I have the same metal shielded bearings from Stella in my Sherman and unless they advertise plastic safe grease, it's not. I just did what YHR did and cleaned mine in rubbing alcohol and then oiled them with the safe oil/grease. Only you can decide which way to go and what environment they will run in.

RC Boyz does advertise plastic safe grease and that's what I have in my Pershing road wheels. I didn't bother with the torsion bars.

HTH


Jeff