Handbrake turn

The handbrake turn (also known as a bootleg or bootlegger's turn) is a driving technique used to deliberately slide a car sideways, either for the purpose of quickly negotiating a very tight bend, or for turning around well within the vehicle's own turning diameter.

Technique

The driver starts by using steering input to transfer weight to the outside tires; the handbrake is then used to lock the rear wheels, thus upsetting the adhesion between the tires and the road surface. With practice, the car can be placed accurately by releasing the handbrake and accelerating the vehicle. The technique is used in some forms of motorsport, for example rallying, autotesting, drifting and motorkhana.

Many sports cars, especially UK makes such as MG and Triumph, as late as the early 1970s were offered with a fly-off handbrake option for competition purposes—the button on the end of the lever has to be pressed before the brake will lock on, which is the reverse of the normal arrangement—allowing for faster and more controlled application in a handbrake turn, and less liable to be accidentally locked on while doing such a maneuver.

In a rear-wheel drive manual transmission vehicle, it is also necessary to operate the clutch to prevent the handbrake from stalling the engine.

Physics involved

In a normal turn, without wheels sliding, rear wheels follow the front ones because resistance to motion in the forward direction is significantly lower than in the sideways direction. Lateral resistance (tyres' static friction) provides the centripetal force that makes the rear end of the car follow the turn. When the driver locks the rear wheels with the handbrake, both directions offer the same resistance (kinetic friction). Due to inertia, the rear end tends to continue in the same direction, and slides out.