Spyerx

Wow joe very cool. You can see horsepower at work you pull him on the 2 straight and back section but he's more aggressive in the corners and carries much more speed... Reeling you in slowly. Gt4 seems very stable and looks like there is more in it in stock form. Nice driving in both cars!

Manifold

Regarding alignment and setup, see discussion starting with this post:

https://rennlist.com/forums/991-gt3/...l#post12577288

Maybe the answer is: go factory, or go big cambers, middle ground is no man's land?

krisa9977

At Ascari I had almost 3 seconds lap time improvement after swapping Cup2 to Trofeo R.

krisa9977

Rear mid-corner snap oversteer is the biggest problem for 991GT3 when you drive the car 10/10th. This is due to active rear steering. To fight that oversteer you need softest rear bar setting, minimum 6mm rear toe in and a lots of negative camber in the rear. -3.6 degrees will solve this problem, but you'll get a lots of understeer. More front camber would help, but front camber is limited.

This is my fastest lap with -3.6 in the rear:

orthojoe

Thanks. Always interesting to read about what other setups people are trying out.

3 seconds is a huge difference. Based on what you are saying, that would mean between stock alignment/cup2 and track alignment/trofeoR there is a SIX second difference? I'm not sure all of that can be attributed to alignment/tires alone.

I've had 3 different capable drivers try out MPSC2 vs trofeoR on the same car and none of us are any faster on Trofeo R

You video show a significant amount of understeer. I see you are still adding additional steering input even after the apex and corner exit.
-3.6 camber in the rear is a crazy amount of camber for R compound street tires like MPSC2 and TrofeoR. It would be interesting to try it out, but honestly I'm so sick of tired of adjusting the car right now, I'm going to leave it.

My current setup:

-2.7 camber front (maxed out)
-2.4 camber rear
3mm total toe out front
6mm total toe in rear
Front bar stiff
rear bar middle

I might try to soften the rear bar since the car tends to oversteer still, but the current setup is predictable, controllable, and acceptable to me for now.

DeerHunter

If your set-up is predictable, exhibits reasonable tire wear and, more importantly, is fun, there's no reason to change it. Because, not racecar.

krisa9977

Motorsport is much more complicated. It is not that simple to do the math the way you do. The only way to find out what would be the difference is to take a professional driver, test all your settings and tires and then compare the results. It is quite possible that you can get 2 seconds difference between stock alignment/cup2 and track alignment/trofeoR. Or you can get 3,5 or 8 seconds.

I drove Trofeo Rs on many different cars. Those tires, for sure, much faster then Cup2s.

Alignment wise you can do what ever works better for you, I just share my experience. If you use different tires, it might work completely different. To take maximum advantage from the tires and alignment you have to be very fast professional driver. If you don't drive your car competitively, factory alignment works best for most of the people.

orthojoe

I'll buy 2 seconds (mostly because of alignment), but you said earlier that cup2 to trofeoR alone gave you 3 seconds, and stock alignment to track alignment alone gave you 3 seconds as well.

We will have to agree to disagree on that one. Accelerometer readings show no difference in lateral G grip between trofeoR and MPSC2 on a Gt3 with the same car, setup, and 3 different drivers.

Yes, the ideal setup for one person is not necessarily ideal for another person. Very true! Thanks for sharing your experience with us.

krisa9977

Unfortunately I didn't have much experience with TrofeoRs. When we were at Ascari we had a car with factory setup on Cup2 tires. We changed worn Cup2s and put fresh Trofeos. Next lap was 3 second faster on the same car. Keep in mind, that Cup2 were not new. If we swapped new Cup2s with new Trofeos, we might see different results.

Again, if you don't use your tires 100% in corners, it don't make any sense to compare two different tires. The only accurate test if you drive the same car, same day with pro driver.

krisa9977

I think this is very accurate test of Michelin Cup2 and Pirelli Trofeo R:

2:02 Cup2
2:00 Trofeo R

orthojoe

Worn cup2 and fresh TrofeoR most definitely can be a 2-3 second difference. No doubt. That is not a fair comparison, and you are presenting tainted information when you claim it is 3 seconds faster.

When I say that cup2 and TrofeoR are no different in grip, that is based on data collected and lap times collected from fresh, new tires so it is a fair comparison.

I'm not a pro, but I don't think I'm as bad of a driver as you think I am. You don't have to be a pro to be able to appreciate whether or not a tire has more grip than the other. Of course a pro can extract more than me, but that doesn't mean I can't take advantage of a stickier tire.

orthojoe

That damn video is starting to make me despise Chris Harris for being a sellout.

That video is just as good as your worn cup2 and new Trofeo R test.

I challenge anyone to do exactly what I did and conclude a different result.
- new MPSC vs new Trofeo R
- same track
- same driver
- same alignment/suspension setup
- similar weather conditions
- reasonably fast lap time

krisa9977

I'm not saying that you are bad driver. In fact, based on what you are saying about mid-corner oversteer, I can see that you drive the car at the limit. This is why I wanted to help you to solve your problem. Have no idea why you had such a bad experience with Trofeos. May be tire pressure or just defective set of tires. All sets a little different, especially Pirellis.
I had a set of Trofeo Rs that I couldn't balance. The rim was spinning inside of tire, no matter what you do.

Nevertheless, I drove Trofeos at Nurburgring and Spa Francorchamps with Porsche GT3 997 and had a chance to compare them with brand new sets of Cup2s. The difference was huge. I think that 2-3 seconds is the real number for 3 miles long track.

Well, I guess you know better, so good luck.

Manifold

Seems very likely that Trofeo R will want a different alignment than Sport Cup 2, so alignments and tire pressures would need to be separately optimized for each to really compare them.

But the other big aspect is how worn the tires are, as already noted. I now have over 11K miles on my GT3, and haven't simultaneously had new front and new rear tires on the car since I first got the car. The front tires definitely wear much faster than the rears, but I'm becoming convinced that the rears heat-cycle out long before they wear out, and the reduction in grip is very noticeable. So as I keep changing front and rear tires at different times, my car keeps changing its understeer vs oversteer characteristics, and its overall grip level, and I just keep adapting to it. Considering all of this unavoidable tire-related variability, I'm inclined to not mess around with alignment and sway bars much (currently at totally factory settings, with target hot pressures around 33/34), and instead just go with something 'good enough'.

Another consideration with the really big (3+) cambers is how they might affect the drivability of the car on the street, for those of us who drive to/from the track. With the factory alignment, I find the car to feel significantly better on the road - with less heavy steering feel - as compared to 2.0 cambers.

krisa9977

If you keep factory alignment it is very important NOT to drop your car!