How much can I safely over-torque lug bolts?

[shertex]

Finally got a nice floor jack so I can do my own snow changeovers.

Both my W210 and W211 have newer/shorter lug bolts (thankfully). I have two torque wrenches: an inexpensive click type (Great Neck) and a Craftsman beam type.

Did the W210 this morning. Tightened according to correct pattern first to 70 ft. lbs. then to 80 using the click wrench. Then I went around and checked with the beam wrench. Some bolts, as I hit 80, seemed to tighten a bit more.

I'm not a shop with periodically calibrated high quality torque wrenches...just a guy in a driveway. I'm more concerned about safety than over-torquing a bolt. Yet I am well aware of the headache and expense of overtorquing a bolt to the point where the head breaks off.

So the W210 spec is 80 and the W211 is 96. If I wanted, for the sake of safety to exceed the values by a little bit, what would anyone recommend? Or should I simply trust my wrenches and get it as exact as I can?