What is the trac off button in your car what does it do and why is it there?

This turns off the traction control feature. Most people should not press this button. There are, however, certain situations in which it can be useful:

1) Useful during diagnosis of a mechanical problem.

2) As a workaround if a dangerous system problem with the traction control is known but repairs may need to wait a few days.

3) Enabling dynamometer testing (for power or emissions) on a 2 wheel drive vehicle.

4) On front wheel drive vehicle, to prevent cyclical gyrations of the Power Steering during excessive hard acceleration (machine controlled by negative feedback).

5) On rear wheel drive vehicles, expert driver may wish to use high torque to break traction for a controlled slide around a turn.