thank you! glad i could helpForgot to say, I swapped out for 325s in the rear when I did that. You lose that stretched tire look in the rear and it matches the poke from the front better. Look for pics I've posted and you'll see what I mean. Also, look for pics @Prokiller put up (this one kept me going while I was waiting for my car to be built )
Put less than 30 miles on the PP2 OE Michelin tires, then swapped them out for Continental Extreme Contact Sport tires. Kept 305/30x19 on the front, but upgraded the rears to 325/30x19. The slightly taller 325 tires increased ride height by +/- 0.25" but was offset by the installation of Steeda springs (555-8243). I have no plans to track the car so absolute adhesion is not a primary factor, but having the 340 wear factor is. Ford indicates a skid pad rating of 1.06g for the Cup 2 tires. We did a 'quick & dirty' skid pad test & got 0.997 w/the Continentals which pretty much relates to zero difference on the street. Plus, the 325 tire most definitely fills out the rear tire well & (as m0.s550 indicated) "it matches the 'poke' from the front better."I'm sure a few of you have swapped the OE Sport Cup 2 tires out for others & wanted your input.
Your contact issue w/the 325 tire is a wheel offset problem, not a tire width problem. I have Continental 325/30x19 tires on OE PP2 11" rims on the rear w/zero issues. If your existing rim is offset too much to the inside, even a 305 tire may not work. Hopefully someone on this site w/the exact same rim as you have can verify a 305 tire fitment. Both Michelin & Continental recommend a 10.5" to 11.5" rim width for their 305/30x19 tire. One final thought ... a 305 tire mounted on an 11.5" rim on the backside of the S550 Mustang (especially a GT) may present some unique handling issues. Maybe someone out there can provide more concise information on this (potential) issue.... sadly the rears hit the Magneride w/the 325 Toyo tires. Anyone know if I swap out to the SC2 305 width would it be stretched too far on an 11.5" wheel? I'm thinking the less wide tire will give me the ~10mm clearance I need w/out going to a spacer.
...Plus, the 325 tire most definitely fills out the rear tire well & (as m0.s550 indicated) "it matches the 'poke' from the front better."