FYI
For anyone considering to change tire sizes on the car.
I have the 19" Champion Magnesium wheels.
I had my Porsche tech upgrade my rear tire size to 315.

Hard to imagine, but such a small change in the rear tire size caused the car to be extremely unstable under acceleration. the Torque twist on the steering was so much that I had to switch back to 305.

 

Hey Shashi,

You must have never seen this thread by Fred!

https://www.6speedonline.com/forums/...hlight=warning

 

Correct, you can not change the ratio that much.

 

Once again... 315 is the width. It has nothing to do with the heighth of the tire. If you get the correct sidewall height in a 315 wide tire, it will work.

Example:
315/25zr19 is 25.2" diameter
245/35zr19 is 25.8" diameter
As long as they are within 3% of each other, the factory gearing and computer will still work.

 

stock rear height is 26.3". There is no current 315 that would fit the rear when using the stock fronts. If you use the 315/25 then you would need something shorter in front like a 235/30 or 245/30

 

That makes sense. I just get frustrated when I hear people just use the width when describing a tire.