I don't know if it's a setup problem or physic model, but driving Ferrari 488 GT3 at Zandvoort (and Nordschleife) feels like the car is on ice. It slides too much and it's very easy to oversteer. I managed to fix the oversteering by moving rear wing higher, but then I lost even more grip. I don't like cheating, so I set proper tire pressures 170 - 180 kPa (with default ones problem still exists, but is less noticeable). Maybe it's a setup problem? Or perhaps, problem lays in driving model?
I oversteer at accelerating and when I'm releasing the gas pedal it's even more noticeable (which is probably expected, because front of the car gets more grip). However, I set pressures to 180 Front and 177 Rear and rear wing to P6 and it's much better now. I've also noticed I was going too fast on one of the corners by about 10km/h and now I can go much more cleanly. Problem is probably solved, but it would be nice to have descriptions of car setup options.
No, the track is green and the option to change it is unavailable from some reason. It's hard to tell if my driving style is appropriate. However, I've just managed to drop my laptime from 1.39 to 1.38 with updated setup (reply to lagg). I'm also beating 100% AI easily, but the AI is broken on this track. On Sebring it's much much harder.
If you change the weather to "Scripting" you can change the preset of the rubber. I don't know what's possible to change in this car, you can try changing the pump and the power of the differential, lowering rear springs and anti-roll bars, changing the throtle sensitivity and take more care accelerating.
Unless the setup is really really broken, you have much more to gain from driving style. From your few words I understand you suffer from load transfer front/rear like when you abruptly lift your throttle. It was taught me to learn to drive a car, to drive it with full tank and hardest tires : does wonder to learn to be gentle but firm with your inputs. When you drive like that, THEN setup changes make sense and you immediately see it working (or not).
@Comante I did like you said with full fuel and hard tires. My laptime dropped to 1.41. I'm always using throttle very aggressively. I need to work on this probably. Ps. TC and ABS was set to 6 entire time. With TC 2 and ABS 4 lap time dropped to 1.42. Would you recommend to practice with TC and ABS lowered?
I'm not a GT lover but I would say to learn to use TC and ABS to your gain. Remember that braking balance has a lot of influence in making the car willing to turn. This is an easy fix for over-understeer in turn entry.
Try increase front ride height (until you feels understeering), which shifts a little downforce to rear. Since you like to use realistic tyre pressure, aim Hot pressure in 27-28 psi range(that is commonly used in ACC), which is about 190 kpa after a few laps (180kpa cold pressure is a little too high and will lose some grip after gets hotter). Also making rear spring softer does not always help stabilize the car, but has chance to cause suddenly lose of rear grip and spinning, especially in high speed corners. It is best to find a balanced point (Anti-rollbar, packer, differential preload can be a great help for tweaking)
Ferrari is an oversteery car, can tell that from my GT Challenge adventures with it. However, you should "milk" that oversteer to get faster. The oversteer basically allows you to turn in and out of the corner faster. So I am not too sure about your setup, it probably made the car slower. I would also recommend setting the TC to 0, at least for hot laps. It can really "pull" you out of the corners, but obviously throttle control is required. There are someother setup things, but can't tell you all of it
Let me say that if you are driving in a green track, it's very usual lost of traction and bad braking because of a dirty track without rubber, so you have a slippery track. As someone told you, put Weather option in "Scripted" and you could change real road to "Light/Medium/Heavy/Saturated rubbered" but not in all tracks, there are tracks with only "Green" available in the first practice. Driving in a Medium/Heavy rubbered track is much better and real, you'll find a very different feeling, a lot more grip In fact, you are right, minimum cold pressures for these cars should be 170/180Kpa equal to 25/26 psi in dry conditions (1,8/1,85 bars). But I don't know exactly in Michelin tires, it depends from technical regulations in every competition. Low pressures are very good to improve traction in slow turns, you get much more grip with low pressures, car drives more slow in reactions but in general you gain a lot of time because good traction is the key being fast, further you can drive with TC and ABS very low that improve your lap time. When you drive normal pressures or high pressures, you lose traction but is better in high-speed turns, in general response is much better and you gets more top speed, this is good but finally your lap times will be slower than with low pressures. I don't consider 140kpa a cheat, sim allows it. In fact in iRacing a lot of cars you go with 130/140kpa for the same reason, that's the minimum now in GT cars. Well, if you decide to run "real" cold pressures I also suggest working on traction in your setup with soft springs and probably you'll need more aero downforce.
Now I did a deep research on Google, looking for new Michelin tires, I think they're using now Michelin Pilot Sport GT S7M/S8M/S9M Well, there is a lot of different tires for competition, it depends every car run different wheel dimensions, but in general recomended minimum cold pressure is 1,4 bar for this tyre in GT cars and 2,0 bar in hot conditions with the proper camber. So Studio-397 is right with tires 1,4 bar = 140 kpa = 20,3psi and hot optimum pressure recommended will be 2,0 bar = 200kpa = 29psi maybe 27/28 psi would be better I think because in real cars thay always go to minimum pressures If you play ACC where they use Pirelli tires that's official for SRO championships, you'll find 27,5 psi hot optimum pressure, but Pirelli cold pressure is 25/26psi, so maybe it works different to Michelin and obviously ACC simulates ambient and track temperature