A clutch kick is a driving technique used in rear-wheel-drive drifting to disturb traction at the rear tires. The driver briefly presses the clutch pedal to disconnect the engine from the drivetrain, then releases it quickly while the engine is spinning at a higher speed. This sudden reconnection sends a torque spike through the drivetrain to the rear wheels.
The result can be enough wheel slip to initiate a drift or keep an existing drift going through a corner.
Key Facts
- Power flow in a rear-wheel-drive car is engine to clutch to transmission to driveshaft to differential to rear wheels.
- Torque at the rear wheels is approximately T_wheel = T_engine x gear ratio x final drive ratio x drivetrain efficiency.
- A clutch kick works by briefly reducing drivetrain load, allowing engine rpm to rise, then reconnecting the clutch rapidly.
- Rear tire grip is broken when drive force exceeds available friction: F_drive > μN.
- Angular acceleration follows τ = Iα, so a sudden torque spike can rapidly increase rear wheel rotation speed.
- A clutch kick is different from braking because it adds a sharp drive torque disturbance rather than reducing vehicle speed directly.
Vocabulary
- Clutch
- A device that connects or disconnects the engine from the transmission so torque can be transferred or interrupted.
- Drivetrain
- The system of parts that carries power from the engine to the driven wheels.
- Torque spike
- A short, sudden increase in twisting force delivered through the drivetrain.
- Differential
- A gear assembly that sends torque to the left and right drive wheels while allowing them to rotate at different speeds.
- Tire slip
- A condition where the tire's rotation or direction of motion does not fully match the vehicle's motion over the road.
Common Mistakes to Avoid
- Thinking the clutch kick makes the car faster, which is wrong because its main purpose is to break rear grip and control yaw, not maximize acceleration.
- Holding the clutch pedal down too long, which is wrong because the drivetrain stays disconnected and the torque shock may be delayed or too weak.
- Releasing the clutch without matching engine rpm, which is wrong because too little rpm may do nothing while too much rpm can cause excessive wheelspin or mechanical stress.
- Ignoring weight transfer and steering angle, which is wrong because a clutch kick alone does not create a controlled drift unless the car is positioned and balanced correctly.
Practice Questions
- 1 A car engine produces 220 N m of torque. The selected gear ratio is 2.1, the final drive ratio is 3.9, and drivetrain efficiency is 0.88. Estimate the torque at the rear wheels.
- 2 A rear axle supports 6000 N of normal force and the tire-road friction coefficient is 0.75. What is the maximum rear tire driving force before the tires begin to slip?
- 3 Explain why quickly releasing the clutch after raising engine rpm can break rear tire grip, even if the throttle position does not change much during the kick.