mobonic

What is the widest FRONT tire you can fit on a 997 NB?

Can a 265 front fit without rubbing?

Will rolling the fenders help them fit ok?

Its for track use.

I run -2.6º FRONT CAMBER

Edgy01

NB or WB--both are the same up front.

Why don't you try it and report back? The other bigger factor is the wheel width.

On Pole

Stock fenders, 9" wheel -1.7deg camber 255/45-18 R6 is what I use

tcsracing1

i have 265 on stock 19" wheels up front. no problems. (a-la NJGT)
(i did however raise the suspension for a rally which caused a rubbing at full crank with the alignment i spec'd.)
but at proper height you should have no problem.

340Elise

I run 255's on 18" x 9" wheels. I have been wanting to try a 265 and I doubt it would be an issue. However, wheel width is important and I plan on going with a 9.5" wide CCW on the front and then run with 265 tires. The rear will probably stay at 12", but I may do a 12.5" if I decide I want to run a 325 (which certainly will fit a 12" rim, but is not ideal).

Although a 265 may fit on the stock 8.5" wheel, I do not think it is a good idea, and in the end is really a waste of a wider more expensive tire. Tire specs such as tread width and especially section width will change for a tire based on the width of the rim it is mounted on. You can get more performance (stick) from the exact same tire by simply increasing the width of the rim (within spec of course; too wide is not good either). This would be true for a tire that is really mounted on too narrow of a rim such as a 265 on an 8.5" rim. I say that the 265 is a waste because the rim width is limiting its full potential. Even a 255 on a 8.5" rim is not ideal and ends up being pinched without being able to fully expand and sit squarely on the rim.

A good example is GMG Racings WC GT3 setup. They actually run a 10.5" wide BBS wheel in the front and use a 275 tire. 10.5" is really damn wide and makes you wonder why they went with such an extreme width. It is because that size allows that 275 tire to sit square and gives a nice flat, complete contact patch for the full width the tire has to offer. A 275 tire is supposed to be 275 mm wide or 27.5 cm. 27.5 cm is 10.8 inches. Makes perfect sense to me that they are using a 10.5" rim.

Why does the 997 GT3 have a 12" wide rear wheel for a 305 tire while the turbo and C4S have an 11" wide wheel for the same width tire? Or how about the new GT3 RS? All they did is go from a 235 to a 245 tire and right away they went with a 9" rim. A 245 easily fits on the 8.5", but the 9" makes it better and is really the right way to do it.

To help you with the fitment of a wider front wheel/tire, you may want to look at the new front fender extensions from the new RS. I already have a call in to Sunset Porsche to let me know as soon as they have a part number and can order these. They should fit on the 997.1 cars with the only issue being the portion that sits on the front bumper. I'm confident that my body shop will be able to get these to fit nicely with minor modifications for the bumper portion. I do realize that the fender still needs to be looked at and possibly modifed. If the car sits low enough and the wheel/tire is too far out, then the top inside edge of the fender will hit the tire, especially under hard cornering. I want to see exactly what Porsche did with the RS front fenders to accomodate the 9" wheels. Did they simply tack on those extensions, or did they also modify the fender lip?

You could go with the wider CF fenders that many shops carry such as the ones from GMG, but that gets expensive. I like my RS idea better (financially) if it works as I envision it.

btw, a 9" front wheel works for our cars without fender mods, but anything over that and something needs to be done to the fenders if you want to do it the right way.

Anyway, sorry for the long post; probably more info than you cared about.

PogueMoHone

If the new RS wheel is 12", you have some more explaining to do, where you say a 12"/325 is not ideal. The rear tire is a 325! Then you go on to complement Porsche on the upfront choices.

Is it possible the rear wheel is wider than 12", or that they could get the front right and screw up the rear?

You have PM since I have some photos I can send you of the front section of the RS.

mobonic

Thanks Stephen... very informative post.

I have access to some great deals on Toyo R888 but they are:

265/305

and im worried they will not work on my car... i guess i have to try and see for myself.

340Elise

How about the 255's? I get the 255's for $230 and the 305 or 315 for $305/$300. I believe you are using 18's?

340Elise

You caught that; I can't believe someone actually read one of my essays! I did want to address that but did not want to double or triple the length of my post.

The new RS comes with a 12" rear. Also, the 997 GT2 has a 12" rear with a 325.

Just because it may not be ideal, does not mean that it will not work or provide improvement. The 12" rear may be ideal for a 305, but it is really pushing it. The recommended range for the 305's that they put on the GT3 (MPSC and Corsa's) I believe is up to 11.5" from tire manufacturer, but obviously the 12" works and is equivalent to 305 mm. So if the 12" rear is the very upper bound of the 305, then a 315 and even 325 should work just fine even if a 12.5" rim would be better for the 325.

I was mostly referring to combinations that technically work (the tire will fit on the rim), but are really far off from ideal such as a 265 tire (10.4") on the stock 8.5" rim.

Look at it this way: stock MK1 997 GT3/RS and MK2 GT3 sizes are 8.5" rim in the front with a 235 tire and 12" rim in the rear with a 305 tire. If you convert the 235 mm tire to inches you get 9.25" and the 305 is 12". So the front width of 8.5" is certainly acceptable, but is almost one inch from ideal while the rear is right at the upper edge with plenty of room to go up a size or two. With the RS having a 245 in the front, then that would be at 9.6" and it makes sense to go up a half an inch. The 325 comes out to 12.8". So with the RS going with a 9" front and 245 and 12" rear and 325, the front rim is only 0.6" from "ideal" and the rear 0.8" from "ideal". Seems like a better balance of proper fit for tires than what they have on the MK1 GT3/RS and MK2 GT3. I put "ideal" in quotes (there I go again) because I'm not sure that having the rim width exactly the same as that of the tires mm width as ideal. I am only saying that it is good for these two measurements to be close to allow the tire to sit properly on the rim and sit squarly for its intended width. Maybe it is ideal for the rim to be a half or a quarter inch narrower to make sure there is enough pinch on the tire so it does not spin on the rim, but it does not pinch it so much that the tire cannot keep its full, flat contact patch.

Also, with the new RS going to a 245 AND a 9" front rim, the affect on front grip is greater than one might think and it should really help with turn in and reducing understeer. However, the 325 in the rear will probably cancel out that tendency toward more oversteer and bring back approximately the same balance as the MK1 RS but with overall grip levels being higher. This is with all things being equal on alignments, tire pressure, swaybar settings, dampers/springs.

One other thing to consider is the aspect ratio of a tire and how this allows the tire to be pinched on a more narrow rim. If you look at the 18" Toyo R888 in the 305/35 size, the upper recommended rim width is 12"; however, the 18" 315/30 Toyo R888 has an upper recommendation of 11.5". The lower sidewall allows less sideways travel of the bead of the tire than the higher sidewall.