tweak
First you have to check the tweak, then you have to adjust the tweak. To check the tweak set the car on a tweak board (just like you do for 1/10 TC) or use another method, such as the coin drop method. If the car is not level (tweaked) then you must adjust it.
Most t-bar cars have tweak screws at the front of the t-bar for adjusting tweak, screw one side in and the other side out an equal amount untill you get the car level.