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Piyush Verma
DEFIANZ / ENGINEERING NOTES / 05

Tire dynamics. Grip & load transfer.

Fit a tire curve to synthetic measurements, then explore the load transfer that changes how much each axle can do.

25 SYNTHETIC SAMPLES / SEED 16
LATERAL TIRE FORCEPARAMETRIC MODEL + SYNTHETIC DATA
-900-4500450900-15°-10°-5°0°5°10°15°Fy / NSlip angle α
Synthetic noisy measurementsCurrent model
Lateral force Fy550 N
Peak scale μFz900 N
Fit RMSE154.4 N
Samples25
A REDUCED MAGIC FORMULA

Linear at first.
Then it saturates.

Fy = D sin(C atan(Bα − E(Bα − atan Bα)))

D = μFz. The synthetic data uses B = 10, C = 1.4 and E = −0.5 with deterministic noise. These are invented demonstration parameters, not regression coefficients from team tire data.

BRAKING / QUASI-STATIC LOAD TRANSFER

The load moves forward.

For an illustrative 300 kg car with driver, a 2.06 m wheelbase and 48% static front weight, braking transfers ΔF = m a h / L from the rear axle to the front.

Deceleration4 m/s²
CG height0.3 m
FRONT AXLE LOAD1587 N
REAR AXLE LOAD1356 N

Requested deceleration is below the μg ceiling of this simple flat-road model.

WHY THE CONTROLLER CARES

One contact patch.
A shared force budget.

Braking and cornering compete for the same tire grip. This simplified circle shows the total-force limit Fx² + Fy² ≤ (μFz)². Real tires have load sensitivity and a more complicated combined-slip envelope.

FxFyAMBER / REQUESTED BRAKING FORCETry reducing the controller’s grip ceiling ↗
UNDER THE HOOD

What you’re seeing.

My work: MATLAB multibody simulation with a tire model derived by regression from tire data. The original dataset and coefficients are not available in this portfolio. This experiment uses synthetic measurements to show the fitting process.

Limits: the displayed lateral curve assumes pure slip, constant load and no camber or temperature effects. The load-transfer calculation is quasi-static and ignores suspension pitch, aerodynamics and road inclination. A low residual on synthetic data validates the fit to this dataset, not a real tire.

Educational reconstructions of ideas from my work. Demo results are computed here; they are not team test results.