In Reply to: So, about these Volvo caps and rotors... posted by Jon on January 25, 2002 at 17:18:47:
"I do notice that they always list another PN for M3 rotors but nobody has a picture of that one."
The other rotor (not pictured) is the one I think will work with the Volvo cap. It appears identical to the M3 one in the picture, except it has a flat contact in the center instead of a hole.
BTW, I did see some bolt on rotors in my search of Volvo parts, but they still look quite different from the M3 rotor.