I find it hard to believe that an all season tire will handle better on dry roads than a max performance summer tire (OEM Potenzas)

 

That makes the false assumption that the OEM Potenzas (RE040) are anything more than a POS.

Now, if you're comparing all-seasons on dry roads to, say, Goodyear Eagle F1 GS-D3, or Michelin Pilot Sport, or Pirelli PZero System Asimmetrico, or Yokohama AVS Sport, then of course the max performance summer ones will stick better. They'll also tramline more, which is part of 'handling', so the all-seasons have an advantage there regardless.

 

245/40/18 is a smaller tire - the width is bigger but there's less sidewall, which is what affects ride quality. You'll want to go to a 245/45/18.

The improvement in ride was due to an M+S all season compound. The improvement in handling was due to a lower, stiffer sidewall, even though you went to an inferior rubber.

 

Try the tire comparison feature at Tire Rack's site (if you haven't already). I was surprised myself. The Pirellis that Stew mentions are incredibly good tires, and at a (comparative) bargain price. They give up very little in dry traction compared to a max performance "summer" tire, and beat most of the summer tires in a lot of other categories.

Best,
Bill

 

If I'm not mistaken, going from the stock 225/45/18 to 245/40/18 does not change the overall height of the tire by much. It's probably neglible. The benefit obtained must be in the width. The 40 or 45 is the ratio of the sidewall to the width. The wider tires as a 40 are very close to the stock tire width rated as a 45.

 

Thanks again for the replies. I took it to the dealer and they said the ride was normal. Of course that was after I let 1.5 psi out of the tires the day before and told them to fill it to 32 psi which of course they didn't. Anyways, I'll just have to drive with less air for my smoother ride. They also said they couldn't reproduce my seat creaks. Oh well. Still love my car anyways.