I ordered my 6MT last week and try to swap the tires when the car comes in. Should I stay with OEM 215-55-17 Good year Eagle GS-D or bigger tires 235-50-17 like Michelin Pilot sport A/S.

 

Mine (5AT) came with the Bridgestone Turanza's. I'm driving them into the ground before replacing (8200 miles on them and they're just about shot -- autocrossing once a month tends to do that). The Pilot Sport A/S is a good choice. Also available (in 225/55R17 sizes) are the Bridgestone Potenza S-03 Pole Position and Goodyear Eagle F1 GS-D3, both good summer tires. Since I'm in SoCal, I don't need an all-season tire, otherwise the Michelin might be my choice.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

I haven't decided what summer tire brand I'll pick when the stockers run out (can't wait), but I'm sure i'll go for the larger 235/50x17 size. I purchased this size for my winter set, even though I was looking for narrower tires, because of selection in this size of both brand and speed ratings. The slightly wider tires look great and feel good too. Size difference is less than a quarter of one percent smaller compared to stock, a near perfect match.

2003.5 G35 6MT Sedan, Desert Platinum, Aero, NAV, Winter