brakes, nothing, straight to the floor. I then yanked handbrake all the way up, nothing. As i was heading towards a red light doing 60kph i just dropped it in 1st and killed the engine. i pulled up 50m from the intersection.
In disbelief i got out to see my wheel flying down the footpath, it took out a shop sign like it was made of paper and had everyone at the bus stop jumping out the way as it cruised towards them. Luckily no one was hurt.
If that dosnt get the adrenalin going i dont no what will, scary stuff. I looked down the road to see a big long scratch in the road, my drum was sitting in the gutter, a bit further up and within 10m of themselves were all 4 wheelnuts, undamaged and half of my wheel spacer, the rest was gone.
As i was blocking one lane in peak hour traffic i quickly jacked it up to see my wheel cyl had popped out and the handbrake wasnt working because there was no drum. The drum wouldnt fit back on so i threw my spare on without it, adjusted the handbrake all the way and slowly drove round the corner into a carpark were i popped the wheel cyl back in, chucked the drum back and got bake fliud. I could only bleed the front right as i was by myself but this just.... gave me enough brakes to crawl home.
At home i assesed the damage, my poor rear gaurd is mashed, the back is all folded under, haha as a bonus its flared my gaurd nicelly. I managed to get it mechanically all fixed up but damn that was a hard lesson to learn, seems im learning the hard way a fair bit latelly better slow down a bit!
And no there were no warning sounds/vibrations, so there you go, there dodgy and illegal for a reason, im only going to use the proper countersunk allen key version from now if i absolutelly have to. I will post a pic of gaurd when i get a chance.

and thats why i made my r31 diff wider when i cut it down

not saying its a good idea to use spacers, but im sure something made out of steel or even an alloy one that was closed in (no big weight saving holes) would be 1000 times better than these

I dont get it? how did the wheel nuts all come off? I thought you were going to say the studs had failed, but if you were able to put it all together again they must be OK. How do four wheel nuts all come off at once?

Hmmm, I can only think of one reason, and not necessarily because it broke the spacer.

I'm inclined to suspect that the wheel spacer was a victim of the problem, rather than the cause.

If the spacer was properly fitted & the wheel nuts done up securely, then it will all stay together, but wheel nuts that are not secure, ... well that's a different story.
This is by far the most common cause of wheel sheding.

The only other thing would be if the spacer broke up & pieces fell out allowing the wheel nuts to be damn loose, which seems unlikely.
I suggest that you see if you can find the missing pieces of the spacer & note their location. If it's a bit of a way back before the location of the nuts, then this would be the cause, but if at the same location, or after the wheel came off, then unsecured nuts would be the main suspect.

It seems that even if the spacer broke in half... the lug nuts aren't going to shear, it seems like the lugnuts failed, then the wheel came off and the spacer finally went flying...

it would be really hard to break one of those spacers in a proper install, seems much more likely the failure was something mundane like loose lugnuts...

Crikey, I'm glad to hear you are OK and that no one was hurt.

Wheel spacers are not illegal in the USA, and I have heard of no accidents from them.

The most common reason for wheels to come off from what I understand is overtightening of the lugnuts. There is a very low torque specification on 1200 lugnuts. This will happen suddenly and with or without use of spacer. But it is still rare.

Lugnuts too loose can back off -- but they should give a warning of vibrations etc for a while before it happens?

what road were you on ?

hey... if the lug nuts were sitting there undamaged... meaning they didn't shear the studs, then there was something strange going on, all 4 lugnuts generally don't fall off, were the right ones used? what condition are the lug studs in? did you have 9+ threads engaged on the studs? something funny going on here...
when were they last torqued?

tis a bit weird isnt it, as even if the spacer broke off and departed the vehicle, the wheel nuts would sorta come off slowly and the wheel would vibrate like a bitch

and you wouldnt think that all the wheel nuts would be together