On my 996Turbo i had 265's up front. I had to do my homework on offset of wheels. IF Jon can fit 275's up front on a 996, 997gt3 owners should be able to do so as well. I currently run 245's on the gt3 however it has not seen much track duty. If i were to start getting heavy back into it- i would do the due diligence to fit 265's + - makes a world of difference like Jon has stated.
My setup was 265/s 315's on my 996t. Hint of oversteer - which i liked.

 

I have 275 front and 305 rear 19s for my street wheels and having the big tire up front has felt a ton better.

I'm looking to get some 18" track wheels and should be able to do the 275/335 setup no problem being I have the cup fenders and flares on my 7GT3. Excited to try that setup out. Fwiw the cup ran 18x10 fronts.

 

i ran 10s in a 996t w stock fenders. No rub. You could easily run 295s wi the correct offset/ camber if you have cup .2 fenders

 

What I'd be interested to know is at what point does grip with increased tire width start to impact straight line speed with all the tire scrub.

Does the grip of 295 fronts provide that much more grip than 275s to warrant the effect it has on straight line speed.

 

Just switched to the 245/305 NT01 setup from 245/315 Kumho V710 (and they ran wide). Definitely wish I had a bit more tire under there but car feels pretty good.

Now I need to roll the fenders further so I can go big on the next set......

 

The 245/315 Kumho V710s are great tires. I've run 4 sets of them over the last couple of years. They are about 1 second quicker than the 245/305 NT01s. The only drawback was that they did not last very long. I always got about 7-8 sessions out of them before they were done. Miles/$ just was not there.

To give you an idea, here are the 275/335 NT01s in action. I was able to turn a lap 1/2 sec quicker on them than my best time on V710s.

 

damn, what a cool track.

 

HPR is a great track. +300' of elevation change per lap, lots of off camber and blind turns, very challenging.

 

V710 is an autocross compound designed to get up to temp quickly but not last long, similar to Hoosier A6/A7

 

Not to mention steering feel and the ability to get the tire up to temp fast enough.

 

I didn't find the V710 come up to temp any quicker than NT01s for example. To the contrary actually. The literature doesn't necessarily label it as specifically an autocross compound. I did one autocross with the V710s and I thought they were horrible as I could not get any heat into them. They were super slick.

http://www.kumhousa.com/tire/categor...7-B13BC6B9E6B2