dbanazek

We are having a discussion about using 18" wheels in SCCA GT2 on the gt-racing.com website. I was wondering what sort of slicks you cup car guys are using, or anyone using 10 & 12 x18" wheels or so is using.

Where do you get them, what sizes, how much, how liong do they last?

We are currently stuck with 16" wheels and the goodyear 16" radials are about $450 a copy. It seems we could save money in the long run using an 18" slick.

ngoldrich

My wheels - 11x18 & 13.5x18 on my 993 GT2 (twin turbo).

I normally run Dunlop slicks but also tested with Pirellis.

With as hard as I push the car, I only get 2 heat cycles out of the Dunlops. I am running a locked rear spool which does not help the fronts at all. Actually I have to drive it like my shifter kart.

But for what its worth, here is a sample :

Session #1 - stickers - drives like a dream, I smile the whole way around the track - fastest they will ever be from the first lap.

Session #2 - takes a 1.5 laps to warm them, then they drive pretty good. About .6 serconds slower than the first session

Session #3 - takes 3 laps to warm them. About 1.5 seconds slower. No much fun driving since the limit is much lower

Session #4 - car is undrivable. Just wont turn in. Not even worth going out...

I am running medium soft fronts and medium rears. Tire pressures and temps are perfect.

After 3 sessions, my rears are still fine, the fronts are gone. So I will start running 2 or 3 sets of fronts to every rear set.

I will also probably get rid of the spool which will help get rid of the understeer.

Dunlops are expensive around 1650 per set... Pirellis around 1250, Michelin around 1350, Yoks around 1300...

The pirellis were no where near as good as the dunlops on my initial tests. But I will try more compound tests to see if I can make them handle as well as the dunlops since they cost much less...

Norm

carreracup21

Norm,
I'm sure that rocket must be an E-ticket ride, but man that must be an expensive weekend of racing with 2 or 3 sets of tires. Yikes.

fatbillybob

Im with carreracup21...yikes! Maybe thats why I'm so slow. I use used 1 heat cycle slicks from the guys who sell on the back of GRM. Contrast $400 busks a tire with $80 bucks a tire! In fact I only went out maybe 4 times last year and I just put on new old ones. I think the cornering limits on the used slicks are probably better than DOT R or streets so what the heck. For what is is worth Pirelli stopped the used market. You can still get dunlops and goodyears but not pirellis. It seems Pirelli want to sell more tires and they threaten to take away tire distributorship from anyone who sells on the secondary market. That means to get them you gotta know a clubracer who uses once to qualify and dumps the set to the next set for the race and buy direct. I love the pirellis over the DOT's. I happen to have an extra set of 1 heat cycle 295 680 18 Pirelli slicks if anyone needs them.

ngoldrich

carerracup21, fatbillybob,

I agree. The price and longevity is ridiculous. That is why I am testing others like Pirelli to see if I can find a setup that is almost as fun to drive, is more cost effective, and lasts serveral more sessions. I am just really starting to test others now. The hard part is I dont want to test them at a race...

Norm

Glen

Norm, You will find the Michelin's last much better when pushing as hard as You do. They stay more consistent is the best way I know to describe them with them perhaps not having quite as much stick initially. I use the Yokes but will spend up for the Michelins a couple of times this coming year depending...

Glen

BTW, I mean the EURO Michelins...Dunno if You can get those in the sizes You need though.

ngoldrich

Glen,

Once I get done with my Pirelli testing, I think Michelin will be next on the list. I will try going one compound softer (D7 front/D6 rear - currently d6 front/d5 rear )on the Pirelli first and see if 1 size larger in the front will fit and 280 front instead of the 265 I currently have.

If I can get rid of the understeer with that setup, then I may be okay. But I still would like to get more consist longevity...

I think I will then try Michelin...

Thanks,Norm

ngoldrich

Glen, where do you get Euro Michelins ? I was thinking about getting Michelins from subesports.com

Norm

Stuttgart

you're running D6's! That might be why you're eating tires. What kind of temps are you seeing? Have you tried running D3/D2 front/rear?

ngoldrich

Phill,

For my car, Bob Woodman actually suggested I run D7 front D6 rear for VIR.

My tire temps and pressures are perfect.

The tire temps and pressures were also perfect on my Dunlops.

Norm

kary993

Seems to me that if you want to eliminate your understeering tendencies and want some longevity to your tires you might do something like a D5 front and D3 rear. You can of course play with the differnetial between the compounds from front to rear to find the optimal pair. Running extremely soft tires as you are is not going to give you any longevity as I am sure you are aware. I normally run a D5 front and D4 rear or a D6 front and a D5 rear. This works well and eliminates understeer and allows for some longevity depending upon the compound pair I choose.

ngoldrich

Kary,

Interesting idea which would probably get a good balance. Unfortunately even the D6's up front have such bad understeer in my setup that the car is no fun to drive and turns in extremely poorly. The fron braking grip is not good either with the D6's...

Data acq shows I am pulling almost .5 less G's and 2 secs a lap slower than my Dunlops. So going harder would indeed make the tires probably last longer, but the car would not even be drivable.

Although taking that same line of thought, it might work to run D7 front d5 rear. I was planning on D7/D6, but your idea of a wider variation may indeed balance the car better.

One thing I did not mention is that my rears last fine. So I may stay with Dunlops and just run 2 or 3 sets of fronts to each set of rears. I am very easy on the throttle so I do not light up the rear tires much.

It is amplifying the problem having a locked rear spool. I have to drive the car like my shifter kart.
But I think I will be putting in a Paul Guard clutch type limited slip. That should help tremendously with the low speed understeer.

Thanks for the suggestion.

Norm

kary993

Norm, I think the bigger compound spread will help though with a locked rear end that is hard. I have a Guard LSD and really like it, though it has increased my understaeer I was able to dial it out.

Good luck and keep us posted on your next tests.

ngoldrich

Kary,

You mention the Guard LSD increased you understeer. Why, what did you have before ?

Any type of LSD, I imagine and hope will tremendously reduce mine since I have the locker.

Thanks for all the info.

Norm