Toothmap — free motorcycle gearing instrument. Sprockets, thrust, real tracks.

Bike

Rear tyre

Rolling circumference exact · whether a size clears your rim, swingarm or hugger is not modeled

Toothmap is an interactive instrument and needs JavaScript. The schematic below shows what the bench draws; nothing here tracks you — there is no server to talk to. See how the numbers are made.

The gearing you are setting

Exact ratio math · tooth shape and case layout modeled

Schematic view — crank pinion, clutch basket, the engaged pair, front sprocket, chain, rear sprocket and wheel. The animated bench loads when you look at it and needs JavaScript; every number on this page is the same either way.

Playback only · every ratio and rate is exact at any speed

Front

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Rear

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Gear

Engine

Road speed – · gear – exact

The multiplication

–Primary × –Gear × –Final = –Crank : wheel

Live tallies counted off the drawing. Vs stock is how far the stock sprockets would have carried the bike over the same crank revolutions. Tally since run Crank–rev Wheel–rev Observed–crank : wheel Road–m Wheel rate–rev/s real– Exact · at scene speed

– modeled · 585 mm nominal centres · – nominal

Scene runs at 1/20 speed, a playback choice — every ratio and rate is exact at any of them · past 26 teeth a second a body is drawn as a smooth ring at its pitch diameter, because a tooth row sampled at 60 frames a second reports a direction it is not turning · gearbox and primary spread along their shafts · one pair shown, a real box has six, all constantly meshed · tooth profile and case dimensions modeled · one tooth per sprocket marked so you can watch the ratio · the tally's road distance is the ground the drawing has actually covered, and vs stock compares it over the same crank revolutions

What that means

Final drive –vs stock

Top gear speed / 1000 rpm –

Redline in top –exact ratio math · drag not modeled

Chain –estimated

Speedometer and odometer

Modeled · gearbox-driven speedo assumed

Your change makes it read – pick a bike

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This assumes the speedometer takes its signal from the gearbox output, the usual arrangement on a chain-drive sportbike: it was calibrated for the stock pair and the stock tyre, so changing either makes it wrong. If yours reads off the FRONT wheel, none of this applies — sprockets and rear tyre cannot move it.

This is only the error your change introduces. Whatever optimism the bike left the factory with sits on top of it, and is not modeled here — we hold no per-bike data for it, and inventing a number would be worse than naming the gap.

Speed per gear

Exact ratio math

Thrust at the wheel

Modeled from claimed peaks

On track

Simulated · fixed line · expert pace

Track

Sim class

Saved setups

Saved in this browser only — nothing leaves your phone. A/B: load one setup, then tap COMPARE on another.

Toothmap gearing instrument