Manifold

Good info. What, if anything, do you see as the weak points of the 991.1 GT3 or RS for handling the higher G-forces? What needs to be beefed up?

Joe731

FYI,

I checked with Forgeline to see if their 18" wheel would fit over the 380mm steel rotor, given than the 19" fits over the 410mm ceramic rotor, but they looked at their drawings and data and said it won't fit.

Martini991RS

TRAKCAR,

Can you share some insight on why the R7 is the only tire that will work? The Pirelli 19" slick with 255/325 seems like it would fit to me?

M3irish - planning on doing 19" with PCCB based on your experience do you think Forgeline or HRE can build something custom with bigger concave to avoid grinding the caliper?

Martini991RS

Joe which specific forgeline 19's fit the ceramic rotor? Is there any grinding on the caliper like in m3irish picture? Do you have a picture of the 19 forgeline with ceramic?

Thanks in advanced super excited to see your post haha

C4SGRPDK

Some research I did

you would need to run #1 front with #1 rear or #2 front and #2 rear.

these are the pirelli ferrari challenge slicks


GT3 RS OEM tire size

Front: tread width 9.1’’ /// overall diameter 27.3''

Rear: tread width 12.1’’ /// overall diameter 28.7''


2 choices of front tires :

#1 - Pirelli P Zero Slick 235/645-19 DH

- tread width 9.25’’ /// overall diameter 25.4’’ (0.15’’ wider et 1.9’' lower than OEM)

#2 - Pirelli P Zero Slick 255/650-19 DH

- tread width 10’’ /// overall diameter 25.6’’ (0.9’’ wider et 1.7’' lower than OEM)

2 choices of rear tire:

#1 - Pirelli P Zero Slick 295/680-19 DH

- tread width 11.6’’ /// overall diameter 26.7’’ (0.6’’ narrower et 2.0’' lower than OEM)


#2 - Pirelli P Zero Slick 305/690-19 DH

- tread width 12’’ /// overall diameter 27.1’’ (0.1’’ narrower et 1.6’' lower than OEM)



Can anybody chime in on these?

Joe731

I have steel rotors, so I was inquiring specifically about the possibility of 18" wheel fitting over steel, which is does not.

I winter my car at Autoquest of SW Florida, and there are several others who do the same with 19" over ceramics. You can call Gavin at Autoquest for more details (Forgeline Dealer) or call David at Foregline. They are a board sponsor.

They will tell you they fit, but that it is tight and you will have clag and gravel issues, but many still do it.

David Schardt
Forgeline Motorsports, LLC
3522 S. Kettering Blvd
Dayton Ohio 45439

http://www.forgeline.com
800-886-0093

Martini991RS

Joe,

Thanks for the detailed info!

m3irish

Both companies are open to custom sizing work. I'm not sure on adding a concave section. I'd give them a call. As a side note the HRE and Forgelines are going to have the same clearance issues.

Another thought is switching to the steel calipers. It's pretty reasonable for p-car prices. Might be cheaper than custom one off wheels.

TRAKCAR

Sorry, that is only based on having zero feedback on slicks and those tires to confirm they work. In theory, if they are within 3% it should work.
Most I think are reluctant to try slicks as the manual states it voids warranty.

Very interesting, surprised that no one has tried, but maybe they have and do not want to publish the findings.

Martini991RS

Thanks for the feedback guys. Our team is around 3-4 months away from slicks will be sure to publish/update you all when we have something. Car is turning a year old now. Have gone through quite a few sets of cup2s and trofeo Rs. Tires are hella expensive so looking forward to the 19's to save on tire costs. Yokohama also has slicks for 19's looking at that option as well.

So far for us the trofeo Rs are about 1.5-2 seconds faster on a 2 minute lap. Shaved about 3 seconds when we switched to trofeo R with a dsc sport controller, bbi arms package (minus springs) and bigger rear wing. Track Conditions similar. We try to use brand new tires when setting reference times so unfortunately it would cost a lot of money to only change one thing at a time. Right now there's definitely more time to be had in the car as the stock springs are bottoming out.

Will be getting new springs in 2-3 weeks will test again then. Didn't get springs from bbi cause they wouldn't give us their spring rates which is fine but wanted to know the specific rates cause want to play around with spring rates.

Currently working with dsc on a customized solution for the RS dampers that will accomdate the trofeo R and full slicks in the future.

Any recommendations on HRE vs Forgeline on which is lighter weight / better clearance for the 19's?

Hopefully our fully built RS will be able to lap as quick as a cup car which is about 8 seconds faster stock to stock on the local circuit. Close to half way there. Right now with slicks and everything else we have going we are expecting to shave around 7 seconds give or take a second. Might need a more aggressive front splitter and aero package to get to the last second. Front of the car feels a little light through high speed corners.

TRAKCAR

Wow!!


Man, keep it coming please, I'm hanging on your lips!
Just installed the DSC controller, courtesy of Dundon.
Otherwise stock.
Testing this Saturday at Sebring. Like you, I am doing one adjustment at the time.
I will swap oem controller back before the end of the day to have apples to apples comparison.

8 seconds is huge. CUP car times vary a lot but at Sebring I run now 2:16's on MPSC2.
Hoosier 2-3 seconds faster, slicks 4-5 and I figure more with suspension to deal with the extra grip.

Just concerned about warranty and the computers keeping up...

Thanks for posting, keep it coming!

Martini991RS

I'm a new poster but I have been following the forums for a while now and I know TRAKCAR is one of the most respected drivers here but danggggg looking at one of the best drivers of the forums' PB of 2:16 and the fastest IMSA 991 cup times in sebring of 2:03.5 seems like even with whatever upgrades (no turbo/crazy engine upgrades) the RS will never be as fast as a cup car =(

The goal with the RS was to make it as fast as a cup car using things that were restricted for the cup car like upgraded headers, active suspension, 4 way steering, PCCB and a more aggressive aero/splitter/wing/diffuser. I was inspired by the "RS Cup Edition" post a while back

8 seconds doesn't seem like a good enough target. Looks like need to target 12 seconds?? On the flip side the slowest cup car time was 2:10-2:11 so I guess with full slicks TRAKCAR will be head to head with the backmarkers

TRAKCAR

Its interesting!

Martini991RS, what is your local track you are testing on?

For example GT4CS, seems to about be the same as a stock GT3RS at Sebring, I maybe can give some of those a hard time but CUPS not so much.

Pretty much all CUPS are XX seconds faster then the GT4CS, but I don't know the delta.

I'm only fast-ish at hometrack Sebring and otherwise only been to PBIR and Homestead in the US with the 991RS to compare to Rennpoints CUP lap records, but I don't know CUP classes.
I have some laptimes from European tracks, but clueless what's fast and how laptimes compared to 997RS and CUPS.

The 991RS is about 3-4 seconds faster then the 997RS at Sebring and a 997RS would run a 2.15 on slicks at Sebring, 2.19RS on Nitto NT-01 which I think are very comparable to the MPSC2, depending on temperature.

Good stuff

porscheflat6

Yep, two weekends ago there was GT3 with brakes, hubs, and cup wheels so he could run Michelin cup slicks. $$$$ to convert the street to these cup parts.

Martini991RS

TRAKCAR - I'm running from the Philippines, local circuit called Clark International Speedway. There are no cup cars here. I did my estimate based on last year's evo article featuring the GT3 the RS the cup car and the RSR.

I got the times from the latest round of the IMSA GT3 CUP Race. I'm assuming they are running the 991.2 cup cars hence a little faster than last year.

http://porschegt3cupusa.imsa.com/sch...=62&sessid=318

Last year's fastest in Round 1 was 2:08.153 and for Round 2 it was 2:07.230 http://porschegt3cupusa.imsa.com/por...orical-results

Based on our little computation your 2:16 with slicks some help with suspension some aggressive canards, splitter bigger win lighter seat exhaust etc should get you to 2:08 hopefully

porscheflat6 - there we go confirmation there are people running slicks and not sharing with the community. To be expected I guess, generally most of the people I have met in the motorsport community are a little bit secretive when it comes to their setup and their secret sauce =D

Don't want to be a hypocrite hiding my setup so here are a few pics haha =) There are DMS headers on, a DSC controller and a lightweight battery as well.