Agree with you CNG, your right there.
The default settings for a LMP/Group C car is 63/88 and that is the max downforce you can get.
So the Sauber Mercedes C9 Race Car would class in that category. It is the same for a Playstation Pescarolo Judd, Nissan R92CP, Toyota GT-One. Bentley Speed 8, Mazda 787B etc.
I would not recommend full downforce unless if you are on a tight and twisty track where grip is important. E.g. In Circuit De La Sarthe 2, a 50/70 - 55/77 downforce will be enough to tackle the long straight to get max top speed and still have enough grip in the corners if you can get a good setup.
Remember downforce is not the only thing that is vital to a setup as it only affects the car at high speeds. The suspension, transmission, LSD and brakes settings as well use of tyres all count to a good setup. In addition, the tuning of suspension affects grip of a car most.
Mostly setting up a car is trial and error, till you can get it right.
Thats my 2 cents worth and hope that helps.
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