2eXceL

iTrader: (2)

The issue for the broken bolts is most likely due to the selection of grade 12.9 NOT the torque, although the torque is also questionable. Grade 12.9 is never used by OEMs for anything other than engine heads or engine parts due to the high degree of brittleness in the 12.9. There is no reason why this application should be anything other than grade 10.9 max, look at most of your suspension components and you will see this is the case. A very brittle Bolt is the LAST thing you want in a suspension component that takes vibrations and flexes.

GSteg

iTrader: (15)

I wouldn't necessarily blame it on the brittleness of the fastener. Improper torque is most likely the culprit. If grade 12.9 failed, then grade 10.9 would also have failed.