Tire Shake

Tire shake is a violent shaking or vibration that occurs in drag racing when a vehicle's tires rapidly lose and regain traction with the track surface, causing the entire car to shake intensely rather than accelerating smoothly down the strip.

This phenomenon happens most commonly at the start of a drag race during the launch phase. When a driver releases the clutch and applies full power, the rear tires are supposed to grip the track and propel the car forward. However, when tire shake occurs, the tires begin to bounce and hop on the track surface instead of maintaining smooth contact. This creates a violent oscillation that travels through the entire vehicle, making it extremely difficult for the driver to control the car.

The root cause of tire shake typically involves an imbalance between the car's power, tire size, and track conditions. According to drag racing legend Austin Coil, tire shake happens for two main reasons: either too much tire spin or not enough. When there's excessive tire spin, the tires break loose completely and lose traction. Conversely, when there isn't enough spin, the tires try to grip too aggressively and begin to shake violently.

The physics behind tire shake involves the tire's sidewall behavior. Drag racing slicks have tall, flexible sidewalls designed to wrinkle and increase the contact patch with the track. When things go wrong, these sidewalls can wrap up and become momentarily square-shaped in tiny fractions of a second. This rapid deformation and recovery creates the characteristic violent shaking that defines tire shake.

Several factors contribute to tire shake. Launch RPM plays a critical role—too many revolutions per minute at the start can overwhelm the tires' ability to grip. The clutch settings matter enormously; if the clutch clamps too tightly or too loosely, it can trigger tire shake. The gear ratio in first gear also affects whether tires will hook up properly or start shaking. Even the tire size relative to the vehicle's weight and horsepower must be carefully matched.

Track conditions significantly influence whether tire shake will occur. A clean, well-prepared track with good traction helps prevent tire shake, while a track with less grip may require teams to adjust their suspension settings to compensate. Modern drag racing teams use sophisticated computer systems to monitor driveshaft speed and make real-time adjustments to the clutch or ignition system to prevent or minimize tire shake.

The consequences of tire shake can be severe. The vibrations are so violent they can break welds in the chassis, cause body panels and doors to fly off, and in extreme cases, have even knocked drivers unconscious. Beyond the safety concerns, tire shake costs valuable time during a race, as the car isn't accelerating efficiently while it's shaking.

Professional drag racing teams spend considerable effort finding the perfect balance to avoid tire shake. As drag racing pioneer Don Garlits explained, teams must walk a fine line—if the tire is too big for the available power, it will shake; if it's too small, it will just spin uselessly. Modern drag racing involves controlled tire spin throughout the entire quarter-mile run, but it must be precisely managed to avoid crossing into tire shake territory.