Torque is specified for a specific thread size not to exceed the yield point of the material. Obviously different materials will yield at different points of stress so the torque for a hardware store bolt will be different than the torque for a grade 8 bolt. Lug bolts are generally made from alloys that are similar in strength; therefore we can use a common torque value on them. At the low side of the spec the material begins to stretch thus creating tension to keep the nut from coming loose, at the high side of the spec is the maximum that the material can be stretched before it begins to yield. If you exceed the spec it's a good bet that you have stretched the thread beyond its yield point.
That's the way I view it, now I'm open to hear
"The guy at the tire stores reason is why he wants to torque them to 85-90 lbs. And your mechanics explanation for using 185lbs of what ever on a three foot bar to torque a lug nut.
Denny Graham
Sandwich, IL
