mooty

wonderful i love ccw and john. though i really dont understand his sense of humor hahaha....

never doubted you on 10.5 anything more cause more push, but the initial sets are very limited in my experimentation. if you can convince john to see if he can stuff 9.5 in front. prolly needs pulling and rolling, but i think make car more lively...

doborder

Orthojoe and I tried to put an 18x 8.5 + 51 offset I think volks racing TE37 Cayman GTS fitment on a GT4 yesterday... No go
Fits on the hub but almost touching the front caliper
We didn't even bother to bolt it on...
Darn...

GAZZ

That must be the closest fitment yet as the best I got was a rub on the caliper.

TAGMotorsports

HRE does make a 19" fitment that works on the GT3 and GT4 without a problem.

There is not a bolt to flip on the GT4. It's not the same issue as the GT3. You can run the 19 it just has to be either very aggressive for an 11 or down size to a 10.5" wide wheel.

The next question is tire size & availability:

Now with the 19's, We you can basically go with a 9" or 9.5" FRONT wheel and run a 265/35/19 - the tire's OD will go down about .5" but the good news is that you have options on tires - The Pirelli Trofeo R, Michelin Cup2's etc.... They are all available in the 265/35/19. Moving to the rear, you run the 295/30/19 which is basically .9" shorter in the rear that factory. The other option is to run the 285/35/19 which is available in the Trofeo R or the Cup2. That size will put you at about .1" shorter OD as factory 20".

To recap - Factory sizes:
20x8.5 - 245/35/20
20x11 - 295/30/20

If you want to go with a 19" Setup - Your options are the following (based off our research form us and our neighbors across the street at HRE Wheels)
19x9 or 19x9.5 - 265/35/19 (.5" shorter OD from factory) (Trofeo R & Cup2 Tires available)
19x10.5 - 285/35/19 (.1" shorter OD from factory) (Trofeo R & Cup2 Tires available)

Now moving on to those who are looking to stick with a 20" option just want something else other than the Michelin, - currently we are working with Pirelli on getting the 295/30/20 Trofeo R's here from Europe - HOWEVER we do not have an ETA. I would say 4-8 weeks at least. (PM ME to get on the wait list for that). We are owned by a large chain of retail tire stores in Southern California so we are trying to muscle our way into getting what you guys need haha

In the meantime - if anyone has any questions at all - feel free to contact me. We can custom make you a set of HRE RC1 series for track use for those who are wanting to go down to 19's without a problem and with the sizes shown there - you might be able to dial back some of the understeer issues as well.

Hope this helps!

mooty

^ very helpful

i have ran mpsc2 255/35/19 & 295/30/19

i think 265/285 may be a bit too frisky in the rear (i am just guessing here). will 265/295 work. i think if that works in terms of diameter relative to OE, this could be THE size.

STALKER99

Good info.
Isn't the front OEM wheel 20x8.5?

Gofishracing

Dimmu- What wheels are those ?

TAGMotorsports

Yes my apologies. Corrected!

TAGMotorsports

Yes however the rear makes it about 1" shorter than OE.... thats why i ran the 285/35/19 which was a hair shorter than OE.

mooty

thanx will have to try 265/35 and 285/35 next season

Mvez

I think this will be the ticket, since Trofeo R and MSCP2 are available in these sizes, and very similar to Nittos for grip (just double the $).

Will be easy to tame the rear with alignment/setup.

ExMB

Those sizes will give you an increased rake, lower front, and may affect your aero. You could compensate lowering the rear suspension or conversely raising the front but not sure how that would then affect your corner balance and/or your alignment.

mooty

^ yes, it will have to be re aligned and corner balanced.
lots of trial and error i am sure

rraustin

Do the 19" wheels for this tire set-up need to vary from the OE offsets of 61 front/50 rear to fit?

TAGMotorsports

The front is going to be a hair more aggressive - the rear will be about the same.