ir_fuel

For those of you using 18" wheels, what tyre sizes are you using?

Thanks

rmag

Hoosier R6
Front 255/35/18
Rear 335/30/18

ir_fuel

isnt that gigantic?

Why so wide if stock they are 235 / 305 ?

rmag

Oops, thats for my RS.
On '07GT3 ran R6
Front 245/35/18
Rear 315/30/18

Polarporsche

I just ordered a set to go with my Forgeline CL wheels, first time for R6's, I ran NT01, MPSC, & R888's on my 996 GT3.

Hossier R6
Front 245/35/18
Rear 315/30/18

mkozink

2007 997.1 GT3 RS
Toyo R888
255/35R18 on 18" x 9" CCW C10 wheels
315/30R18 on 18" x 12" CCW C10 wheels

Only other mod to suspension is TPC adjustable rear toe links and track alignment.

The grip is prodigious.

lawjdc

+1 for a 2007 GT3 or RS

mdrums

Hummmintesting specs....stock size is 235-35-19 and 305-30-19 and the guys I run with seem to be mostly using 245-40-18 and 305-35-18 since this keeps the overal diameter right at the same as the stock 19's.

I've seen a few run the 255-35-18 and 315-30-18 to lower the car and gear it down for more acelleration.

I've always been told that when going to an 18" from 19" on the Carrera S and GT3 that I need to keep the overal diameter the same so that ABS and PSM do not freak out.

AllanJ

I don't think that's the case. It isn't so much the overall diameter that's the issue, it's the comparison of front and rear diameters that the computer will care about. It's going to expect a pre-programmed ratio and will use that value to determine if the fronts are sliding compared to the rears, etc.

But keeping close to stock diameters is easy and doesn't involve much math.

fyi, I worked out the math and the 255/35/18 + 315/30/18 combo should be just fine. It's just over 1% different front/rear ratio from oem. I think the computer is fine with up to 5% difference.

Cheers,

ir_fuel

So you all go much wider in 18 compared to the 19. Any specific reason? So I guess going to 18 doesn't mean cheaper tyres.

aero997c2s

Similar tires in 19's would cost a bit more. I found a site where a 305 R888 in 19" is only 40 dollars more expensive than the 18". MPSC's probably cost a lot more in 19" than 18"

Nugget

I run 245/35ZR18 and 315/30ZR18. I've never been motivated to try anything wider than that, but I've never tried wider either so maybe I just don't know what I'm missing. I've never had any problems with ABS as a consequence of the non-stock tire sizes.

While the Hoosiers aren't cheap, I think that overall I save money because my expensive street tires on my 19" wheels last forever now that I'm not scrubbing them up on the track all the time.

AllanJ

...and you shouldn't have any problems. I did the math and that front/rear ratio is almost perfectly matched to oem sizing.

Cheers,

obsessedone

I have 18" 245/35 & 315/30 Hoosiers on my S and love them - no issues to date with ABS, I do usually run with PSM off as it tends to cut power & pulse brakes when agressively exiting tight corners. I think I can feel a bit of extra acceleration from the slightly changed ratio but it may be my imagination. I do know I can compete better against the same cars with the 18s and these tires than I can with the 19s - tried both same days. My 19 wheels are now for sale.

Fast Fred

Are you sure you can fit 18" on a 997.2 GT3 ?