Most of my cars have lug nut torque specs from 75 to 85 ft-lbs.
At least if you got car jacked they wouldn't have gotten very far with only 3 wheels!
Wow thank you. You must be a scientist ? Thatās pretty cool thatās a lot of insight and detail. He torqued all of them to 150 all new lug nuts. The front wheels lugs were so tight the battery powered wrench couldnāt break them loose he had to use the air gun. Iām going to go talk to the manager at that location they need to be torquing these lug nuts properly. Iām glad I didnāt crash and Iām glad that the car didnāt get damaged on and off that flat bed with just a single lug nut. The tire was sticking out completely crooked I thought it was going break off.It'd be nice to see an in-depth, scientific analysis done. The last one I looked at was from wheel stud failures seen at a racing school that many of you here were privy to by purchasing the very car that brings you here. The failure mode there was of a different type but the breakdown was eye opening. I can't share the results but they were definitely not what was expected.
Internet quarterbacking here requires a number of assumptions which really isn't fair in terms of an genuinely scientific and accurate assessment but since that seems to be the way the world operates at the moment, I'll take a crack at what I see. I'll assume the studs were installed properly (pressed and not pulled) and fully seated along with none of them being defective.
Right off the bat, and a question to the OP...was the aftermarket wheel you used hubcentric but to a different diameter than what Ford uses in this application? I ask because I see what looks to be a nylon spacer slid onto the axle hub register.
Not a fan at all of this type of "solution" but I digress. Point being, the loading on the studs could be different than normal (read: bad) if a stud issue allows the minimum required amount of friction between the rotor face/inner wheel hub face to fail to meet threshold and you lose concentricity.
I also see something on the threads. OP, did you or the installer use anti-seize on the threads? Fodder for another discussion that can go off in a number of different directions and I'm just trying to better understand the conditions in this case. I numbered the studs for discussion purposes but you can clearly see something on stud #2 and evidence of such in the same approximate locations on the remaining studs.
If my eyes are right, my thoughts lead to what torque figure was used. Anti-seize isn't the best lubricant for this application (scatter) as it can lead to inconsistent and thus inaccurate tension being applied. We don't know the methodology used by the installer, ie, torque figure reduction using X% for friction reduction and/or if that target figure was attained when installed. All we have is a picture.
Of a number of scenarios involving the order of failure I lean towards the following. I could see #2 and #3 failing first. This left $1 and #4 to give it everything they had as they now faced the high bar, with #1 losing the contest and exiting next. This left #4 in a weaker state than #5 so it failed next and in a somewhat different mode than the other failures - more on that in a minute. The last man standing, #5, is no doubt on the verge and I suspect microanalysis would show fractures at a similar thread root location as the others.
As to whether the studs were installed using too high or too low of a torque figure...my sense is the error was made in that there was not enough tension imparted and the failure mode was fatigue (this is where the aforementioned concentricty and friction issue can wreak havoc on the fasteners). Failed wheel studs due to extreme and repeated impact gun use often shear at a near 45* angle or have other characteristics such as "necking" (reduced fastener diameter) whereby the overall length of the fastener increases permanently - they become "plastic" or permanently elongated. If that is indeed anti-seize on the fasteners, one might assume that these may have been overtorqued at some point. Tough to assess that one.
It does look as though the wheel holes were somewhat "oblonged." Look closely.
Wheel movement under braking/turning due to inadequate preload on the studs meant there was inadequate clamp load. Wheel studs are designed to be under tension and without shear (a force applied 90* to the stud axis in this case). Studs #2 and #3 show cyclical loading. It looks as if the preload was low as you see on both a large area that is flat and bright as the shear forces dominated and caused abrasion, creating the smooth face. You can see ratchet marks as well (radial arcs on the smooth surface) which indicate high stress concentrations. Stud #4 looks to have started to fail in similar fashion and then with roughly 50% left it failed in tension rapidly and just ripped right off. I suspect this is when the driver really noticed this while driving. Thank God for stud #5, it may have saved a life.
ON EDIT - OP, I would pay very close attention the hardware on the remaining three wheel/hub/stud assemblies. As in removal, vigorous cleaning and inspection. You may have another failure right around the corner if the conditions regarding hardware choice and install were the same.
Yup. A thousand words to say 100.
while we're all guessing, my money is on wheel wasn't mounted flush and flat.