2006 Mazda RX-8 Sport — question: Inside shoulder wearing much faster than rest of tire

2006 Mazda RX-8 Sport, about 151,000 miles. Front tires look fine from the outside but the inner shoulders are nearly done. Car is lowered a little. I'd rather fix the alignment than just keep buying tires—what measurements should I ask the shop for besides toe? Any data points from owners would help.