FFB filters, damping, friction, and smoothness

Every base slider — reconstruction filter, interpolation, damping, friction, inertia, slew rate, smoothing — trades detail for smoothness. That’s the one rule that explains all of them. There are only two ways a wheel feels wrong: notchy/grainy (too sharp, or a mechanical fault) or mushy/numb (too filtered, too weak, or dead in the middle). Almost every fix is moving one slider in the right direction without dragging the rest with it.

The signal chain: where filters live

iRacing runs its tire physics at a 60Hz outer loop and a 360Hz inner loop, then packages six inner-loop samples into each 60Hz FFB packet. Your motor wants thousands of updates a second. So the signal passes through layers, each smoothing the step between one 60Hz number and the next:

sim (60Hz) → interpolation → base reconstruction / smoothing → motor

Filters exist because raw 60Hz packets arrive as steps. Drive a motor straight off those steps and it jumps between torque values — that jump is felt as grain or rattle. Interpolation and reconstruction round the steps into ramps. Turn them up too far and you also round off the real texture you wanted.

The five base sliders, and what each physically does

Damping — resists velocity

Damping applies force proportional to how fast the wheel is turning: spin it quickly, it pushes back harder; hold it still, nothing. It adds weight, slows the wheel, and kills oscillation. In-sim iRacing damping in the 10–55 range is common to stop a shaking wheel; many drivers run around 10 after iRacing’s 360Hz FFB update (native wheel LFE). True Drive Damping 2, VRS 10% are typical light touches. Too much and the wheel feels mushy and laggy.

Friction — constant drag

Friction is resistance independent of speed — static drag, the feel of a mechanical rack. Moza’s go-to is Natural Friction around 5%, True Drive Friction 3. It smooths tiny rattles and adds mechanical weight. Push it up and it numbs the off-center region and hides road texture. Like damping and inertia, it applies constant background torque, so heavy static settings also add constant heat — watch your motor temps if you run a base hot.

Inertia / natural inertia — resists acceleration

Inertia simulates rotating mass: it resists changes in wheel speed, so it dampens fast direction changes and self-oscillation while leaving steady-state detail intact. Moza Natural Inertia at 150% is a popular “weighty but still detailed” setting. It’s not free — raising inertia too far has made CSL DD wheels go notchy and oscillate. Treat it as the feel of a heavier rim.

Reconstruction filter / smoothing / interpolation — re-sample and low-pass

This is the steppiness fix. Simucube’s TrueDrive reconstruction filter re-samples the torque signal and rounds off the step changes between 60Hz packets; values run from 2 (raw) to about 6 (smooth). VRS “Soft 1/2” and Fanatec FEI do the same job at the smoothing layer. iRacing’s 360Hz interpolation toggle (in app.ini) sends all six inner-loop samples instead of one, for smoother ramps; external tools like irFFB and MAIRA re-shape that same signal before it reaches the base. Each costs latency and fine texture. If your wheel rattles, turning the reconstruction filter up — or lowering the slew rate — usually clears it.

Slew rate limit — caps Nm per millisecond

Slew rate caps how fast torque is allowed to change. Limiting it smooths sharp spikes like curb strikes and rattles; unlimited gives the sharpest, most detailed feel. Community-reported figures: Simucube Ultimate around 9.5 Nm/ms, Sport around 4.8 Nm/ms, Mige-based 6–8 Nm/ms. SC2 Pro owners drop slew rate below 0.7 to kill rattling. Lower it and you round off real detail along with the noise.

Fixing notchy / grainy FFB

First diagnose the base. Geared wheels — Logitech G29/G923, Thrustmaster T300/T150 — have physical gear cogging you feel as notches. Software can’t remove it, only mask it with a little friction or smoothing; a belt or direct-drive base is the only real fix. On a DD, notchiness is over-strong texture, too-high inertia, or weak low-force communication. Common culprits:

• Fanatec FEI / Force Effect Intensity too high. At 100 it can feel like grinding through corners; the sweet spot is often around 50.
• Inertia raised too far — back it off until the notch goes.
• Too much road/texture effect in-sim — reduce it before reaching for a base filter.

Fixing mushy / numb / dead-center FFB

Mushy is almost always over-filtering or a weak signal. Back off damping, friction, and smoothing one at a time and feel for the detail returning. Then check clipping: in-sim FFB strength above roughly 75% saturates the signal so peaks flatten into a dull plateau — set strength so the meter rarely pins. The high-end “raw” recipe is no smoothing, no dampers, no filters, unlimited slew rate, 100% in software, in-sim strength around 40–50%, and only a touch of mechanical friction if you need it.

Killing oscillation without killing detail

Oscillation is a latency loop: the motor torque and the sim’s centering spring chase each other, overshooting and correcting. It’s worst with hands off, on straights, in light cars, at low FFB. Keeping a hand on the wheel damps it for free. Beyond that, fix it in order of least detail lost:

1. Small inertia bump
2. Small friction
3. Center / low-speed damping (5–15)
4. Reduce in-sim road texture
5. Lower wheel rotation speed (Simagic “wheel speed” 50–100)

Steering rotation and soft lock

A DD or belt base has no physical lock — the end-stop is software. If base rotation doesn’t match the car’s, you get a mushy rubber end-stop or two soft-locks fighting each other. Best practice: set the base to a high fixed range (900° or 1080°) and let the sim apply each car’s lock. iRacing auto-sets wheel range per car, so a high base value just gets out of the way.

Per-base starting points

• Moza (Pit House): Natural Friction 5%, Natural Inertia 150%, Natural Damping 0.
• Fanatec: FEI around 50.
• Simucube (TrueDrive): reconstruction filter 2–6, slew rate unlimited (lower only to kill rattle).
• VRS: Soft 2, damping 10%.
• iRacing: start with 360Hz interpolation off if you hear noise; in-sim damping around 10.

Tune one slider at a time and you’ll always know which one did what.