Bike Split EstimatorTaper · Prototype

GPX course · steady target power · race-day forecast wind. An honest estimate, not a promise.

01 Course GPX track or route file — the same file you'd feed BBS

Drop your GPX here

or click to browse · elevation data required for climbing maths

—

Distance km

—

Gain m

—

Loss m

—

Segments

—

Start lat, lon

02 Rider & bike

Rider weight kg Bike + kit kg FTP watts Target power watts Position / CdA average Known CdA m² · overrides preset Road surface / Crr Dead turns / U-turns count Time cost per turn sec

Target power is ridden as a steady effort (VI ≈ 1.0). IF shows live below the button. CdA presets are honest ballparks — if you've got a tested or BBS-calibrated number, put it in Known CdA and it takes over. Leave it blank to use the preset.

03 Race-day conditions

Pull forecast (Open-Meteo) Set manually

Race date Bike start time local

Forecast covers ~16 days ahead. Beyond that, or with no internet, flick to manual — the maths is identical, only the inputs change. Wind is applied per segment using the course bearing, and shifts hour-by-hour as your predicted ride progresses.

Predicted bike split

—:—:—

—

Avg km/h

—

Power W (steady)

—

TSS

—

Work kJ

—

W/kg

—

Honest range

Elevation Predicted speed (grey → pink = slow → fast)

Km	Grade %	Wind m/s	Speed km/h	Split	Elapsed

Where this model is honest — and where it isn't

What it does: full physics forward model (aero drag, rolling resistance, gravity, drivetrain loss) solved per course segment from your GPX, with per-segment wind from the forecast bearing and hour-shifted conditions as the ride progresses. Validated within ~1% of Best Bike Split on flat steady courses (Busselton IM).

What it doesn't do: no variable-power optimisation (BBS solves for the fastest power distribution; this rides steady power, so expect it to run slightly quick on hilly or surging courses). No cornering or braking model beyond the dead-turn penalty — technical courses will run faster here than in real life. CdA and Crr are presets unless you've tested; a wrong CdA moves the answer more than anything else on this page.

The rule: treat the range, not the number. This is a sanity-check and pacing anchor — race-day execution still comes from your MP race plan.