Bill Lehman

When I test fit my new CCW 11" R (44 offset), I noticed light contact and bent the bracket a little for clearance. There were no issues with my OZ 10" (40 offset).

Manifold

Is there a near consensus on optimal track setup for the GT4?

This past weekend, I had a chance to track my wife's stock GT4 back to back with my 991 GT3, and the GT3 seemed way more buttoned down overall. The GT4 can do a decent lap time, but seems 'floppy' compared to the GT3. Both cars on Cup 2.

orthojoe

I'm not sure there is an optimal setup. As you have seen with the gt3, I've found that various setups from stock to aggressive camber and stiffer springs all drive about the same, save for tire wear.

I've found the GT3 to be more buttoned down on corner exit than the GT4. I think is a combination of
1) rear engine
2) rear wheel steering
3) more sophisticated rear suspension

gtreddy

What do you consider the normal suspension bits to get to your camber angles? I'm a bit confused looking at the track wiki and targets suspension package page since some of it doesn't line up. Do you have camber plates and drop links for front/rear?

doborder

2) Tarett front tie rods (to allow sufficient negative camber)
3) Tarett front adjustable thrust arm bushings / caster pucks (to correct excess caster from running negative camber)
4) Tarett cup lower control arm monoball ends (the oem thrust arm bushings are rubber and once you convert to solid bushings, preload is transferred to the oem rubber lca ends). The cup monoballs include a thick shim and longer threaded rods in order to run lots of negative camber if you desire)
5) Tarett rear toe links (to allow sufficient toe/camber adjustability)
5) Tarret standard rear lower control arm monoball end (not pictured) The factory rear thrust arm bushing solid, as mentioned by BGB, so I followed suit with BGB's recommendation and went with a solid monoball rear LCA end. The cup monoball isn't needed since you won't run as much negative camber in the the re

Page one of this thread
Ask orthojoe for specific camber target
I think I'm at from -3.1 and rear -2.7

orthojoe

New PB at Thunderhill running the cyclone configuration yesterday with the GT4. After a year of trying, I finally went sub 2:00 with a solid 1:59.4.

Here is the video:



I get a ton of questions about the setup, and it has evolved a tiny bit over the past year, so I will list it all out again.

Tires:
Bridgestone RE71R tires
20" 245/295 on OEM wheels
19" 245/285 on OZ 19x8.5 and 19x11 wheels
Target pressures 33-34psi hot on all 4 tires.

Suspension:
Stock PASM unit. DSC has been removed
Tarrett springs
Front and rear RSS XL LCA monoballs
Tarrett rear toe links, front tie rods, and front adjustable thrust arm bushings

Sway Bars:
middle front and middle rear

Front Alignment:
-3.2 camber
zero toe
9.0 degrees caster

Rear Alignment:
-2.7 camber
5mm total toe in (about 2.5mm each side)

Cantrell roll bar
Schroth 6 pt harnesses

Endless ME20 brake pads

AP J hook front rotors

Stock Diff.

Full interior.

ESC and TC ON

** This alignment/setup is what works for ME. It can and will be different for others based on driving style, track, and experience. I would adjust alignment based on tire wear only. My tire wear is fairly even at this point. If your wear looks even, I would not change anything.

TRAKCAR

Why DSC removal?

orthojoe

It didn't feel like it was doing anything anymore after I added the tarett springs, so I took it off to see if it would make a difference. Felt the same and removing it didn't slow me down

TRAKCAR

Makes sense.
Without going to springs it seems to help MPSC2 tire wear and/or allow softer sway bar settings.

orthojoe

Yeah. I didn't feel or see much of a difference after adding springs. Probably because the dsc was installed

orthojoe

I thought I'd post up an interesting data graph of my best lap times at Thunderhill in the GT3 vs the GT4.

The cars are fairly evenly matched up until turn 6 and then the GT3 just takes off. Apex speeds are pretty even too. The smoother lap was in the GT4. In the 3 I could have:
1) setup the car in T1 and T2 to get on the throttle earlier and exit faster
2) Entered T3 smoother
3) I entered and exited T5 better in the 4
4) Went in too hot for T9 in the 3 and scrubbed speed at the apex

Beantown Kman

Joe, I've never been to TH. But even without being able to open your data in RaceStudio some things stand out from the graphs you posted. Assuming the track conditions were similar and the tires were the same, you would expect your vMins in the corners to be within 2-3 mph of each other and they are. Most people find the 4 easier to drive at the limit than the 3 because it is so well balanced and this should show up in corner entry but it doesn't. Your vMins in the 4, however, do appear a little higher in most corners. And you do manage to get back to the throttle sooner in the 4 than in the 3. The 4 just can't keep up with the 3 coming out of the corners due to the large power difference.

Looking at the data, both laps appear to be well executed. The 2 second difference being explained largely by the difference in power between the cars.

orthojoe

Thanks, man. Yes, similar conditions and same tires. Getting back on the throttle with the 3 takes a bit more finesse and confidence, but the 4 is helping me get there. My best lap in the 4 is a better lap than my best in the 3.

Beantown Kman

Wow. That's impressive!

Making a strong commitment to the gas pedal on corner exit is not easy. But it's fundamental to fast lap times. Your line coming out of the corner is the key. I would expect you'd want to take a slightly different line on some corners with the GT3 than the GT4 to do what's needed. Joe, I suggest you get the first of Adam Brouillard's "The Perfect Corner" books. He's not the best writer but he's really smart and he has some great tactics to improve one's driving. They are unlike any other books I've read on driving/racing technique.

vantage

How do driving lines differ between the GT3 and GT4? I would expect that generally the GT3 might benefit from slightly later apexing because "in theory" a rear engined car might have ever so slightly worse apex speeds but better exit traction. But in practice, not sure...