Mvez

OK, I have been on the phone with Nitto Tire directly, and unlike some other companies, they are more in tune with their customers, they are willing to create new tire sizes if the demand is brought to their attention. I have discussed with them the need for a 305-35-18 (and the ABS problems that the 315-30-18 creates), and that if they simply made a 305-35-18, that they would sell like hotcakes to the entire 997 platform Porsche community, and corner the market overnight, because in reality we don't have any other options since the RA1 went away, as far as a treaded R-comp is concerned, since everybody dislikes the R888. They already have the 245-40-18 we need.

If you want to run the 315-30-18 rear, then request a 255-35-18 front size.

They have created sizes in the past (for much lower volume cars), and a new one for 2011 simply from requests they get through their website in the "contact us" link. I have no doubt that if everyone who is interested in this type of tire (and not a hoosier) would go to their website and flood them with requests for a 315-35-18, then they could have it available to us for the 2012 track season. But now is the time to start flooding them with requests.

If you liked RA1's, and want a long-lasting DE tire in the 18" size, I promise you this is it. I've been using them on my E46 M3 for years, and they are fantastic. We need more 18" options, so even if you don't want to run them, please go to their site and request the 305-35-18 size. I've been filling it out multiple times a week, but we need different people to request to get this going. Please keep filling this out and help us get the tire we need!

Here is the link directly to their contact page.
http://www.nittotire.com/Contact

cello

You sure its not just a ploy to secure a bunch of email addresses they can sell?

BTW, and as a data point, I run the NT-01s in the 315-30-18 rear 245-40-18 front sizes on a 997.2 C2S and have no problems with ABS, PSM, or any of the other alphabet soup Porsche acronyms; and TracksideData has the data to prove it.

I know about the Internet lore, but have you tried the above sizing to see if there really is an ABS problem? If you have and have experienced a problem, OK; but, if not, it might be worth your time and while rather than waiting and hoping. Just saying.... BOL!

Mvez

Cool, then that means the 35 aspect ratio will work fine for you as well.

333pg333

What would the OD be on the 305/35?

CT03911

I run the same sizes as Cello on a 2004 GT3 and love them.
315/30 rear and 245/40 fronts on 18's.
Great tire- no issues.
I got 19 days out of my last set for $1100 delivered.
Not kidding. 75 heat cycles, very progressive throughout and grippy to the end.

Heat cycle #76 was like I had an oil mist spraying under my car. Undrivable, all from one session to the next.

I have learned more about really driving in the two years and three sets I've had than any other way.
No, I'm not as fast as I could be on MPSC's or HooHoo's but I've learned a lot about really driving, not just going faster.

I agree with Mvez, I understand they are indeed responsive to market desires.

mdrums

So far you're the only 997 that has had sucess with a smaller rear diameter that has posted on any forum. I have not tried it myself but Porsche and so many others that race the 997 platform have said ABS and PSM will not act properly. I believe it was MikeJim on the 997 forums tried the smaller rear diameter and had issues in bumpy brake zones with ABS and so forth.

mdrums

Yep the 996 platform came stock with smaller diameter than front. 997 platform comes with bigger overall diamter than front...996 and 997 totally different in these reguards.

cello

Maybe because I'm the only one that has actually tried the Nittos (and posted of course) ... lol!

Getting real here, the NT01 245/40r18 fronts are 25.55" in diameter and the 315/30r18 rears are 25.35" in diameter. The difference then front to rear is 0.2". The percentage difference then is less than 1% ....

If this difference causes the ABS or PSM systems to malfunction or not work correctly, we probably should not be tracking these cars (what happens as tires wear, front to rear, side to side, etc etc...) I have always heard that the determinative or threshold percentage differentiation, in either direction (ie, not front to rear or rear to front dependent), is 4%.

Anyways, all I am reporting is my real world experience with the subject tires, and the subject tires referenced only, FWIW...

mdrums

You're probablly correct. Thanks for the feedback. I don't have any skin in this trial and error game as I bought 19" track wheels for the GTS. I'm just going to keep it stock sizes and run on Toyo R888, Michelin Sport Cups and try some Hoosiers in the future.

eric523

We have run a 315/30/18 and 245/40/18 on a 2009 997 C4S and experienced PSM and traction control problems. The car will pull back throttle and engage traction control over 100mph because the shorter rears are spinning too fast. Car was undrivable on track until we changed tires. Same day, back to back runs, different(shorter 24.7") front tire, problem goes away.
FWIW, we have removed the AWD system and it is now 2WD.

The factory stagger in the overall diameter of the tires from front to rear is from 0.6" to 0.9" depending on what brand tires was fitted stock. So if you run a 25.5" diameter front tire, I would suggest running a rear from 26.1"-26.4"

cello

AWD adds another totally different set of issues. My post and comments are for the RWD cars only. Are you saying that the issues persisted with the RWD only set up? If so, OK for you and too bad. I have data that says my car is fine. Hey all use whatever tire you all want. I dont care really and also have no skin in the game...

mdrums

Cello, read his post again...his car is no longer AWD.

cannon1000

I know I would prefer a 305 to the 315 I have now. I am in a 996 Turbo...but it would have to stay the same diameter as the 315 is now so I can run it on my AWD system. It would have to match the 235/40/18 I have on the front's.

I love having more rubber - but it does rub about an inch on the liner...not that big a deal.

333pg333

This is why I asked what OD these proposed 305/35s would be. My guess is that they'd be a bit taller than the 315/30s and potentially exacerbate the issues discussed?

cello

The sentence is "we have removed ... and now its...". The tense used suggests after the fact.

So, he does not say when in time he removed it (before or after the experienced problem), he just says its no longer AWD; hence my question not responded too....

Anyways, my original post was to give a real data point without conjecture for RWD cars only, not to convince anyone...