Yes, it was the rotor size. I went to O'Reilly today to get new rotors, and their computer supports the use of both size rotors in the SSEi. And the smaller ones can work, as I have used the smaller ones for the last 3 years.

Put the new rotors on along with new pads. Because AutoZone took in trade some old pads I purchased there in 2007 (and gave me back $6 in cash), total cost of ceramic pads and Wagner rotors was under $75.00.

Attached are pictures of the small and normal size rotors, smaller on top.

Good thing you caught that. I can't imagine what would have happened a year down the road after using only 80% of the pads.