Just my 2 Cents.
I will set up a car at 50% cross for starters but will rarely keep it there. It all depends on the track. If the track has more RH turns I will add cross +50%. If the track has more LH turns I will put -50% cross in the car.
Example: Mid-O is run clockwise thus more RH turns. To top it off two of the RH turns lead onto very fast straights (Keyhole and Carousel). Since there are more RH turns than lefts and two of the RH turns are key to fast times I want the car to turn right great. I will give up some LH turning capability to gain killer RH turns. So the Mid-O setup would be to add some cross (52-54% for me).
I will make the changes at the track to suit what I want the car to do. You don't need scales to do it. just make apposing changes equal and go run it. If you like the change come in and try some more. Just make sure you write down what you did.
Example: You want the car to turn RH better. Take a 1/2 of a turn out of the LF and RR. Put a 1/2 turn in on the RF and LR.
You can also change rake to adjust oversteer and understeer.
Example: The car is tight (Understeer) (Pushes). Lift up the rear end and drop the front 1/2 turn and go run it. If you like the change try some more. If you are already low in the front just raise the rear.
It is very important to get a base setup. Cross, Ride Height, toe, camber and caster. But donít hesitate to change it. Try it. Learn from it.
Every track I go to has a different set up. Every track is different. The is no such thing as the perfect setup for every track.
Another note. What set up works for one person may not work well for another. Everyone has their own style.
When I race SM one of the only things we could do is change our setup. In the case of Mid-O I gained 2.5 seconds a lap by changing cross to 54%. One of my competitors was running 56% cross. Those who were behind us just left the cross at 50%.
When you get to a track and the car is not doing what you want it to, Change it. Donít fight it, Fix it. Fear not you can do it.