Q I’ve just fitted some new wheels and wheel nuts, but there doesn’t seem to be much thread going into the nuts as the new wheels seem to be much thicker than the old ones. I’m using the nuts I was supplied with. How much thread engagement do I need to be safe? Geoff
A The mechanical standard for minimum thread engagement for optimum strength is 1.5 times the thread diameter. So for a Mini wheel stud with a 3/8-inch UNF (0.375-inch diameter) thread that would be 9/16-inch (0.5625-inch) engagement. But with wheel studs and nuts I would look for more than that. I don’t know if there is a specific engineering calculation for this, but I would look to get at least twice the diameter in engaged thread length. So 3/4-inch (0.750-inch). You haven’t stated which wheels and wheel nuts you are using, but where a standard type wheel nut is used, I would want to see the end of the stud at least flush with the outer end of the wheel nut.
Wheel nuts need plenty of thread engagement to be safe.