I checked the R107 part number - they just use the basic donuts. Having an internal spring or chain would be a help when the donuts break!

No, they don't .

Try the correct factory ones, you'll see .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better