wbrownie

You do not have 12mm more track than stock.

You have 14mm less. (2 x 7mm)

A rim that is 1 inch less width (25.4MM) with only 6 MM more offset will not give you wider track.

Do it the old fashioned way, take a tape measure with each set of wheels and measure.

RonCT

How is that possible given the offsets. For example, if I had an 11" wheel with ET 65 and an 11" wheel with ET 62, which would give more track? The ET62 would give 3mm per side more track for a total of 6mm overall. Take the same wheel and add 1/2" of material to make it a 12" wheel. The center of the wheel stays in the same place. The contact patch of the tire centers on the wheel.

997gt3north

Ron

I think this may be a definition thing. If by track we are referring to the measurement from outside rim edge to outside rim edge then even though your 11 inch rims are a few more mm offset this is not enough to overcome the additional 12.7 mm per side that the wider 12 inch wheels provide. That said, you will not know the actual track unless you messsure it because you will not know how a tire sits on a RIMM untill you messsure it
Paul

RonCT

I think you nailed it on the head. I consider track to be tire placement while others may consider it outside edge of the wheels. I figure the contact patch is constant whether you stretch the tires onto 12s or leave them comfortably on 11s.

Just eyeballing it, it's pretty easy to see that on the 11" rim, the 305 sits pretty nicely and has maybe 1/4" of distance between the outside edge of the rim and the melted rubber / contact patch. However, on the OEM wheels, the 305 is stretched quite a bit and it looks like there's about 3/4" from the outside edge of the rim to the contact patch. Based on all of the math, that would clearly put the contact patch track wider on the 11s with the lesser offset. I don't have the time to take actual measurements (have to change rear wheels), but I'm thinking that my theory is right on here.

340Elise

I think we should just compromise on an 11.5" rear width.

RonCT

An excellent suggestion my friend - maybe now this thread will just fade away until somebody in the future searches with the question "I traded my 997S for a GT3 and I'm wondering if my 11" Volks will work..."

mdrums

Nope not gonna let it die...hahahaha...anyway RonCT I was thinking about you on my flight back home when I was reading the write up on the GMG mod'ed 2008 GT3 in this months Excellence magazine. You should check it out and read about the BBS wheel sizes they used.

340Elise

I already mentioned that; doesn't anybody read my posts!

Anyway, he is right. The front is a 10.5" and the rear a 12". They are using a 265 front and 325 rear. I thought that 10.5" was way too wide and a misprint, but it is not and I'm guessing they are using the same logic as Porsche for the really wide rear wheel. Although 10.5" is still super wide for the front. And yes they have the wider CF front fenders to fit these wheels.

The GMG WC GT3 is just plain impressive!!! It is much closer to what the RS should be IMHO.

Yargk

This statement seems just wrong or at least misleading. A contact patch is a function of tire, rim, and weight of the car (I can't think of anything else, well alignment of course and aero if you're talking dynamics at speed). It has nothing to do with the center of the rim (unless you're talking corner dynamics in which track width may affect weight transfer). A 12 inch rim will give you a slightly wider contact patch than an 11 inch rim. What you're trying to say is that the distance between the left and right (smaller) contact patches will be greater with the offset of your 11 inch rims. This is track.

That being said, 11 inch is fine, cups run it, don't worry.

Yargk

340, we are just too like minded when it comes to gt3s. Now please do the lightweight carpet kit, sunroof delete, motons, gmg front fenders, 10x18 front wheels with 265/35, 10X12 rear wheels with 315/30, cup lip and cup wing, RSR suspension goodies, etc., enjoy the car that's lighter and faster than an RS and still perfectly streetable for a couple years and then sell it to me at a fraction of the cost.

Chris C.

Well, I've split the difference with the RS98 in 11.5" sizes myself!

Good info guys, thanks for the education

mdrums

Sorry must have missed your post. That happens to me a lot too! Any I thought GMG was running the smaller size tires (305 on a 12") during the review and that they were going to go to the wider tires and fenders.

Anyway, you can't judge track by just the offset of a rim.

340Elise

They were running the 305 during the review, and I forget the front size. I was just pointing out where the car is now and that the front rim width is just crazy wide. They are using a 265 front, but I believe in the article they mentioned that it could accomadate a 275 front (that is obvious if it is a 10.5" front). I'm sure the front rim could fit a 295 no problem, but then you run into the rubbing issues, so I guess the 275 is based on that restriction.

Btw, reading that article is how I got my PCCB's. They mentioned that the GT3 they used to build this WC car had the PCCB's. So I decided to give them a call to see if they were still laying around and for sale. Sure enough they were!

Now if I could just finish with the installation of these brakes I would be even happier!

340Elise

I am working on it my friend! Since I have the suspension taken apart in the front of the car, I figured that I might as well go with these GMG upgrades in the mean time:

Bumpsteer kit for front and back
Rear dog bone kit
Thrust bushing kit (front non-adjustable and rear adjustable)
Toe steer kit
Inner a-arm kit
Adjustable rear control A-arms (GT3 already has front adjustable)
GMG latest sway bar kit for the GT3

I want to wait on the Motons with the Eibach ERS Racing Springs for now, they will be the next upgrade depending on how the car feels with the stock PASM's.
The Grand Am Rolex uprights with revised pick up points??? That seems a bit hard-core for now and it can be added later.

The wheels I am still deciding on between the Dymags, BBS E88, and Champion R-98's (is that the correct model designation?) I don't think I will do the fenders. I would like a 265 front with a 325 rear, but a 255 front and 315 rear seems just fine with 18" wheels, or 245 with 305 rear with the 19's.

As for the wing, I already have the RS wing and Cup car front splitter. For interior I have the 996 GT3 seats in cloth (much better and a couple lbs lighter per seat than the leather ones IMHO).

I also have the SharkWerks center muffler delete and the GMG version sitting around to be installed just to see the sound differnce. I love the SharkWerks one, but I like to play with exhausts.

So what does a fraction of the cost mean? 95/100th is a fraction!

mdrums

good idea on the PCCB's...you acted fast! A guy I track with has a 2002 turbo with CCW wheels and he is running 265's on the front just fine. Also the blue wheels in your avitar look like my CCW C14 wheels but painted blue. Is that what they are? Are they powder coated and how did you get a center cap to work with the C14's?