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What is Anti-Squat?

"Anti-squat uses suspension geometry to control weight transfer. Learn the physics behind instant centers and why adjustable rod ends are essential for tuning maximum traction."
Anti-Squat of rear suspension demonstration

What is Anti-Squat?

Have you ever watched a drag car launch? You might notice the rear end doesn’t just sit down; sometimes, it actually rises. Conversely, on a stock street truck, hitting the gas usually makes the rear bumper dip low. This phenomenon is controlled by a suspension geometry concept called Anti-Squat.

For fabricators and racers building custom 4-link or 3-link suspensions, understanding anti-squat is critical. It determines how your vehicle plants its tires, handles weight transfer, and behaves under heavy acceleration.

1. How Anti-Squat Works?

When a vehicle accelerates, weight naturally shifts from the front to the rear due to inertia (Weight Transfer). This usually causes the rear suspension to compress, or “squat.”

Anti-Squat is a mechanical force generated by the angle of your suspension links (control arms) that fights this compression.

  • 0% Anti-Squat: The suspension relies entirely on springs and shocks to manage the weight transfer. The rear end will squat significantly.

  • With Anti-Squat: The geometry of the control arms converts some of the forward acceleration force into a vertical “lifting” force on the chassis.

Think of it like pushing a heavy box. If you push horizontally, you just move it forward. If you push it slightly upward while moving it forward, you are technically lifting some of its weight. Anti-squat is your suspension links “pushing up” on the chassis.

2. What Do Anti-Squat Percentages Mean?

Anti-squat is measured in percentages. This value tells you how much of the weight transfer is being resisted by the suspension geometry versus the springs.

  • 100% Anti-Squat: The mechanical leverage of the links perfectly cancels out the weight transfer. The rear suspension will neither compress nor extend during acceleration.

  • Less than 100% (e.g., 50%): Common in factory vehicles. The geometry does some of the work, but the springs handle the rest. The rear will squat slightly, providing a comfortable, compliant feel.

  • More than 100% (e.g., 120%): The lifting force is stronger than the weight transfer. When you hit the gas, the rear of the car actually rises (Anti-Rise). This drives the tires harder into the ground.

3. How to Calculate and Adjust Anti-Squat?

To find your anti-squat, you need to find the Instant Center (IC):

  1. Draw a line extending from your upper control arm.

  2. Draw a line extending from your lower control arm.

  3. The point where they intersect is the Instant Center.

The position of this Instant Center relative to the vehicle’s Center of Gravity (CG) determines your percentage.

  • To Increase Anti-Squat: You need to move the Instant Center higher or further back. This is usually done by raising the upper link mount at the axle or lowering the lower link mount at the frame.

  • To Decrease Anti-Squat: Make the links more parallel, moving the IC further forward or lower.

This is why custom chassis builders use adjustable 4-link systems. By using L/R threaded Rod Ends, you can fine-tune arm lengths and move mounting points to dial in the perfect geometry for your specific track or terrain.

4. Anti-Squat Application Strategies:

Anti-squat is not “the higher, the better.” It is a trade-off between traction and suspension compliance.

A. Drag Racing

  • Target: >100%

  • Reason: They want to “plant the tires.” By forcing the axle down and the chassis up, they maximize the initial bite of the tires.

  • Trade-off: The suspension becomes very stiff under acceleration. If the track is bumpy, the tires might skip or chatter (tire shake) because the suspension can’t absorb the bumps while under load.

B. Rock Crawling

  • Target: 50% – 80% (Subject to debate)

  • Why: Helps keep the front end down on steep climbs.

  • Trade-off: If anti-squat is too high (>100%), the vehicle can experience “jacking,” where the rear lifts too high, raising the center of gravity and increasing the risk of rolling over. If it’s too low, the rear squats too much, dragging the bumper on obstacles.

C. Desert Racing / High-Speed Off-Road

  • Target: Lower (20% – 50%)

  • Why: Suspension compliance is king. When hitting whoops at 80mph, the suspension needs to move freely. High anti-squat makes the suspension bind and stiffen when on the gas, causing the rear to kick violently over bumps.

Conclusion

Anti-squat is the art of using geometry to control chassis movement. It allows you to tune how your car launches and handles without changing spring rates. However, theory is useless without the right hardware. To achieve the perfect anti-squat curve, you need precise adjustability.

author avatar
Danny Ni Engineering & Mechanical Systems Writer
Danny Ni is an engineering-focused technical writer at SYZ Machine, specializing in mechanical components, linkage systems, and real-world application engineering. His work covers aftermarket vehicle parts, industrial joints, and mechanical principles, translating complex engineering concepts into practical insights for engineers, fabricators, and industry buyers.
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