Harvey in FL

Just to add that my C2 with the OEM optional 19" Carrera Sport Wheels also came with
305's.

Alstoy

I keep going back and forth. I do notice a difference in the "look." I also notice a slight difference in handeling and now prefer the 295s. I'm waiting to get to the point where my fronts and backs are all out together to replace with 18" C3s.

Dave07997S

I did notice a tad more understeer due to the fact the rears do seem to stick a little better. I want to do a 19X8.5 or 9" wide rim with a 245 on the front along with the 305's in the rear.

Dave

Edgy01

I always suggest that owners stick to what they found on their cars from the factory. I specifically ordered the Carrera Sports because of their sizes--8.5 and 11.5 in back. They are the widest wheels ever available for a 911 since 1965. You will discover that more is good on a 911. But for an 11 inch rear wheel perhaps a 295 is right on the money.

Mike in CA

That would be a good combo. As you point, out the big sticky tires on the rear do contribute to understeer. That's why for my autoX tires I went with 235's front and 295's rear even though I have 235's and 305's for the street . 245's in front weren't an option for me with the wheels I'm using for the track so 235's and 295's worked out best.

KeninBlaine

What are the factory tire sizes on GT3s?

Nugget

997.1 GT3, 997.1 GT3 RS, and 997.2 GT3 is 235 front, 305 rear.
997.2 GT3 RS is 245 front, 325 rear.

KeninBlaine

Thanks Nugget. So why do so many here think that 235 fronts with 305 rears is a problem if that is the way the GT3s are equipped, as well as any Porsche that is ordered with Carrera Sport wheels (which have wider rims)?

Mike in CA

My 2 cents, I don't know that it's a problem, but there's no question that all else being equal, more tire at the rear relative to the front means more rear grip and increased understeer. With the GT3, suspension tuning can mitigate this, and with their extra power, more rear grip translates to getting out of corners faster, so its a win. On the Carrera's like mine with the Carrera sport wheels, I'm bound to have a bit more undertsteer because of the bigger rear tire but it's probably offset somewhat by the wider front wheels/track and besides it wouldn't be noticeable at anything less than 10/10ths anyway. So it becomes a marketing ploy.....those steamroller rear tires do look cool! For autoX, I'm looking for every edge, so a little less rear grip is to my advantage turning into a corner, so I went with 295's.

KeninBlaine

Seems like a plausible explanation. I have to admit, the couple of times I autocrossed my Targa last year, with 235 fronts and 305 rears, I had a terrible time making my front tires stick, even with AWD. My instructors and I adjusted pressures etc. but it never seemed to solve the problem. I just thought it was the crappy (and worn) Pirellis, but perhaps it was partly due to the fat rear tires. Since I have a spare set of lobster claws now, I think I'll put on 235 and 295 tires and swap them with my other wheels when I attend autocross events in my C2S cab.