Joker Chains

Joker Chains is an offline-first motorcycle drivetrain care card for riders who maintain one named bike chain at a time. Open the app and land on a fullscreen chain-sag surface: a clear side-view drive chain between front and rear sprockets, with a large millimetre sag ruler, target band highlight, and color cues when slack is over or under for the active bike. Log what actually matters on the road and in the garage. Enter typed slack in mm, count left and right axle-adjuster clicks, and watch the diagram and adjustment history update together. Stamp odometer readings (trip and lifetime, miles or km) so the card can derive distance since last lube, last clean, last adjust, and last sprocket change—without guesswork. Record lube and clean events with product and notes fields. A distance-per-lube trend chip on the main card shows how your interval is holding. When you swap sprockets or chain, register tooth counts, brand or type, and install odometer; the life estimate resets while prior sets stay in history. An estimated chain-life percentage—built from cumulative miles, adjustment frequency, and your own service limits—appears as a ring on the drivetrain card so the next decision is obvious at a glance: lube, tighten, or replace. Local notifications fire from your DataStore thresholds (lube miles, max sag mm). No location tracking and no sensors required. Keep a multi-bike garage: each bike has its own chain card, units (mm/in, mi/km), and target slack range. A seed demo bike is ready on first launch so you can explore before adding your own. Browse a filterable timeline of lubes, cleans, adjusts, and part swaps, then export a plain-text service sheet when you need a record. A home-screen widget shows active bike name, last slack mm, life %, and miles since lube. Built for riders who want one focused drivetrain card—not a bloated garage suite. Measure slack, log miles, and know exactly when to service the chain.