Greetings.
As a retired mechanical engineer who worked a bit with fasteners (although not wheel studs and lug nuts) I thought I’d offer a few points for the group to mull over.
Twisting the lug nut onto the wheel stud induces a a clamping force to keep the wheel on the hub. That clamping force is controlled in part by the torque applied to the nut. But that clamping force is also affected by thread geometry, stud diameter, nut contact area and friction on the threads and the nut to wheel contact surface. Think of the difference between torquing rusty, corroded threads versus fresh, lubricated threads.
The torque level should be specified as a min/max range about an optimum sweet spot for the design, not just a single value. Too little clamping force a.k.a. torque and the nuts can work loose, fretting and wear can occur, and/or the studs could be subject to metal fatigue - none of which are good as you all can imagine.
Too much torque could cause the stud stress to reach or exceed the plastic limit proof load of the fastener. That’s why, Dexter stated a 120 ft-lb limit for the 1/2” high strength grade 8 stud as shown by Mike D. JD described what generally happens when folks inadvertently over torque fasteners.
Excessive clamp load or torque might also distort/damage the wheel but I’m not aware of how this could result in catastrophic failure which is what I think was the concern with the 120 ft-lb specification.
Moral of the story:
1. Purchase and use a good quality torque wrench. Human “feelings” are not a good, well calibrated substitute. And use the recommended torquing sequence!
2. If the lug nut is torqued to or somewhat beyond the maximum limit and the stud hasn’t twisted off, the wheel isn’t going anywhere.
3. Under torqued lug nuts can be a problem. JD discussed torque wrench calibration and the issues for the high side of torque. But a similar issue exists for an inaccurate torque wrench or “human feel” for the low end of the torque range.
4. The proper torque range is specified in SAE or ISO fastener standards for the hub and wheel configuration. (Sorry, don’t have that info available. And BTW, Oliver, Dexter or the wheel supplier need to provide the torque range for the fastener condition.)
If this thread is concerned about the effects of excessive torque on the wheel, maybe we could better detail what we think those concerns are and then reach out to Oliver or the wheel supplier for more specific information.
