17" vs. 18"

[hamstur]

Here's how to read your tire...

205/50/17 means 205mm width, 50% sidewall aspect ratio, and 17" rim size, so 50% of 205mm = 102mm / 25.4 mm per inch = 4 inch sidewalls.

Your tire will compress about 30% when mounted, so 70% * 4 inchs = 2.8 inches, which means your 2.75 inch measurement is correct.

The OEM front tire for a 996 is 225/40/18, so their height is: 40% of 225 mm = 90mm / 25.4 mm per inch = 3.5 inches * 70% = 2.45 inches.

Porsche does not recommend 19" on 986s and 996s because of the car design...the harsh ride and vibration caused windshields to crack. So...the answer to your question is yes, the sidewalls on the 18" tires will feel stiffer because there is 0.5 inch less sidewall.

If the tires are a bit wide, you would have to shell out a couple hundred for spacers.

Hope this helps,
Andy

[Perfectlap]

I fear 10" rears because they require spacers, and those are not ideal for raced/hard driven cars. The fit has to be PERFECT and even with a perfect fit there is more pressure on the wheel bearings which are ridonkulusly expensive for this car.

[Allen K. Littlefield]

Thank you all for responding. I never liked the idea of spacers as I remember the wide bodied 911 guys that used spacers and they were never satisfied. I like the ride and feel of the 17" rims that I now have and the ride is firm but not harsh unless the road is really bad but that cannot be helped. I do love the look of the 18" and Porsche did offer them as a option (Porsche is now offering 19" on some cars). I notice a lot of guys on this forum have switched to 18" and some are "cheating death" on 19", I wonder if they are experiencing problems?

AKL

[Thumper]

When I changed out my 17" stock wheels for 18" Gemballa Competitions, I honestly could not tell any difference in ride quality or handling. But then again, I don't track my car......yet. The front's are 8.5" wide and the rears are 10" wide. No spacers were required and they fill out the fenderwells perfectly. Spacers may be required with Porsche wheels, but an aftermarket wheel can be bought with the correct backspacing so spacers aren't required.