If you over tighten the bolts they will yeild and eventually fail. Other than that the bolts could have been defective.

I had this happen with inner CV bolts that would stretch and bread before even getting to the specified torque. I double checked my torque wrench calibration then tried one of the old bolts and it tightened up fine. It must have been a bad batch of bolts that were made of the wrong material or not heat treated correctly. Poor QC FTL!

'95 S6


'90 G60 Corrado 2.0L 16v Supercharged