I'm thinking of getting new tires for my 19" P40s I love my 18" Nt01 s but they don't make them in 19" so I'm looking at their sister co. Toyo R888 but they only offer them in 235/35/19 and 305/30/19 will this rolling diameter f-up my diffs anyone using this combo?

 

I am running the P40's 19" with the stock 997TT Michelin PS2's in the sizes you listed with no problems to date. Again I believe this is what Porsche puts on the stock 19's on all 997TT's...so I don't think they will F up your diffs.

 

There was a discussion here about this but I can't find it now, you have to be within certain size difference for your diffs to operate right without damaging them. I am also trying to figure out what would be the biggest size I can go without any issues for the new HRE 19" wheels I just bought. 9X19 Fronts and 12X19 Rears and I still cannot figure out tire sizes for them. So far I was told 235/35/19 Fronts and 315/25/19 in the back. But some people I talked said I could go bigger. I am really confused.

 

I would say no bigger than 235/35/19 Fronts and 315/25/19 in the back.

 

The 315/25/19 tire comes in a full inch shorter than the 305/30/19 tire.
Personally I would not do that. I know of one diff disaster down here in So. Florida and that's one too many. The 315/25/19 has a rolling diameter of 25.2" and the 305/30/19 rolling diameter is 26.2".
The 235/35/19/and 305/30/19 are stock dimensions for the 997TT and the GT3/RS's.
Also the new GT2 comes with 325/30/19 if not mistaken. That has a rolling diameter of 26.68". A better set up I believe.
I do not think they make a 315/30/19?

Call Ben at Wheels Botique here in Miami. He can give you more detail regarding the tire release and manufacturer.

Good luck
Ranger

 

check on tirerack.com

 

I think that the GT2 rear tire size does not matter as the GT2 is rear wheel drive. Here is what I have found for you:

235/35ZR19 OD 25.47
305/30ZR19 OD 26.25
315/25ZR19 OD 25.20

These are the sizes I would stay with after surfing the web.
I hope this helps!

 

This guy selling on ebay claims for maximum fitment it is OK to use 255/30/19 in the front, which I am not sure if it would be a good idea or not. After doing some math I don't even know if this is a right math to calculate it but got me even more confused.

OEM
Front: 225/40/18 (225X40% = 90)
Rear : 295/30/18 (295X30% = 88.5)
Difference: 1.5 Safe Zone

MOD
Front: 235/35/19 (235X35% = 82.25)
Rear : 315/25/19 (315X25% = 78.75)
Difference: 3.5
This is more than double the difference compare to OEM fitment. Plus my new HRE's are size 9X19 and 12X19 which is wider than the usual . The question is would these size tires fit and look OK on my wheels. Any input is appriciated, thanks...

http://cgi.ebay.com/ebaymotors/Parts....c0.m245.l1318

 

First, unless you are actually measuring the diameters, this is all theoretical. That being said here are the numbers I have:
235/35-19 3.2in 12.7in 25.5in 80.0in 792 0.0%
315/25-19 3.1in 12.6in 25.2in 79.2in 800 -1.1%
305/30-19 3.6in 13.1in 26.2in 82.3in 770 2.9%

I run 235/35-19F and 315/25-19R Yokos with no problems.

 

common size and definitely works. I had the Pirelli PZero in that size on my 996TT for a while. The R888 is an EXCELLENT tire. I can tell you that the Toyo are cut differently then say a Michelin... So the fronts might be a bit more stretched looking. That is my experience from Toyo T1R. Here is my Toyo Catalog.