I've gone through all the threads and there is a lot of theories on total wheel diameter % causing issues with the AWD differential. Don't really need to get into that cause it's discussed in heavy detail all over the forums.

But can someone confirm if this is a 996 issue only? As the 997 differential is using a electro magnetic control as oppose to to the 996.

Obviously not going to go extreme. Sticking with 235's in the front, but wonder if I'd be free to go between 295-325's if I wanted to without worrying about differential burn out.

(996 Discussion - https://www.6speedonline.com/forums/...e-se-up-3.html )

Thanks!

 

The differential on the 997.1 is a viscous coupling link, which is identical to what was used with the 996 series.

I recently changed all the tires (Pilot SS) on my C4S and noticed an improvement and a reduction of the noise due to the coupler, especially when you do rear maneuvers in parking lot. My previous set of tires PS/2 was very good in the front and super slick on the rear. I suspect it was causing the coupler to react under certain conditions.

The coupler is supposed to react extremely fast according to Porsche.

I believe the 997.2 and up have the magnetic/electric coupler.

Again, I am not an expert and do not drive my car hard. In addition, it has not rained since I changed my tires and cannot comment on the behavior of the coupler when the rear wheels are slipping.

Yves

 

Thanks Yves - 997.2 makes more sense.

What where the tire sizes with the PS/2 and now?

 

I went with the exact same size in 19" rims (235 Front, 305 rear).

Big difference in price between the PS/2 and Pilot SS, though...

Yves

 

For a quick comparison of tire sizes I find this site very useful. It doesn't tell you the size of any particular tire, but does show the impact on circumference when varying the profile and/or width.
http://www.tiresizecalculator.info/

 

Thanks Ken.

I'd guess the differential is made to tolerate a certain ratio. With the OEM tire sizes at 235 and 305 (or even 295 for that matter) they are around 2.75% apart in diameter.