So, this happened the other day

[Joe 5]

Apparently it was well over tightened and caused the head to pop off. It took Toyota a while to get it off! 

This is the second issue I've had with garages gunning wheel nuts on. The fist time (different garage) they didn't tread it properly and chewed the whole stud up. Has anyone else experienced this?

[Church 209]

Weird to hear overtightening from officials. Official dealerships often don't want to step outside anything stock, and keep at official manufacturer procedures & torque values, exactly to not see any legal action or something breaking/to warranty and such.

To not need overtightening main thing to remember is to clean stud threads before putting nut back, less of usage of misc. anti-seize greases (which btw changes torque nuts need to be tightened AFAIK).

 

[Varelco 211]

It's no unheard of. Wheel nuts often get blasted tight with an impact gun, way tighter than they need to be and I'm sure the shock motion from the gun doesn't help

[Church 209]

But stock lugnuts are steel, should much better withstand impact tools usage, at least their threads from stripping when impact used on. It's usually aftermarket aluminum ones that are advised to tighten/untighten using hand tools and tools only for quick light tightening/removal. And imho stock lugnuts if they are of closed end and used on stock wheels, should enough clearance to cap to never shear off even if overtightened.

By chance, are your wheels aftermarket (and maybe with deaper lugnut seat bores)?

I'd take extra attention to wherever nots were bolted on. Be it just dealership, or eg. tire shop. If one overtightens till some part breaks, something is off. Be it sloppy overzealous tech air impact trigger-happiness, or different length lugnuts needed, if specific aftermarket wheels need such. With overtightening i may expect that they can strip stud threads aswell at some point.

[Joe 5]

27 minutes ago, Church said:

Weird to hear overtightening from officials. Official dealerships often don't want to step outside anything stock, and keep at official manufacturer procedures & torque values, exactly to not see any legal action or something breaking/to warranty and such.

To not need overtightening main thing to remember is to clean stud threads before putting nut back, less of usage of misc. anti-seize greases (which btw changes torque nuts need to be tightened AFAIK).

 

Sorry Church, I should clarify. These were tyre garages and not official Toyota dealerships.. 

[Joe 5]

4 minutes ago, Church said:

But stock lugnuts are steel, should much better withstand impact tools usage, at least their threads from stripping when impact used on. It's usually aftermarket aluminum ones that are advised to tighten/untighten using hand tools and tools only for quick light tightening/removal. And imho stock lugnuts if they are of closed end and used on stock wheels, should enough clearance to cap to never shear off even if overtightened.

By chance, are your wheels aftermarket (and maybe with deaper lugnut seat bores)?

I'd take extra attention to wherever nots were bolted on. Be it just dealership, or eg. tire shop. If one overtightens till some part breaks, something is off. Be it sloppy overzealous tech air impact trigger-happiness, or different length lugnuts needed, if specific aftermarket wheels need such. With overtightening i may expect that they can strip stud threads aswell at some point.

Everything on my car is stock and oem. The only time I've not used Toyota has been for new tyres which is where I've had issues. 

The car did have a previous owner but I checked stud lengths were correct when the first one was stripped and had to get a new one.

[Varelco 211]

Cant figure out why the dome part broke off as that is not really in contact with anything (nut gun or wheel) The broken one is corroded which might have something to do with it.

[Joe 5]

1 hour ago, Varelco said:

Cant figure out why the dome part broke off as that is not really in contact with anything (nut gun or wheel) The broken one is corroded which might have something to do with it.

It's corroded since breaking. It was clean when it first happened I just hadn't got round to taking a pic of it and posting. 

When I first looked at it, the top of the nut without the cap was pretty flush with the stud and there was no way I could remove it with hand tools. I suspect that some grit or water/oil got in between the stud and the cap when the tyres were changed. Coupled with the over tightening is what made it pop.

[Church 209]

If one cannot remove it with hand tools, it was too tight. There is specific torque value lugnuts needs to be tightened, and that torque is well within what hand tools should be capable of. Our cars in boot have stock lugnut wrench (for changing to spare emergencies), which should provide very aproximated somewhat right torque, due which it is of specific length(lever length). At least if one uses tube over that wrench for longer lever, that would be "overtightening with hand tools"

.. some googling for torque value returned:

Manual reference number: AIM 004 425 - 4
https://www.toyota-tech.eu/Aim/Aim2.aspx?pubtype=AIM&menuitem=1
https://www.toyota-tech.eu/aimuploads/9001c475-3fa4-4bb5-994d-86f55a1f54d2/Torque_values_for_Alloy_wheels_Steel_wheels_Wheel_lock_Toyota_AIM_004_425_4.pdf
GT86    Mar'12-         Wheel Nut Torque (N*m): 120     TPMS/TWMS Torque (N*m) 4

For aluminum aftermarket lugnuts it might be less, who knows.

I don't think that some water getting in might be at fault. Exactly for that these are -closed-end-lugnuts-. Now sloppy tire tech that cluelessly impact overtightened imho is much more possible :).