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2003 996tt rough ride, can changing tire profiles help?

Wheels and Tires

Vehicle Information: Year: 2003; Body Type: Coupe; Total Mileage: 8000;

I have owned many Porsches over the past 50 years and have never been Porscheless for long. In the last six years I have acquired a 1997 CR5 a, 2000 Boxster S, a 2001 Twin Turbo with Tiptronic, and a 2003 Twin Turbo with Tiptronic and the X-50 option. My current Porsche came dealer equipped with 19-inch wheels (9 1/2 wide front, 12 inch rear). I love the appearance of this combination; however, after 8000 miles in five months I came to the conclusion the small 30 profile P Zero tires on tall wheels resulted in a very rough ride. I have since reverted back to the factory stock 18-inch turbo hollow wheels, which are shod with Pirelli P Zeros and mounted on 225 x 40 on 8-inch wide wheels and 295 x 30 on 11-inch real wheels. This change of wheel and tire size combined with less weight has definitely improved the ride on back roads with rough surfaces. Still my honest description of touring continues to be rough ride. I do not plan to put this wonderful machine on the track very often; therefore, I am looking for a reasonable way to improve upon the comfort and high performance touring characteristics of what I regard one of the finest cars ever designed.My question to you is, Can I achieve an even better rear soft ride by increasing tire side profile size on the rear of the car without disturbing the computer set up on four wheel drive considerations? All Turbo cars seem to come with 30 profile tires on the rear. An increase of 35 to 40 profiles would probably provide what I am seeking. Several other senior PCA members have expressed similar sentiments.For example: I would like to consider a substitution of Michelin Pilot Sports, which are available in the following sizes:225 x 40 x 18 or 225 x45 x 18 front285 x 35 x 18 or 295 x 45 x 18 rearIs it possible to safely increase the rear side profile size? If so, can I simply go to a 35-profile tire on the rear? This may be a dumb question but the two largest Porsche dealers in Florida give conflicting answers.Possibly an additional benefit would be the fact that most rear high performance Z rated tires only provide eight to 12 thousand miles on 4wd Turbos before going bald or noisy. Perhaps a touring set up when average speeds are well under a 100 mph average would be rewarded with quieter and improved mileage?After many years of enjoying Panorama this is my first inquiry and I wish to express my sincere appreciation in advance for any suggestions or assistance rendered.

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