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Sorry for the mini-hijack but I am about to pull the trigger on tires in this size myself. What are the current thoughts on the PS Cup 2 vs. the PS4S for a purely fair-weather weekend/canyon street car? I have run DOT-R tires year-round on other street/track cars for many years, but never on a modern 911 thus far, and never the Michelin Cup/Cup2.
Also been running 245/325 19" combo on 8.5"/12" BBS wheels for a couple seasons now. Not a single issue with fitment, clearance or front diff. Changed the front differential oil earlier this season (original 10 year old fill) and the oil came out golden and clear - almost like new.
Be sure that the offset on the wheels are low enough that the wheel and tire are pushed out to be flush with with fender - see my avatar. This will ensure you have lots of clearance on the inside.
And FYI considering it's related to this topic - technically the 245/325 combo is not the same front/rear rolling diameter as the stock 235/305 setup. It's close, and the general consensus is that it's within whatever tolerance Porsche may or may not have allowed from the factory to account for winter tires, worn tires, etc... The technical match to the OEM F/R ratio is 255/325 but 255 doesn't fit nicely under the front of a 997.1TT. However, those of you with a 997.2TT, they fit just fine as the fender liner is slightly different in the .2 allowing for some extra space.
Someone should be the guinea pig and buy new or used front .2 liners and see if they fit in the .1 wheel well. Then .1's could run the proper 255 front tire. I don't recall anyone trying this out yet.
I'm running GT2 wheels and tire sizes without issue and it looks awesome on the car.
However, I would not suggest Cup2 tires... mine came from a very large name company and proved to be old stock... coming with that was tires that clearly had been stacked improperly as the fronts (including the newer set they replaced with under warranty) have vibrations at certain speeds... when you see them on the tire balancer you can see the out of roundness of the tire. I should have gone with the Sport 4S or even considered the Continental...