About this project

The original cycle-ergo.com is the definitive tool for visualizing rider fit on a motorcycle, and it has been for over a decade. It hasn't received updates in years — newer bikes are missing, the UI is tied to a desktop-only layout, and there's no way to share a comparison or save your profile.

This rebuild keeps what worked (the “rider triangle” idea, easy parameter tweaks, multi-bike comparison) and modernizes the rest: mobile-first responsive layout, real-time interactive 2D today and 3D coming, shareable URLs, user accounts, and a catalog that grows with community contributions.

The catalog is built in layers, each more authoritative than the last:

1. Seed reference (private): we use cycle-ergo's catalog to learn which bikes to include. Their inline HTML lists ~1,350 models across ~65 manufacturers with year ranges. We don't republish their compilation; it just tells us what to chase.
2. Manufacturer spec sheets: for every bike, we scrape the OEM page for the public technical data — seat height, wheelbase, weight, wheel sizes. These are published facts. Source URLs are recorded with each measurement.
3. Computer-vision estimation: the precise position of handlebars, seat contact point, and pegs isn't in spec sheets. We extract these from side-profile press photos using the known wheel diameter as a scale reference.
4. Community verification: riders can submit measurements and corrections with photos. Two independent submissions agreeing within tolerance promote a bike to verified.

Each bike's detail page shows its current data source. Bikes seeded from cycle-ergo without OEM verification are marked cycle-ergo-seed; you should treat numbers there as provisional.

Your body is treated as a chain of segments — thigh, shank, torso, upper arm, forearm — whose lengths are derived from your height and inseam using standard anthropometric ratios (Drillis–Contini). The simulator places your hands at the handlebars and feet at the pegs, then uses inverse kinematics to solve for the rest of your pose.

The numbers reported next to the side view — knee angle, hip angle, elbow angle, torso lean — are the actual interior joint angles from that solve. They're classified by rough thresholds (a “cramped” knee, a “sporty” elbow, etc.) so you can compare bikes at a glance.

Some caveats: the model is 2D side-view only (3D comes in Phase 2), seat-position bias and arm straightness are approximations, and we don't yet model lean angle, body weight distribution, or rider gear.

Until you create an account, everything you enter — height, inseam, adjustments — is stored in your browser's localStorage and encoded into the page URL. We don't send any of it to a server. Shareable links contain your numbers; if that bothers you, don't share the link.

If a bike's measurements feel wrong — your knees are crammed where they shouldn't be, or the bars are unreachable when you know they aren't — please tell us. A correction form is now available on bike detail pages for signed-in riders, and submitted fixes go through an admin queue before they affect the simulator.