Anti-Lift Calculator

When a car brakes hard or accelerates, weight shifts between the front and rear axles. Under braking the rear end tends to rise, and under acceleration in a rear-wheel-drive car it squats down. Anti-lift geometry uses the angle and placement of the trailing arms to push back against that movement. Give it the suspension arm angle, the effective lever arm length, and the center of gravity height, and you get the anti-lift percentage of the rear suspension.

What is Anti-Lift?

Anti-lift is the rear-suspension counterpart to anti-dive. Anti-dive handles nose-dip at the front during braking; anti-lift handles the rear. When you brake, weight transfers forward and the back of the car extends, or "lifts." Accelerate in a rear-wheel-drive car and the opposite happens: the rear squats down.

Engineers set the rear suspension links at specific angles so the geometry generates a force that fights this vertical movement. The anti-lift percentage measures how much of the weight-transfer motion the geometry cancels. At 0% the geometry does nothing to resist the movement; at 100% it would stop the movement entirely. Nobody chases 100% in practice because it wrecks ride quality, so most production cars land between 15% and 30%, trading a little body control for comfort.

How to Use the Anti-Lift Calculator

Enter any three of the four values and the missing one fills in. By default you give the arm angle, lever arm length, and CG height, and read back the anti-lift percentage. To solve for something else, clear that field and fill in the other three. Each field has a unit dropdown for switching between metric and imperial. A worked example from a rear-wheel-drive sports car is already loaded, so you have numbers to start from.

Understanding the Formula

The anti-lift percentage comes from this relationship:

Here, $\phi$ is the angle of the rear trailing arm relative to the ground, $L_s$ is the effective lever arm from the pivot point to the wheel center, and $h$ is the height of the center of gravity above the ground. The tangent of the arm angle does most of the work here. By angling the trailing arms up or down, you change how much leverage the suspension has against the torque from weight transfer.

Take a rear-wheel-drive sports car with a CG height of 0.45 m, a suspension arm angled at 12 degrees, and an effective lever arm of 0.4 m.

First, compute $\tan(12°) \approx 0.2126$. Multiply by the lever arm length: $0.2126 \times 0.4 = 0.0850$. Divide by the CG height: $\frac{0.0850}{0.45} = 0.1889$. Finally, multiply by 100 to get 18.89% anti-lift. So the suspension geometry cancels roughly 19% of the rear lift that would otherwise happen during braking. The springs and dampers handle the other 81%.

Applications

Anti-lift geometry comes up in a few places. In motorsports, teams tune link angles to keep the rear contact patch flat against the track through braking zones, which helps both stability and stopping distance. Road car engineers weigh anti-lift against ride comfort and usually aim for 15% to 30%. Off-road builds run lower values to keep suspension travel over rough ground. It also matters when you design custom suspension for a track build or move factory mounting points to change how a car handles.

Tips for Suspension Geometry Design

Push anti-lift much past 50% and the suspension starts to bind under load, giving a harsh, unresponsive ride. Most production cars sit at 15% to 30% for good reason. The geometry that's good for anti-lift under braking usually fights anti-squat under acceleration, so you end up designing for a middle ground based on how the car will be used. Small changes at the mounting points move the anti-lift percentage a lot, so measure carefully before you cut anything.

Frequently Asked Questions

What is a good anti-lift percentage?

Most road cars run 15% to 30%. Race cars sometimes go to 30-50% depending on the circuit and driving style, though very high values cost traction on bumpy surfaces.

What happens with 0% anti-lift?

The suspension geometry does nothing to resist weight transfer movement. The rear end lifts freely during braking and squats freely during acceleration, relying entirely on springs and dampers.

Can anti-lift be too high?

It can. Very high percentages make the suspension bind, which feels stiff and can cause wheel hop and lost traction, especially when you accelerate out of a corner over uneven pavement.

How does anti-lift differ from anti-squat?

Anti-lift deals with rear suspension extension during braking; anti-squat deals with rear suspension compression during acceleration. Both use link angles to resist weight transfer, but they need different geometries and usually pull against each other in design.

How do I measure the suspension arm angle?

Measure the angle between the rear trailing arm (or equivalent link) and the horizontal ground plane with the vehicle at its normal ride height and the suspension at design position.