Racing Line Lab · Methodology

What the Lab actually computes

By Another One, LLC · every figure in the Lab is a physics-simulation estimate

The Racing Line Lab is a lap simulator, not a lap database. Nothing in it is measured on a real motorcycle: when you move a slider, a physics model re-solves the fastest speed profile the equations allow, on the circuit's real geometry, under the assumptions listed on this page. This page is the honest fine print.

The model

The engine is a quasi-steady-state (QSS) point-mass lap simulation with rigid motorcycle geometry — the classic gg-diagram / speed-profile method used in lap-time analysis, extended with motorcycle-specific constraints. The bike-plus-rider mass sits at a fixed center-of-gravity height on a rigid wheelbase; at every ~3 m station along the racing line the model balances gravity, aerodynamic drag, rolling resistance and tire forces, and sweeps forward and backward along the lap to find the fastest speed profile that never exceeds any limit:

Lateral grip caps cornering speed from the line's curvature (v² = μ_y·g·cosθ / |κ|).
An anisotropic friction ellipse trades longitudinal capacity against lateral demand — you can't brake hard and be at full lean at the same time.
A rear-wheel power cap with idealized gearing limits drive; aerodynamic drag, rolling resistance and grade push back.
Wheelie and stoppie pitch-over caps limit acceleration and braking exactly the way they do on a real bike, and drive is further capped by rear-tire traction.
Grade is modeled (uphill/downhill changes normal load, drive and braking). Banking and crest/dip vertical curvature are not — there is no source data for them at usable resolution, so a corner like a banked bowl reads slower in the Lab than in life.

Deliberately ignored, with reasons: suspension transients (settle in ~0.2–0.4 s, short against the 2–8 s spent in a braking zone or corner), tire slip dynamics (relaxation lengths far below the 3 m station spacing), lean-transient/countersteer dynamics (QSS assumes the bike flicks instantly, which flatters chicanes), gearbox discreteness (ideal gearing), and wind. The full engineering specification behind the model — every equation, constant and limiting-case check — is the same one used for the Apex Track Guides methodology.

The honest design note

The line is precomputed; the speeds are live. The racing line for each track is an approximate minimum-curvature path found offline by a 12,000-sweep optimizer — far too slow to run in a browser. The Lab downloads that fixed line and re-solves only the speed profile on it, live, as you move the sliders. This is the same solver — same equations, same constants — that generated the corner tables in the Track Guides, ported to run in your browser and parity-tested against the original to within 1.5% on every published track. One consequence to know about: the line itself does not change when you change the bike, so a configuration that would really prefer a slightly different line (say, a point-and-shoot line for a liter bike) is mildly underestimated.

What the sliders do

Bike class presets — Supersport 600 (240 kg, 90 kW), liter bike (245 kg, 150 kW), middleweight twin (230 kg, 55 kW); mass figures are bike + rider.
Mass (150–350 kg) and rear-wheel power (40–180 kW) move freely around the presets.
Grip presets map to friction-coefficient pairs (longitudinal μ_x / lateral μ_y): street 0.90/1.00 · sport 1.10/1.20 · slick 1.20/1.30. "Sport" is the pair the validated presets use — warm sport/track-day tires on a dry track.
Held at defaults: CG height 0.60 m, wheelbase 1.44 m, 50/50 static weight split, drag area CdA 0.32 m² (rider tucked), air density 1.225 kg/m³, rolling resistance 0.015.

Assumptions, verbatim

These ship inside every track pack the Lab downloads:

Quasi-steady-state point-mass motorcycle simulation on an approximate minimum-curvature racing line held within the track corridor.
The racing line is precomputed offline (12,000-sweep coordinate-descent optimizer); the browser engine re-solves only the speed profile on this fixed line.
Anisotropic friction ellipse μ_x=1.10 / μ_y=1.20 for the stock presets (warm sport/trackday tires, dry track).
Rear-wheel power cap with ideal gearing; aerodynamic drag CdA=0.32 m², ρ=1.225 kg/m³, C_rr=0.015.
Wheelie and stoppie pitch-over caps included (CG h=0.60 m, wheelbase 1.44 m, 50/50 static split); rear-traction cap included.
Grade (uphill/downhill) affects normal load, drive, and braking; banking and crest/dip vertical-curvature effects omitted (no source data at usable resolution).
Track geometry resampled to ~3 m stations; curvature from smoothed three-point circumcircle fit.
All numbers are simulation estimates for an idealized fast rider, not measured data.

Read this before trusting any number

The model is an idealized fast rider. It uses all the grip, all the time, and never makes a mistake. Real riders — fast ones included — leave margin. Treat every figure as a geometry-shaped ceiling, not a target.
The geometry is approximate. Track outlines come from OpenStreetMap and elevation from public terrain data; curbs, camber, banking and surface changes are invisible to the model.
Your day will differ. Wind, temperature, tires, traffic and skill move real speeds substantially; the simulation knows none of it.

Disclaimer

Every speed, time and distance in the Racing Line Lab is a physics-simulation estimate computed from track geometry under the stated assumptions. It is reference data — not riding instruction. Always ride within your limits and follow your track organization's instructions.

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