KenW

Well, now everything is becoming clear as mud. Within a month I shall be buying 18" wheels and track tires for my recently acquired never tracked 996 GT3. The car is to be primarily a track car, driven to and from the track. The alignment is now "Kussmaul", the GT3 seats and the Techquipment bar etc. are in, the suspension is STOCK and the car has low milage. I want to go as quick as possible without extreme rubbing, there can however be the occasional acceptable "little" rub. Can you guys help? Is there a general consensus? Can there be a general consensus? Please consider that Mosport, Calabogie, and Le Circuit Mont Tremblant will be the main tracks, primarily Le Circuit. I WAS thinking 9x18 +44 mm offset and 11x18 +64 mm offset with MPSC 235/295 combo. NOW after all of the above, I'm leaning towards CCW or Fikse 9.5 and 11, MPSC 235/305 combo. Or, 11.5 rears? Doggonnit ??
So... please help. Can we nail it down? The tire sizes I can move around, the wheels have to be correct. Many Thanks!

NJ-GT

996 and 997 GT3 Cup sizes: 240mm/270mm (slicks). Rear tires 12.5% wider than front tires.

Using these ratios, we can have the street car with:

- 265/295 (I ran this on MPSC 3 years ago, loved it)
- 275/315
- 295/335

The stock 235/295 sizes are the ideal sizes for average drivers. Porsche does this to prevent drivers from crashing on their first attempt to go fast. All manufacturers set the cars with understeer to make them safer on the road.

When people insist on running 235/295 MPSC as the ideal track tire, I can't argue. If they feel comfortable with plenty of push, is up to them.

My 285/335 setup is neutral with a little bit of tendency to oversteer only on heavy lift. I like it a lot.

KenW

Hello NJ-GT and thanks.

You mention "I've 10"/12" C14"
AND you suggest "I would go with 9/11.5 and 245/255/265 fronts and 305/315 rear"

Later you mention ""For stock sizes r-comp tires, I would use 9"/11" CCW wheels on 245/305 tires, with the sway bars in the stock positions. If using 295 at the rear, set that rear sway one hole softer."

Should I in your opinion be ordering (for 235-245 / 295-305-315 combos) 9x18 and 11x18 or, 9.5 and 11.5. Keeping in consideration your 10"/12" C14s, that I do not want serious rubbing, and I have a lot of experience and I ... push.

auto-xr

Did a search and found more people going back and forth on this wider tire debate.

http://www.eng-tips.com/viewthread.c...=102250&page=2

NJ-GT

I run 10"/12" with 285/335 on my GT3, I don't recommend these sizes because other than my car, I have not seen anybody else with a GT3 successfully running them. These sizes don't work on a 996 GT3, they work on mine because I made it work through some tricks: rolled fenders, no fender liners, narrower springs, more negative camber, no camber shims and custom camber plates.

For people that want to run stock sizes or close to stock sizes, 9"/11" wheels and 245/305 is the common ticket. Push, yeah, front wheels lock during braking, yeah.

If you want to run wider tires without having to roll fenders, or being concerned about rubbing, then 9.5"/11.5" on 265/315 is a good combination. Once you get to 12" the 315/30 rubs, but the 305/30 doesn't.

Personally, I don't have a problem rolling fenders. It is just so easy, and you free up 20mm wider sizes not doing anything else. With rolled fenders, you can run 9.5"/12" wheels and 265/315,

Porsche needed to make the GT3 RSR faster for last season due to the F430, they added 200 lbs and changed from 9"/11" and 10.5"/10.5" wheels to 11" and 13" so they could run 270mm/310mm slicks.

karlooz

you didn't have to do the RSR trick (swapping the front control arms left to right then using the front eccentric mounting point) to get the 10s to work? i hear it will give you much more room between the radiator mount and the tire at full lock but it also brings your caster to ~3.5˚. i may try it out when i go to 10s up front.

mjb

Whoa, caster around 3.5deg?? Sure that's not a typo? Should be around 8.5deg or so I think.

karlooz

not a typo 3.5. it'll be fast steering that's for sure. 8.5 is stock for a STREET car. i am talking about a RACE car.

KenW

"For people that want to run stock sizes or close to stock sizes, 9"/11" wheels and 245/305 is the common ticket. Push, yeah, front wheels lock during braking, yeah.
If you want to run wider tires without having to roll fenders, or being concerned about rubbing, then 9.5"/11.5" on 265/315 is a good combination."

OK, if I want maximum grip, quicker lap times with minimum fuss, ~ standard expense, more tire size options, it's 9.5"/11.5".
Uh, right? I think and hope so... thanks.