Jean

New 19" Forgeline track wheels with my specified offset. Bought for the GT2RS, tried them on the turbo and they fit perfectly also, quite surprising that the same offset works the same on both cars. Last Time attack race this coming week-end for the turbo and then it retires most likely

Randyc151

They look great on the Turbo! What tires are those, and are you going to keep running them on the 2RS? I'm still working on my choices right now.

Pdtp#16

That's awesome. With the turbo narrower axle width it probably makes the difference to fit within the stock fenders albeit of the wider wheels and different offsets.

Are you running the 2RS? would love to see some data comparison on the two while on track. Curios to see how differently each behaves with actual data.

Good luck

Jean

Yes I got them for the RS, I will be using the same tires for it. These are Pirelli 275/675 and 315/705.

Will need to test the front caliper to wheel clearance on the track, I tested on the road and they’re ok.

Jean

Pdtp these wheels are about 3% wider front track which was my target for the RS, that’s close to Clubsport specs.

I haven’t run the RS on track yet, I am getting it sorted. I will definitely compare logs and share once I get a chance..

onfireTTS

Good luck with that AWESOME project. I'm envious of your GT2RS ! Incredible car !

Jean

Thanks Onfire, I have a soft spot for the Turbo after all the work I did on it, it’s just perfect and definitely on another league in terms of handling and power vs. a stock RS.

pepinozaur

What a car! I am in love with your black Gt2RS on slicks, doing the same setup on my black 720S track edition. Will do Finspeeds in the end 10"/12" and still debating between hankook, michelin and pirelli slicks. Hankooks run the widest and correct for such rims, michelin are a bit narow in the rear and Pirelli maybe too narrow for me.

I have seen you are using the same tires as for 991.2TT/S, are you sure they will work? I mean the F/R ratio for the GT2RS should be different as they use a huge rear tire, what am I missing here?

Jean

Your McL is stunning Pepinoazur, the ultimate track weapon! The effort we need to put on these cars to keep up with the 720 is quite frustrating. The Pirelli DH is a great tire unless you really are looking at the last tenth of a second, they last a decent amount of time. Michelin soft will be up to 1s faster depending on the track if you find the right sizes.

Both the front and rear are about 2-3% smaller than stock so the ratio is ok. Rake is what I expected to change, measured it 0.5deg at the sill with stock tires and 0.1 deg with the slicks, that will anyway be changed with the ride height changes I will be doing. For sure traction under acceleration will be impacted because of the smaller tires, I am hoping the grippier slicks will compensate. ABS and TC remains to be seen. The Clubsport runs a similar setup also.

pepinozaur

Lets do some math to explain beter what I meant:
265/30/20 front OEM tire is Cup2 - 27.3"
325/30/21 rear OEM Cup2 - 28.7"
So OEM R/F ratio is 1.051


Pirellii 275/675 tire is 27.1" tall
Pirelli 315/705 tire is 27.75" tall
So the R/F ratio will be 1.024


I have observed this as GT2RS runs different ratio R/F compared to 991TT/S, and I know you have used this combo on your 911TT...
991TT 245/35/20 is 26.8 and rears 305s are 27.2 so ratio is 1.015, pretty close to 991TT oem, so maybe choose a bigger tire, that would help you. The only gain with a smallwer tire might be shorter gears so helping out acceleration.
710 tall tire would be perfect as 710/675=1.05 as OEM ratio.

Jean

Pepinoazur, yes you’re right that’s the math, but theoretical numbers are based on unladen specs, and different than the real world, tire pressure changes alone can impact 2-3% the rolling circumference, so is weight distribution, downforce, rake etc.. Those 2-3% variances are a none issue, especially for a 2WD.

pfbz

Yowza.... that looks like fun. Will the 19" forgelines fit with pccb's?

pepinozaur

Jean just wondering, why using a gt2rs on slicks and not a cup car instead? I leaning into endurance type of races besides time attack and I might just consider a Cup car or maybe 992 GT3RS with slicks conversion for 2022

Randyc151

I skipped the Cup because I want the option of driving on the street sometimes, too, and I don't have interest in racing. For enduro racing, I'd get a Cup car for sure.

Jean, once you've tested those new Forgelines on the track and confirm they are fantastic, I'd love to know the final sizes and offsets and specific tire models. I'll let you go first, but will follow closely after for this season.

Jean

Owning a Cup for frequent track use or endurance racing is a no brainer I think, they’re amazing.

Its just a personal choice, I only owned 2 N/A Porsche cars ever, a factory 964 wide body and a 993 C4, about 20 years ago, since then its all turbocharged, even my 997 RSR has been turbocharged.

I only enjoy driving intense and short stints, which the time attack and hill climb provide, I barely even do open track days except for testing.

I also like the option of racing a street legal car, and by just swapping tires you have a nice track weapon. The turbo RSR would put seconds on any other competition in this area, not fun.

The 991 turbo with it’s full interior comfort seats and stock bodywork at the UAE time attack was only 1 second behind a full blown 700 hp EVO X with a team of 8-10 mechanics, weighing maybe 1000 lbs less, and insane bodywork and aero that’s more fun for me than winning.