RENNsport said:
If it did happen while you were doing donuts, it is not your fault. It would have broken regardless because there is a manufacture defect.
On every single H&R kit for the E46 M3 that I have seen, there has been a problem with the rear spring perches breaking/cracking. We refuse to sell H&R coilovers for that model car because of that. You can contact your H&R dealer for replacement of the part but there is no guarantees that it will remain intact.
I think what is refered to as the tensioner is the 2-pc spring perch which is what enables you to adjust the height.
The H&R perch cracked on my E46 M3 passenger side. However...H&R did send replacement perches for both sides. I inspected these perches and they are re-designed and much thicker and stronger.
They also provide you with a plastic washer that goes in between the spring and perch.
I would think they put this in their new coilover kit by now.
In addition, I know somebody with a 330 that had this same problem also...so I don't know if it is limited to the M3's.
This problem is with the older perches from H&R...I think the new ones are good.