Everything starts with the mechanical adjust of your brake, so make sure the car is breaking strong and even locking when you apply full brake at high speed, with this done go to the transmitter and adjust:
1. Point 90%
2. Stroke 80%
3. Lag 0.0 sec
4. Speed -3
If your track is cold or wet try Speed -4 or -5
If the car is still locking the wheels decrease the 1. Point
If the car is braking in long distance increase 2. Stroke and a little bit 1. Point
Keep trying something around the 1 and 2 but don't go too far from -3 to -5 in the point 4. Speed