your best bet is to take the part out and have it put in at a machine shop..I had mine done that way..the regular tire centers had a problem because there is a curve in the arm and they didnt have the tools to put the new one in..they could get the old one out.(my Benz dealer wanted $100.00 if I took the arm in and $400.00 if I had them do it)
that way it only cost me $30.00 to have it put it..it works fine..
hope that helps
1982 380 SEC