Springs, dampers, and anti-roll bars

The one rule that fixes most setups

The end you stiffen loses grip. Stiffen the front springs or front anti-roll bar and the car understeers more; stiffen the rear and it oversteers more. The mechanism: a stiffer end takes a larger share of the lateral load transfer in a corner, which unloads its inside tire harder, and the pair of tires at that end gives up grip. Beginners get this backwards constantly — the instinct is to stiffen the end that’s sliding, which makes the slide worse.

So the fix is the opposite of where the problem is. Car understeering? Soften the front or stiffen the rear. Car loose? Soften the rear or stiffen the front. Almost every balance complaint resolves to that one sentence.

Springs — body control and the aero platform

Springs work in roll (cornering), heave (both wheels up over a crest), and pitch (braking dive, throttle squat). They do everything, which is why they’re a blunt instrument.

Soft vs stiff, when each wins

Stiffer springs transfer weight faster, cut body roll, and hold ride height steady — which on an aero car means steady downforce. GT3, GTP, LMP, and formula cars run stiff specifically to keep the floor and wing at a consistent height; the platform is worth more than mechanical compliance. Softer springs let the tire follow a bumpy surface and find mechanical grip, which is why low-downforce and road cars run soft. On a smooth track behind a GT3 aero map, go stiffer. On a bumpy street circuit or a low-DF car, go softer.

Front/rear spring split and balance

Set the car roughly neutral, then bias it slightly stiffer at the rear / softer at the front so you can rotate the car on throttle. Aim for a touch of understeer on long fast tracks where stability matters, a touch of rotation on tight slow tracks where you need the car to turn. Move spring rates in ~10% steps and change one end at a time.

Anti-roll bars — balance without killing compliance

Why ARBs are the safest balance knob

Anti-roll bars only resist roll. They do nothing in pure heave or braking dive, because both wheels move together and the bar doesn’t twist. That’s the reason ARBs are the preferred balance tool: you can shift steady-state cornering balance without changing how a single wheel absorbs a kerb. Springs change both at once; ARBs isolate the cornering effect.

Reading entry (front ARB) vs mid/exit (rear ARB)

The front bar shows up on corner entry. Stiffen it and you transfer more load to the outside front, inducing understeer at turn-in. The rear bar shows up mid-corner and on exit. If the car is tight through the middle or won’t rotate off the corner, stiffen the rear bar to free the rear. For power-down oversteer on exit, soften the rear: soften the rear bar, soften rear springs ~10%, and drop rear tire pressures a touch so the rear tires keep their footprint.

Dampers — bump and rebound

What bump and rebound actually do

Bump (compression) damping resists the wheel moving up — the spring compressing. Rebound (extension) damping resists the wheel returning down — the spring extending. Dampers don’t set where the car sits; they control how fast it gets there. They shape transitions, not steady state.

Fast vs slow (shaft speed, not car speed)

Fast and slow damping are sorted by how fast the damper shaft is moving, not how fast the car is going. Slow (low-speed) damping controls body motions driven by your inputs: roll, pitch, dive, squat. Fast (high-speed) damping controls wheel-only events: kerbs, bumps, road texture. Tune slow damping for balance and turn-in feel. Tune fast damping so the car soaks up kerbs without skipping or launching — if it bounces wild over a bump or a curb kicks it off line, take fast bump down a bit.

Using rebound to shape turn-in

Add front rebound and you slow how fast load leaves the front as you turn in, holding the nose loaded a moment longer for sharper initial rotation. Too much and the front jacks down, loses compliance, and starts skating. It’s a fine adjustment — make it after springs and bars are close.

Ride height and rake

Ride height sets the aero platform and your kerb clearance. Running the front lower than the rear gives forward rake, which generally adds front aero and rotation on a downforce car — a common starting point is the front two ticks lower than the rear. Go too low and the car bottoms out, gets curb-sensitive, and the floor clips at speed, so back off the moment you feel it skipping over kerbs.

An order of operations

Don’t open the setup screen and start everywhere. Work in this order, one change at a time, ~10% steps:

1. Tire pressures and temps — get the contact patch right first. See tires and pressures.
2. Ride height and rake — set the platform and kerb clearance.
3. Springs — for the surface and the aero platform.
4. Anti-roll bars — for steady-state cornering balance.
5. Dampers — for transitions and kerbs last.

If the sim gives you a fixed setup (iRacing fixed series, for instance), these are locked and this whole exercise is moot; open setups expose all of it, including the alignment numbers — camber, toe, and caster that work alongside springs and bars to set grip and turn-in. ACC, rFactor 2, and LMU give you explicit fast/slow bump and rebound on most cars.

Quick fix table

Symptom	Change
Understeer on entry	Soften front ARB/springs, or stiffen rear ARB
Understeer mid-corner / tight on exit	Stiffen rear ARB
Oversteer / loose mid-corner	Soften rear ARB/springs, or stiffen front
Power-down oversteer on exit	Soften rear springs ~10%, soften rear ARB, lower rear tire pressure
Car skips/launches over kerbs	Reduce fast bump
Lazy turn-in	Add a little front rebound
Bottoming / clipping at speed	Raise ride height