Stopped by the junkyard today after work and pulled the rear rotors (and pins) from the s70 that donated my replacement hood.

I checked the form, fit, and condition and bought the pair for $30.00.

I pulled the rear rotors off my c70 and realized that the rotors were identical (although the replacements are thicker). The hub has a slight male cone at the base that centers the slight female cone of the rotor. However, the rotor doesn't fully seat until it is held tightly against the hub and the potential for it to go a little bit askew is much higher with the aftermarket wheels.

I found that even the pin did not prevent it from seating incorrectly and used the lug bolts to center everything.

I put the pin in, removed the lugs an installed the wheels. Since these are aftermarket wheels they have holes for 5x108 and 5x114 (I think). I was lucky to find the point where the hole for the 5x114 fit cleanly over the index pin. I torqued everything down and it all seated correctly.

This is a nice success and helps things. Unfortunately the "shrink-shrink" noise is still there when I drive the car, suggesting that the problem is either the e-brake shoes (one of which lost it's pad when I pulled the rotor) or the thinning rear pads.

The noise reminds me of when I let the 940's rear pads run down to metal... except that the pads still have a little life... Arg. I'll have new rear pads and shoes in the mail tomorrow, so I'll post back if replacing the pads doesn't stop the noise.

Thanks for the advice!