Anti-Squat Explained: Rear Geometry, Traction, and Launch
Accelerate hard in a rear-drive car and the tail sinks. Load is transferring to the rear axle and compressing the rear springs. Anti-squat is rear suspension geometry that carries part of that load through the suspension links rather than the springs. It is the acceleration counterpart of anti-dive, and it has a large say in how a car puts power down.
The 100% line
View the car from the side. Find the rear suspension's side-view instant center — the point the rear links' lines converge toward, usually somewhere ahead of the rear wheel. Then draw the force line to it. Where that line starts depends on the type of rear suspension:
- Solid (live) axle — from the rear tire's contact patch, because the axle housing reacts the drive torque through the links.
- Independent rear suspension — from the wheel center, because the differential is bolted to the body and the links only carry the thrust.
Now picture a reference line from the rear contact patch up to a point at center-of-gravity height directly above the front axle. That line has a slope of center of gravity height divided by wheelbase. A force line at that slope gives exactly 100% anti-squat: the links carry all the transferred load and the rear neither squats nor rises.
| Example input | Value |
|---|---|
| Wheelbase | 2,600mm |
| Center of gravity height | 500mm |
| Force line angle | 6° |
| Anti-squat | about 55% |
Those inputs are an illustration, not figures for any particular car.
What the percentage does
| Anti-squat | Under power | Notes |
|---|---|---|
| Below 100% | Rear squats | Usual for road cars; the springs take the remainder |
| 100% | Rear stays level | All transferred load goes through the links |
| Above 100% | Rear rises | Loads the tires very quickly; common on drag cars |
Load through the links reaches the tire immediately; load through the springs arrives as the suspension compresses. More anti-squat therefore hits the tire harder and sooner on throttle. That helps a drag launch on a sticky surface. On a bumpy corner exit it can make the rear feel rigid and break traction, because the suspension is less free to follow the road while power is applied.
Ride height changes it
Lowering the rear usually reduces anti-squat. The body-side link mounts drop with the car while the wheel-side mounts stay at wheel height, so the links tilt and the instant center moves down. A lowered car that squats more and struggles for traction out of slow corners is often showing this, and stiffer rear springs only mask it.
- Relocation brackets and adjustable link mounts — restore the link angles at the lower ride height on solid-axle and multi-link cars.
- Subframe spacers or raised subframe bushes — on independent rear suspension, raising the subframe relative to the body changes the angle of every link at once.
- Drop knuckles — lower the car at the knuckle so the links keep their original angles.
Changing link angles in side view also changes rear toe and bump steer behavior on a multi-link rear end, so the alignment is checked afterward.