Just for the clarification, 06 S Titanium Edition offered with staggered 20" sport-technos which came with 275/40/20 as an upgrade option.

Got this from the internet, but you get the idea:

 

^^^^^Those are the wheels I have on my 04 S.

 

Porsche sold them as an option on many models but most of the time it was in 9" front and rear. Only a couple of years was it offered in 9" & 10" staggered (besides being stock on the CTTS). The staggered setup looks almost the same but as mentioned above the rear is slightly concave.

 

Almost the same, yes, but drastically changes the look, IMO. A look for the better. I am going to come full-circle and say again that it is bizarre that Porsche offered this while utilizing the same size tires all around. Maybe it's just me.........

 

They were definitely staggered.

 

I own a 2006 CTTS. Stock wheels are 20x9 front and 20x10 rear. Originally it had 275/40-20 all around. I've upgraded the rears to 315/35/20. Key to this working is the diameter matching on all 4 tires. If you research you will find that 275/40-20 and 315/35-20 are designed to be the same diameter. FWIW these were the stock size tires on the BMW X5M.

Here's a picture of my rear wheel with the 315/35-20. Very nice look to it.

 

Here's the wheels laying flat on the ground. You can see the 20x9 with the 275/40-20 tire next the the 20x10 with the 315/35-20. I would add that there is also a very different offset on the 20x10 resulting in a more concave look. You can see the difference in the profile of the wheels in this picture.

 

Looking at the numbers that I've checked minimum rim width for a 315/35 20 is 10.5"

 

Not all 20" Sport Technos were staggered. My 2004 CS came from the factory with the Sport Techno option and they were 9x20 all the way around.

 

So if a 315/35 20 requires a 10.5" rim width, and the rear rims are only 10", what's the best choice for a tire for the rear?

 

I did run a Cayenne S up to 110k miles, with OEM 20" Techno. My first two set were 275 all around, but, my 3rd, 4th, and 5th were 275 front and 315 rear, and I was more than pleased of the handling.
The rear, 315x35 on the 10" wide look perfect, or, ..much better than 275x40 on 10 wide, that exposed the rim to the curb big time.

Also, towing a heavy boat (a Cobalt, i.e.: around 6'000 lbs with the trailer) I can insure that the handling on towing was a lot better on 315, ..than on 275. ) I'm talking about multiple rides like San Francisco to Newport Beach, or 400 miles.
So, in my side, I enjoyed the staggered setup, particularly when towing.
Since I sold this Cayenne S, and have now a CTT with 20" "RS Spyder" 9" wide front and read, I already look around if I can find 2 "RS Spyder" rims, 10 wide for the rear, ..to go back staggered !
If I cannot find these, I plan to quit these rims in order to go back to 20x9 front and 20x10 rear and run with 275x40 and 315x35.

PS : for those that think that 315's on 10 wide looks "bad", here is a photo to show that the walls are very well shaped : (A LOT better than 275's, ..that looks ugly on 10 wide !)

 

Hey I am wondering...I tried 315 on my rear 10" wheels, but the handling is very very bad...sweeper curves at 70-90mph set off my PSM very strongly. Lots of "wag" when rocking the steering wheel back and forth on the freeway, lots of trouble setting up a line thru a curve. With Sumitomo HTS 02 tires at 275/40, the handing is very very tight...what I expect from a Porsche. Pushing sweeper curves would sometimes get the PSM light to blink, but no noticeable affect on performance, just a very mild correction to the rotation that I couldn't even feel! I may just go back to this because I know it works.

What brand tires are you running? I have cheap tires now (to try out the size) by Accelera. Are the tires my problem? I like the look of the tire on the wheel very much but that doesn't matter if the handling is all bad. Do I just need stiffer sidewalls?

I still have 275s up front...they still seem to point the front end perfectly, but the back wobbles around until the g-forces push the rear down into the curve. Then when slowly accelerating and building speed...bam! the PSM cuts off all the fun...or saves me from crashing...or just doesn't like the tires? Help!!! Is the wag far enough out that the PSM thinks the car is over rotating? Or am I just sliding these crappy tires and PSM is saving me?

At this point, I'm almost afraid to hook up my trailer...but I'm trying to find larger tires because of the trailer...d'oh!!

 

 

Hmm, the tires I got are 110W, XL rated. The tires I had on before were Sumitomo with 106 and no XL rating...

The experience you describe is what I'm after...I don't know what I would do if I spent $250 per tire and had the same problem...

 

This 08 TT i just pick up has Sport techno 20in 9 front and 10 rear. ... My old 09 TTS had 21in with 10in/295 on all four corners ..

I am wondering if correct for the sport techno 275 fronts and 295 rears.. The DWS Conti has both sizes in stock... Are these the correct tire size for these rims?