Singlespeed riders choose one gear and live with it, so the choice matters: the ratio, the chain length, and whether the wheel sits right in the dropouts with no tensioner. That deserves a proper tool, and a publication with some personality.
- A brand kit covering colour, type, components and voice, with Coggy the mascot, and a site built strictly from it
- A calculator for gear inches, ratio, development, gain ratio, skid patches and chain length, comparing up to three setups
- A magic gear finder: every cog that sits a whole even number of links taut on your chainstay, within ±0.5 mm
- Every setup is a URL you can paste into a forum argument
- An MDX publishing system for field journals, bike checks with spec tables, and gear, with figure, full-bleed, pair and pull-quote components
- Astro 7
- React 19 island
- MDX
- Vitest
- Vercel
- 01
I found a bug in the brief
The chain-length formula in the spec had a factor-of-two error in its last term. The calculator uses exact pitch-circle geometry instead (tangent spans plus the links wrapped on each sprocket) and is unit-tested against the corrected textbook formula.
- 02
Zero JavaScript on articles
The site is static Astro. Only the calculator hydrates, as a single React island. Reading a ride report costs nothing but the photos.
- 03
The brand kit is the source of truth
Tokens live in one stylesheet and components never hard-code a colour. Two grounds per screen, radius no more than 2px, every number in DM Mono. The rules are written down so the next person can keep them.
