Orthojoe's track build journal
#1276
Rennlist Member
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!
#1277
Rennlist Member
Join Date: May 2012
Location: Mid-Atlantic (on land, not in the middle of the ocean)
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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?
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?
#1278
The car never felt quite as planted as it did with our first setup (-2.6F/-2.4R). Power out with corner exit, which is supposed to be a strength for the rear engine, just hasn't been there.
I don't know if it's the tires (trofeo vs cup2) or the setup, but I think running -3.0 in the rear was part of the problem. We'll see...
I don't know if it's the tires (trofeo vs cup2) or the setup, but I think running -3.0 in the rear was part of the problem. We'll see...
#1279
This is my fastest lap with -3.6 in the rear:
#1280
Nordschleife Master
Thread Starter
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?
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?
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
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:
This is my fastest lap with -3.6 in the rear:
-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.
#1281
Burning Brakes
#1282
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
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
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.
#1283
Nordschleife Master
Thread Starter
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.
#1284
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.
#1286
Nordschleife Master
Thread Starter
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.
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.
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.
#1287
Nordschleife Master
Thread Starter
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
#1288
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.
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.
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.
#1289
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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.
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.
Last edited by Manifold; 09-11-2015 at 07:26 AM.