Also remember that your rear tires wear at a much faster rate than your fronts do. Based on hound's example, this would still allow for rear slippage to transfer torque to the front when needed but you wouldnt get the benefit of it doing regularly... however, this would change after only a couple hundred miles as the rears wear in.

 

The above is my current setup, but I wonder if the 225/40R19 or 235/40R19 would be a better option for the front.
225/40R19 = 26.1"
235/40R19 = 26.4"
295/30R19 = 26.0"

Later, Steve

 

So, you're saying the optimum 19" tire combo for an AWD would be to run a taller rear (than the front)? How is that optimum?

Aren't AWD cars supposed to run a slightly taller front?

 

This is taking all equations into consideration:

• Availability of tires (wide selection)
• Fitment (tires wide enough to match wheel width)
• Ware (considering wear, rear wear vs. front wheel wear)

Obviously running a 225/35/19 and 315/25/19 would be great, however the availability of the 315 is limited to Nitto and the 225/35/19 will appear too narrow when mounted on a 8.5" wide wheel.

 

FYI: the 997 Turbo is equipped as follows:

235/35/19 & 305/30/19

So to answer your question AWD cars supposed to run a slightly taller front is not correct, these vehicles are built in their own geometries respective to their design so take the following bit of information for what it's worth.

997 Turbo & C4S Standard 19x8.5 (et. 57) 19x11.5 (et. 51)
Front: 235/35/19 = 25.5
Rear: 305/30/19 = 26.2

 

But doesnt the 997 have a different setup for its trans/awd than the 996? Ive seen a couple times where people state that they can 'now' run larger tires in the rear after they swapped out to a 997 setup.

 

Yes, this was an example to reply to an other person's post...

 

19 inch are horrible on a 996 tt. They perform worth to an 18 inch wheel. 18 inch with michelin pilot sport cup is the way to go for good performance.

 

+1. And they look better 12 in the rear.

 

Except the 235/40/19s don't fit without serious rubbing on the suspension and fender liner on stock height. I bought these in Pilot Sport trim from Michelin and had to return them to run 235/35/19 which just clear.

 

235/35/19 michelin pilot super sport
295/30/19 Michelin pilot super sport
Matte Black Roderick RW-5 wheels

 

For sure, I'll looks for the ET, they are 19x8.5 & 11with 315/25. I'm going to go with the 305/30. I lowered the car a tad so the 30 series will fit just right. I have new wheels coming soon.

 

There are a ton of variables left out here.
- What were the offset and width of your wheels? This and spring diameter could easily be the cause of it rubbing the suspension.

- Where was it rubbing on the liner? Inner, outer, or evenly?

Yes, the larger diameter tire and some adjustments may need to be made but I havent heard anything from others about serious rubbing with this tire size.

 

Wheel offset

19x8.5 ET 45
19X11 ET 40

I can’t remember at what turn ratio the steering wheel was at but it rubbed on the front inner fender liner towards the bumper during fitment (there is a little bump out you’ll notice if you look)

You are correct, it was the large diameter of the spring cup support that the sidewall of the tire was contacting when the vehicle was in the air. I could tell that when the car was lowered that this degree of contact with the suspension wouldn’t get any better.

If you think about it the 235/40/19 puts the front at 26.4” tall when the OEM 18” diameter was 25.1”. That is a big increase in height. And comparing offsets with the new 8.5” wheel vs stock the new offset only put me closer by 1.3mm towards the suspension (less than 1/16”) which is really negligible.

Not to say that this size can’t work but it means that if you run a 19x8.5’’ wheel with this tire size you would need to modify the fender liner and run spacers. Also IMO the 235/40 sidewall height didn’t look that great with the 19’’ wheel.

When I bought the car it had the 997.2 Turbo II Look wheels on it with 305/30/19’s on the rear and the same 235/35/19 fronts. At least the 295 is a little closer now than what it was before. Grip wise, this these tires are phenomenal.

The 235/35 works for me, I don’t plan on tracking the car any time soon, but if I did I would just run the OEM Twists since paint and wheels take a beating on the track, and they perfect diameter from the factory for the 996 AWD.

I haven’t had any problems so far on the street, it’s not my daily driver. And looks wise the 19” updates the car a lot more.

 

I definitely agree that its not optimal. The sucky part of the whole thing is that proper sizes for our car (in both 18 and 19) are getting harder to find. Im going with the mentioned sizes because its the only good ratio for the S-04 out there and its an amazing tire (especially for the money). Doing the slight mod to the front bracket isnt that hard if that is what it takes.

Id run my hollows for the track as well but first I need to find a good shop to strip the chrome off of them and refinish correctly. Thankfully that was the only gaudy thing about the car.