Anti-Squat Calculator

Floor it in a rear-wheel-drive car and weight piles onto the back axle, compressing the rear suspension. That compression, called squat, eats into the travel you need for bumps and shifts the car's balance under power. Anti-squat geometry fights back: the angles of the rear control arms turn the driving force into an upward push on the chassis as you accelerate. The anti-squat percentage measures how much of the squat that geometry cancels, where 100% keeps the rear sitting level under full throttle. Enter your link angle, lever arm, and center of gravity height to get the percentage, or supply any three of the four values to solve for the last one.

What is anti-squat?

The effect comes down to torque. When the rear wheels drive the car forward, the engine's torque reacting at the contact patch creates a moment that wants to rotate the rear of the car downward. Angle the rear control arms the right way and that same driving force gets redirected into lifting the chassis instead of dropping it.

What controls the effect is the side-view angle of the line through the rear control arm mounting points. Steeper angle, more anti-squat. The number is written as a percentage of the theoretical maximum, where the maximum is the geometry that would cancel acceleration squat entirely.

At 0%, the geometry does nothing and the rear squats fully. At 100%, it holds the rear level under power. Go past 100% and you get "pro-rise," where the rear actually lifts as you accelerate. Drag racers chase this on purpose to drive the tires into the track at launch.

How to use this calculator

Enter the suspension link angle, the lever arm (roughly your effective wheel radius), and the center of gravity height to read the anti-squat percentage. Need a different unknown? Fill in any three of the four values and the calculator solves for the last one.

The link angle is what the line through your rear control arm pivot points makes with the ground when you view the car from the side. The lever arm sits close to the wheel's rolling radius. CG height is the vertical distance from the ground up to the car's center of mass. Each field has a unit dropdown, so you can work in metric or imperial.

Understanding the formula

The percentage comes straight from the side-view geometry of the rear links and the height of the center of gravity:

Where $\beta$ is the suspension link angle, $L$ is the effective lever arm (wheel radius), and $h$ is the CG height.

Worked example: Take a sports car with a CG height of 0.4 m, a suspension link angle of 15 degrees, and an effective lever arm of 0.3 m.

First, find the tangent of 15 degrees: $\tan(15°) \approx 0.2679$. Multiply by the lever arm: $0.2679 \times 0.3 = 0.08037$. Divide by the CG height: $\frac{0.08037}{0.4} = 0.2009$. Multiply by 100 to get the percentage: $0.2009 \times 100 \approx 20.09\%$. The geometry offsets about 20% of the acceleration-induced rear compression.

So a steeper angle and a longer lever arm both push anti-squat up, while a taller CG sits in the denominator and drags it down. That is the reason lowering a car raises its anti-squat for the very same link geometry.

Applications

Target anti-squat depends on what the car is built to do. Drag teams often run over 100% to slam the rear tires down at launch and hook up off the line. Road racers usually land between 50% and 80%, giving up a little launch grip for suspension that still soaks up bumps mid-corner on throttle. Production cars sit lower, around 30% to 60%, because ride comfort matters more than the last bit of traction.

Off-road builds need a careful hand here, because aggressive geometry turns harsh over rough ground once you are on the power. Independent rear suspension and a solid axle lay out the geometry differently, so you find the effective angle a different way, even though the math underneath stays the same.

Tips for suspension setup

Measure where your car sits now before you touch anything. The geometry is touchy: a swing of two or three degrees can move the percentage by five to ten points. Take the reading at ride height with the tank and fluids full.

More anti-squat keeps the rear from dropping, but it can stiffen the ride when you are accelerating. If the back end binds up or hops over bumps under power, you have probably dialed in more than the surface wants.

Frequently asked questions

What is a good anti-squat percentage?

There is no single right answer. Street cars are happy around 30% to 60%, track cars around 50% to 80%, and drag cars at 100% or more.

Can anti-squat be negative?

It can. Negative anti-squat, sometimes called pro-squat, means the geometry adds to the compression instead of fighting it. You rarely want that, and it shows up infrequently in practice.

Does anti-squat affect braking?

Not directly. Anti-squat only deals with the forces under acceleration at the rear axle. Braking has its own versions: anti-dive at the front and anti-lift at the rear.

How do I measure the suspension link angle?

Set the car at ride height and find the rear suspension's instant center in side view. Then measure the angle of the line running from the rear contact patch through that instant center, relative to horizontal.

Why does lowering a car affect anti-squat?

Dropping the car moves two things at once: the CG height and the link angles. A lower CG (smaller h) pushes anti-squat up, but the new arm angles can cancel or amplify that, so the only way to know is to run the numbers again after any ride height change.