Line Lock

Line Lock

Line locks are designed to let the front and rear brakes work independently of one another. A line lock is a solenoid-activated valve that controls the flow of brake fluid. It is placed between the master cylinder and the brake calipers. A switch or button inside the car controls the line lock solenoid. Line locks are used in drag racing for burnouts and allow the front brakes to lock up while not affecting the rear brakes - allowing the rear tires to spin freely. Line locks protect the engine and rear brakes from undue wear.
When line locks first came out they were used as a launch tool for drag racing, but when trans brakes came out they became the better option. Now days, line locks are pretty much exclusively used for burnouts.A line lock can work one of two ways: 1. Keep brake fluid from leaving the front brake lines, 2. Block brake fluid from reaching the rear brake lines.
When used in the first example that keeps brake fluid from leaving the front calipers, the line lock is placed on the brake line heading to the front brakes. Apply the brakes and press (hold) the line lock button. By holding the button the valve stays closed keeping the brake fluid trapped in the front calipers. Now you can release the brake pedal and the car will remain stationary as long as you hold the button – leaving the rear wheels free to spin.In the second example of blocking brake fluid from reaching the rear lines, the line lock is placed on the brake line heading to the rear brakes. When you push the line lock button, and hold it, the solenoid closes the valve to the rear brakes, so when you do apply the brake pedal, fluid can only travel to the front brakes leaving the rear wheels free to spin. Installed in this fashion, you have more control over brake pressure and can creep forward toward the end of your burnout by slowly releasing the brake pedal.