Ok just one last time. I did do a thread search and found a post about a year old discussing the issue of running 18 inch rims on the 997-3. the issue at hand was the risk of running into ABS or other electronic issues on the 997-3 by changing the wheel diameters going to the 18 inch rim. Generally I think people found that going to the 245/40/18 or 255/30/18 front and the 335/30/18 on the rear, was close enough.

However the Nitto which I want to try the closest combination is 245/40 and 315/30/. as you can see with the 245.315 combo the front is actually larger in diameter. from what I can see some people have run this combo with out a problem. I would just like to hear someone say that they ran that exact combo and did it without a problem?? anyone.

If I go to toyo i can get all the sized below, only bold in NITO NT-01

Front
P245/40ZR-18 25.7
P255/35ZR-18 25.1
P265/35ZR-18 25.4

Rear
P305/35ZR-18 26.3
P315/30ZR-18 25.5
P335/30ZR-18 26.0

 

What about using the 255-35-18 Nitto up front? That size will fit fine on an 8.5" wheel, and although the total rolling diameter is smaller, the side wall height should be very similar to the stock 235-35-19...giving you a crisper turn in over the taller 245-40-18 size. Plus, you'll have a little more meat up front to help out with understeer. I guess the question is, will the smaller rolling diameter pose the same problem for ABS as a larger one?

I'm in the same boat as you, where I want to try NT01's on my front 9" wheels, but they don't offer 265-35-18's....only 245's and 275's.

 

Ran through 2 sets of Nittos 245 and 315 on a 996 turbo with no ABS problems and no viscous coupling problems either. I would think ABS system would be similar on both cars.

 

Those tires will be fine. The ABS is looking for a differential in speed between each wheel. As long as the overall diameters are close they work. The problem happens when there's a significant difference in diameter between the front & rear tires. I'm not sure how much margin is programmed in, but I know a 1/4 inch diameter difference (25.5 & 25.75, for example) will be fine.

 

also, it's sort of curious why there's a lot of 19" wheels & tires for sale, and many wanting 18's.
Is it possible that for ultimate performance 18's ended up being the best in terms of tire to rim ratio?
19's and up are more to satisfy bling seekers?
You have to figure with all the upsizing in rim diameters over the last decade or so, that eventually the law of diminishing returns would come into play.
Just curious, that's all.

 

My motivation to seek out 18 inch solution is two fold, cost, and different tire options. Except for the R888 all options on the 19 are more costly but really I wanted to try the Nitto and they do not make a 19 and the 18 nittos are so much less expensive. And its fun to experiment. Another big plus to 18 could be weight but that depends on the rim combination.

 

I've been running 18" Toyo RA1s 245/40 front and 305/35 rear with no problems. I've have PCCBs with CCW C10's.

 

What is the height of the stock 19" with 235/35 - 305/30?

 

Aren't rolling diameters only a problem on awd cars?

 

Can be a problem on 2wd because of ABS & PSM.

 

Tell me about the R888's in the 18" 245/305 combo versus the 255/315 or the 265/305? Has anyone tried all of these? I'm tempted to go with 265/305 or 245/305 because the heights run closer to stock.

 

As long as the diameter difference between the front and rear is no more than 4% PSM and ABS will be fine. I always tracked in 07 997S with:

Toyo RA1
245/40/18 front
305/35/18 rear

or

Toyo R888
255/35/18 front
315/35/18 rear

These were mounted of CCW 9x18 and 12x18 C14's

 

OEM 19" MPSC diameters:
frt 25.5" and rear 26.3"

R888 18"
245 = 25.7
255 = 25.1
305 = 26.3
315 = 25.5

R888 19"
235 = 25.7
305 = 26.5

Hoosier R6
245/35/18 = 24.7
315/30/18 = 25.6

 

Thank you Grey.

 

255/315 is the set-up