Apex Track Guides · Methodology

How the numbers are computed

Generated 2026-10-02 · by Another One LLC

Every speed, brake point and lap time in these guides is the output of a physics simulation — not a measurement, not a recorded lap, and not anyone's opinion of how a corner should be ridden. This page explains exactly what the model is, what it assumes, where it's weak, and how we sanity-check it before publishing a track.

The model

The simulator is a quasi-steady-state point-mass lap simulation — the industry-standard “gg-diagram / speed-profile” method used in lap-time analysis, extended with motorcycle-specific constraints. The bike is treated as a point mass 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 finds the fastest speed profile the tires and engine allow:

• Tires obey an anisotropic friction ellipse — independent longitudinal and lateral grip limits that trade off against each other when braking or driving while leaned over.
• A rear-wheel power cap with idealized gearing limits acceleration; aerodynamic drag and rolling resistance push back.
• Wheelie and stoppie pitch-over limits cap acceleration and braking the way they do on a real motorcycle, and drive is limited by rear-tire traction.
• Grade matters: uphill and downhill sections change normal load, drive and braking. Banking and crest/dip effects are not modeled — there is no source data for them at usable resolution.

The reference line itself is solved as a minimum-lap-time optimal-control problem — a 1000 cc motorcycle ridden to a club-rider envelope on the bike layout's mapped geometry, with standard track-riding technique (braking done early, one steering input per corner, throttle rolled on once the bike is set) — held within the track corridor. The corner metrics (effective radius, arc length, elevation delta) are measured from that line and the surveyed elevation profile. It is a starting reference, not the only way around.

The three bike-class presets

Corner tables on the site show the Supersport 600 preset; the downloadable pack includes all three classes for every corner. Mass figures are bike plus rider.

Preset	Mass	Rear-wheel power	μ long.	μ lat.
Supersport 600	240 kg	90 kW (121 hp)	1.10	1.20
Liter bike (1000cc superbike)	245 kg	150 kW (201 hp)	1.10	1.20
Middleweight twin (650)	230 kg	55 kW (74 hp)	1.10	1.20

All classes share warm sport/track-day tire grip (dry track), drag area C_dA = 0.32 m² (rider tucked), air density 1.225 kg/m³, rolling resistance 0.015, CG height 0.60 m, wheelbase 1.44 m, 50/50 static weight split.

Assumptions, verbatim

These ship with every track's data file:

• Reference line: apex-sim minimum-lap-time optimal control of a motorcycle (1000 cc, club-rider envelope) on the layout's measured geometry, held within the track corridor.
• Rider technique follows standard track-riding practice: braking done early and tapering off by ~25° of lean, one steering input per corner, throttle rolled on once the bike is set.
• The browser engine re-solves only the speed profile on this fixed line for the selected bike class.
• Anisotropic friction ellipse mu_x=1.10 / mu_y=1.20 (warm sport/trackday tires, dry track).
• Rear-wheel power cap with ideal gearing; aerodynamic drag CdA=0.32 m^2 (tucked), rho=1.225 kg/m^3, Crr=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.
• All numbers are simulation estimates, not measured data — a starting reference, not riding instruction.

Known limits — read this part

• The model is an idealized fast rider. It flicks the bike instantly, never misses an apex, and uses all the grip all the time. Real riders — including fast ones — leave margin. Treat the numbers as a ceiling shaped by geometry, not a target.
• Corridor and elevation data are approximate. Track outlines come from OpenStreetMap and elevation from public terrain data; curbs, camber, banking and surface changes are invisible to the model.
• Chicanes and flick transitions flatter the sim. Quasi-steady-state modeling assumes lean angle changes instantly, so very fast direction changes read a little quicker than reality.
• No two days are alike. Wind, temperature, tires, traffic and rider skill move real speeds substantially. The simulation knows none of that.

The sanity gate

Before a track is published we compare the simulated liter-bike lap against a published motorcycle reference lap for the same configuration where one exists. The criterion: pass = sim liter-bike lap within [0.85, 1.45] of the configuration-matched published motorcycle reference; tracks with no such reference pass if average lap speed is 90-190 km/h (the line is corridor-bounded by construction) A slightly slow simulated lap is expected — lap records are set by professional racers on racing slicks; the model runs track-day tire grip. Tracks that fail are not published: of 46 simulated tracks, 46 passed.

Reference laps are cited as published by their sources (MotoAmerica, Roadracing World, club racing organizations). They are used only as an order-of-magnitude check on the simulation — no affiliation or endorsement is implied.

Disclaimer

Track outline data: Track outline © OpenStreetMap contributors (ODbL). Elevation from public terrain data. Guides © 2026 Another One LLC · hey@apexlines.app