jtg077

I just bought a used set of 18" Carrera III 5 spoke wheels to use with track tires for my 2007 Carrera S.



These (carrera III) wheels are

Front: 18" x 8"

Rear: 18" x 10"

Stock Carrera S:

Front: 19" x 8"

Rear: 19" x 11"

I want to buy the Toyo Proxes R888 in these sizes.

Front: 235/40ZR18 Overall Diameter 25.5

Rear: 295/30ZR18 Overall Diameter 25.1

Will this setup be ok with the overall diameter being different than stock wheels/tires? Will this effect ABS, Traction, etc.? If this will not work, what are my options?

Mike in CA

I'm using 18" Carrera IV wheels for autox in nearly the same dimension as yours (rears are 1/2" wider) with Michelin Sport Cups that are the exact size as the Toyos you are considering. Zero issues with any of the electronic nanny systems. The slightly smaller diameter effectively gives you a shorter gear ratio for a little more pull out of the corners at the expense of a bit of top end (irrelevant for autox). I've run them for almost two seasons now, and as I said, no problems.

mdrums

Those are darn skinny wheels and tires for real track work. For 18's on a 2006, 2007 and 2009 Carrera S I used along with many others I track with

9x18 fronts
12x18 rear

Tires sizes were either
255/35/18 front
315/30/18 rear

OR

245/40/18 front
305/35/18 rear

acadian_dad

I used those same wheels on my 997S Cab for track tires - I used Much PS cups. They were fine. No issues with PSM or ABS.

I'm sure wider would be better but they were fine for DE's

deijmaster

Why in the world would you want to put 18 inch tires on a carrera S when it comes default and is geared with 19....? I know cost is always an "issue" but this a Porsche, not a Golf...

jtg077

Well I wanted 18" tires because more tires are available in 18" instead of 19" and they are also cheaper. I see a lot of Carrera, carrera S's, and GT3's with 18" wheels/tires.

My main conern is it ok to have slightly bigger overall diameter on the rear tires? It looks like I have not choice. I cannot go any wider than 295 on my 10" rear wheels. Also, Michelin Sport Cups, Toyo R888, and Yokohama A048 all only come in these sizes I listed below.

What should I go with?

Front: 235/40ZR18 Overall Diameter 25.5
Rear: 295/30ZR18 Overall Diameter 25.1

acadian_dad

18's have more choices for track work and are cheaper. Those are the sizes that I used (sport cups) and were fine - no PSM or ABS issues etc.

You get more grunt (lower effective gearing with the smaller rear wheel) - but may change where you shift at your track if you are used to 19s.

Mike in CA

Many people who track their cars prefer 18's just for that purpose. Lighter weight, better tire availability, etc.

garage1

18" for track
19" for street

seems like the mainstream approach for all of the obvious reasons suggested....

if only we could still find 305/18s in RA1 or for that matter anything other and 888s.

C'mon Toyo - satisfy a market NEED!

Alan C.

From what I have read I wouldn't want a larger diameter tire in front. Some people have had problems with larger fronts.

Mike in CA

What kind of problems?