we had, in the past, one or two problems with cars returning with loose wheel bolts , not me thankfully. i was recruited to address the staff with a dissertation on wheel bolt torquing. i gave the obvious spiel about making sure to remember to torque bolts and `imagine your wife and kids in the car`. also, and MOST importantly, i pointed out the problem with threads in hubs suffering corrosion and corrupting torque wrench readings. this problem is most pronounced with w210 front hubs, now we always (i hope, you can lead a horse to water etc..) clean out the threads on hubs before fitting wheels. MB don`t have this problem so much, what with never taking the wheels off and zapping them up with the gun if they do (bonus mentality). i have never seen a bolt sheared from too much torque, but have seen many of the elongated bolts snap off on removal due to too much torque and dirty threads!