[James Blint]

is it true that biger value is less effect (ABS, traction control)?
on traction controls are number 1 to x and OFF

Test it by yourself, put the TC at 8 in a GT3 for example, you ll quickly feel the tail happiness 

High TC (1-2 in AC) can really limit exit speeds when in low gear and tight chicanes/hairpin, of course also prevents you to go sideways and kill the rear tyres too quickly. I would say at the point the rear becomes slightly alive on exits it means you have already exhausted most of the power you could put down without it, so that's where your TC more or less should be for a consistant race pace. Usual range for me is 3-5, i have it on one of my wheel's dial as well, sometimes i kick it down or up, wether to preserve the tyres or catch up, but i don't believe it's always worth the risk.