[AmoryG]

When your robot turns, does it slow one side of the wheels down or speed one side of the wheel up? So in a tank drive you have say 4 wheels two on each side:

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To turn right you either need the left side of the wheels turning faster than the right:

f 
a
s
t

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Or turning the wheels on the right side slower than the wheels on the left:

                  s
                  l
                  o
                  w

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I think usually in traction control, if the robot's wheels are spinning faster than the robot is moving, the speed on wheels will be limited. If when turning you increasing the speed of one side of the wheels your traction control might be reducing their speed making the turn of your robot appear delayed.