For summer tires on my '05 Boxster S, I am really happy with the Michelin Pilot Sport 4 S. Stock sizes for 18" wheels are F 235/40/18 and R 265/40/18. Quiet, grippy, and really impressive in the rain.

I recommend stock sizes and pressures as shown on the door jam. Good luck!

 

Seconded...Pilot Sport 4S. If you aren't tracking the car you don't need an ultimate summer tire which is going to be noisy on the road and sketchy in the rain.

 

 

There are numerous reasons for a staggered setup. The biggest reason is traction. It's a rear wheel drive vehicle and all the torque goes through those two wheels on its way to the ground. Then you get into vehicle dynamics and handling balance. A larger rear wheel gives you a larger contact patch at the ground. It makes it a little easier for the tire to support acceleration forces while also supporting cornering forces, so it can accelerate better out of a turn.

Your car should have narrower tires on the front and wider tires on the rear. If it doesn't then someone put the wrong size tires on the front of the car. I think the SUV's are the only thing Porsche sells with equal size tires at all four corners. Every 911, Boxster, Cayman, 718, and Panamera will have wider tires in the rear.

 

As above. The stagger designed by Porsche is deliberate and highly recommended. Frankly, there's nothing like a few hundred million euros of development.

Double check the sizes F/R. They should be staggered.

My recommended starting point for these cars is to set them up exactly as designed from the factory (tires, alignment, maintenance, parts, etc.). With that you get the designed driving experience and performance which, by the way, is pretty awesome right outta the box.

Good luck!

 

Another vote for the 4S. Great tires.

 

 

Considering that we don't need winter tires in Georgia, the PS4S is also much suggestion. Pricy, but good performance.

We don't deal with ice and snow very often (when we do, we just stay home in GA...), but we do get temperatures well below freezing. Tires like the PS4S are not advisable when it's below 40° F because it can damage the tire.
If you store the car in a "warm" garage, then you'll be fine to drive when it's below freezing. The tire will warm up as you're moving. But don't leave the car parked for long periods of time in low temps or parts of the softer rubber can start to crack on some summer tires.

All Seasons tires provide terrible grip all year 'round, but there isn't a significant difference in grip from hot summer to cold winter.
Summer and performance tires have an optimal temperature range and can be a lot more slick when it's cold. While not any more slick than a cheap all season tire would be, the dramatic difference in grip can be unexpected to the uneducated driver. So it is a fair warning.

Take some time to do research about tires... Tread patterns, tread wear, rubber compounds, threading, sidewall stiffness. If you're only interested in a tire that "looks cool," then you need to understand the differences between a performance tire like the PS4S and a cheap Nexan Roadian that could look the same to the uneducated eye.

Make your purchase based on reviews on Rennlist and not based on reviews on tire websites. You'll get honest opinions from people with the same car on this forum. On general tire websites, you get reviews from people driving minivans at 15mph under the speed limit with their radios blasting. They'll have no understanding of wet/dry grip or tire noise, but they'll give an $80 tire a 5 star review because Walmart made the buying process easy.

As for the purchasing process. I always buy my tires from trusted online sites (simpletire, tirebuyer, onlinetires, discount tire's ebay store, and even Amazon) and take them to a trusted shop to be mounted. You'll have to pay a mounting and recycling fee, but this is almost always cheaper than buying tires through the dealer or tire store. Just make sure you're buying new tires that were manufactured within the last year and leave the labels on the tires when you get them mounted.
I would suggest TireRack, but since you live in GA, you'll be stuck paying both sales tax and shipping which can negate their discounted prices.

 

All Season tires are no longer as terrible as they used to be. Some of the newer "Ultra High Performance All-Season" tires are very acceptable for cold weather or even all-year driving (obviously not for track time duty!); for example, the Continental ExtremeContact DWS 06.

And TireRack now offers free shipping on any purchase over $50.

 

Go on to the tire rack website and check off the boxes that appyly to what you want. Then decide how much you want to pay. Narrow it to three choices and then ask. With what you asked, the typical answer is the most expensive is the best,which it may be, but also may be more than you want.

 

In the past, Tire Rack and other "wholesalers" have held a significant pricing advantage over all but a few brick and mortar tire stores, but that's not necessarily the case anymore. For the past several years, my local independent tire shop has consistently beaten Tire Rack's prices, sometimes significantly so, on a variety of tire sizes and brands. I just had them put a set of PS4S's on my Cayman and my drive-out price (4 tires, taxes, mounting/balancing and tire disposal fee) was almost $50 less than Tire Rack's posted price just for the tires (and which did not include taxes, mounting/balancing, disposal, etc).

So, certainly utilize the Tire Rack's selection tool, but before you order, check with your local tire shops for pricing. You may be surprised.