Bike Calc

Two tools that share one bike catalog:

• Gear calculator (/): gear inches, meters development and speed for every chainring × sprocket (or hub gear), with a to-scale side drawing of the bike. The chain sits on the selected gear; cranks turn at the cadence and wheels at cadence × gear ratio.
• Fit visualizer (/fit): compare hand, saddle and toe positions across bikes, stems and bars, drawn from the side and from above. Settings are saved in the browser.

Development

Requires Node 22.22 or newer.

npm install
npm run dev        # dev server
npm run build      # static site in build/client
npm run preview    # serve build/client locally
npm run typecheck
npm run lint

Stack

React Router 8 in framework mode on Vite, with ssr: false and prerender: true (react-router.config.ts). Every route is rendered to static HTML at build time, so there is no server: deploy build/client to any static host. vercel.json sets this up on Vercel. Paths with no page get 404.html, which hydrates into the app's not-found page.

Styling is plain CSS with design tokens in app/app.css, including dark mode. The searchable selects use Radix Popover and cmdk.

Layout

app/                 root layout, routes, styles
components/board/    drafting board, mm grid, frame and wheel drawing shared by both tools
components/gears/    gear calculator: sidebar, heat-map table, drivetrain drawing
components/fit/      fit visualizer: bike cards, readouts, side and top views
lib/data/            catalog: tires, cassettes, bikes, stems and bars
lib/gears.ts         gear maths
lib/fit/             fit solver, saved settings, sidebar layout
lib/frame.ts         frame key points from stack, reach and angles

Data

The catalog is a set of typed static modules in lib/data/.

• A bike in bikes.ts can have a drivetrain, a geometry, or both. With a drivetrain it appears in the gear calculator. With geometry it appears in the fit visualizer, and the gear calculator draws its real frame instead of the reference frame.
• Hub ratios in cassettes.ts are hub output speed over sprocket speed, gear 1 first, so 1.0 is direct drive.
• Stem and bar keys in cockpit.ts are stored in saved fit settings. Rename one only with a migration in lib/fit/state.ts.
• Missing tires, cassettes and bikes can be suggested through the Google Forms in lib/forms.ts.