Every minimoto paddock has a gearing expert. He knows what everyone is running, he changed two teeth last round and gained half a second, and he will tell you the number. Do not write the number down. Gearing is a decision, and like every decision on a race bike it belongs to the rider, the track, and the corner where the time is actually being lost — not to the loudest voice in the pit lane.
Use the track you know
Shannonville — the proving ground our track guide covers — is the perfect classroom because its character is extreme: long straights where the fast bikes stretch out, and heavy-braking corners and hairpin sections that punish a bike geared wrong in either direction. That is the whole gearing problem in one venue. Gear tall and the straights feel glorious while the bike falls out of its power arriving at the tight stuff. Gear short and the hairpins launch beautifully while the straight turns into a parade. A track with only fast corners or only slow ones barely poses the question. A track with both asks it on every lap.
What a tooth actually changes
The mental model, in plain terms: the relationship between one tooth on the front and teeth on the rear is a ratio, and the ratio trades acceleration against top speed — nothing else. A change at the countershaft is a big step for small money and effort; a change at the rear is a smaller step. There is no universally correct setting, which is the entire point: gearing is choosing which corners you want to help, at the cost of which others. And the bike will tell you if you listen: an engine that screams past its useful revs halfway down the straight is asking for a taller ratio; an engine that never reaches its happy place before braking is begging for a shorter one.
Find where the rider is losing
The method beats the magic number. Watch the sessions — trackside, not from a chair — and find where your rider is actually losing time. Passing everyone on the straight and losing it all back into turn one is not a gearing problem; it is a braking problem, and no tooth will fix it. Getting munched down the straight while carrying better corner speed is. Match the gearing change to the observed weakness, make one change at a time, and let lap times — not opinions — confirm or veto it. Timing data over feelings, the same discipline our transponders post keeps preaching.
The Shannonville worked example
Run the exercise on the track we all share: note where the revs run out (or never arrive) down the long straight, note how the bike launches off the hairpins, change one ratio step, and go see what the clock says. Then write down what you did — the gear, the weather, the result — because gearing knowledge compounds only if it is written somewhere the paddock expert cannot overwrite it. Gearing is a decision, not a rumour. Make it with your rider's eyes and your own stopwatch, and you will make it again next round with better information.