Fixie Gears

A street-fixie ratio calculator. Pick a chainring, cog, wheel, and crank; get gear inches, development, gain ratio, speed at cadence, skid patches, and chain-link counts. The URL is the source of truth, so every setup is shareable.

Open the calculator

What it does

• Calculator with live metric cards, cadence table, and skid visualizer
• Optional taped tire circumference and chainstay → even/odd chain links
• Compare up to four setups; explore nearby ratios on a heatmap
• Saved bikes stay in this browser (localStorage); no account
• Metric / imperial and light / dark

All math runs in the browser. There is no backend. After the first visit, the app shell works offline.

Develop

Requires pnpm 11 (standalone script, Homebrew, winget, or Scoop — not Corepack) and Node.js 22.13+.

pnpm install
pnpm dev          # http://localhost:3000
pnpm test
pnpm check        # Biome
pnpm typecheck
pnpm build        # emits dist/client

Lefthook runs Biome on commit and Biome plus typecheck on push.

Stack

Solid 2.0, TanStack Solid Router, Vite, Tailwind 4. Deployed as a static SPA on Netlify (netlify.toml).

Architecture

Client-only SPA. File routes under src/routes/ share one calculator search schema. Domain math is pure TypeScript in src/lib/gear/ with no framework imports. UI is native HTML plus Tailwind wrappers in src/components/ui/. Tests sit next to the code they cover.

Full version: architecture

Domain math

Changing teeth, wheel, or crank recomputes ratio, gear inches, development, gain ratio, speed at cadence, and skid patches in the browser. Optional taped circumference replaces the BSD+2×width diameter estimate. Chainstay lives only in the URL and feeds even/odd chain-link counts — it is not on the drivetrain type.

Full version: domain

State and routing

The bike is the URL search string on every route (v, chainring, cog, wheel, tire, crank, ambi, stay, optional circ). Inputs write through navigate({ search, replace: true }). Derived metrics are memos, never stored. Units and theme are local prefs, not the link.

Full version: state and routing

Decisions

No third-party component or form library. Deploy is Netlify static (dist/client). solid-js and TanStack Solid Router stay on the 2.0 RC line. Package manager is pnpm, not Corepack. The repo is MIT and private so it cannot be published to npm by accident.

Full version: decisions

Contributing

See CONTRIBUTING.md. Agents: AGENTS.md.

License

MIT