[-)-MAILMAN-]

If you add the line like he said you can make both of your brake pedals work. Just keep in mind this just means that you can use either pedal to operate the brakes. The games does not support nor has a mod been made (that I am aware of) that allows for you to assign one brake pedal to the left wheel brake and the other pedal to the right wheel brake. Therefore you can't not use the brakes only to steer on the ground. The rudder is the only thing that lets you turn on the ground.

Keep in mind that if you go to the controls section while your game is opened this line will be erased the next time you open the game. If you change the file attributes to read only this won't happen, but if you then make any changes while the game is open they will be gone the next time you open the game. So if you are one who really never changes anything read only attribute may be the way to go.