MotoTunerBlog · 21 Aug 2026 · 8 min
Motorcycle gearing — RPM at the end of the straight
Straightaway RPM is engine speed at a chosen road speed in a chosen gear, given the sprockets you actually have and the tire you will race. It is not “it felt busy.” One tooth on the rear is a few hundred rpm at the same km/h — enough to put you on the limiter before the board, or leave you short of the power peak when you need to pass.
Measure, don’t trust last year’s sheet
- Count front and rear sprocket teeth.
- Measure loaded rolling circumference on the race tire: mark, one wheel revolution, rider aboard or the bike on the ground. Sidewall diameter is not circumference.
- Confirm primary ratio from the manual (typical 600/1000 sportbike ≈ 1.7–1.9).
- Confirm the gearbox ratio for the gear you finish the straight in (6th is often ~1.15).
- Use the speed you actually see (GPS or dash).
The identity
rpm = (kph / 3.6) / (circ_mm / 1000) × 60 × (rear / front) × primary × gearbox
MotoTuner reports rpm. Limiter vs power-peak is your choice. A 190/55 that grew 3% at 250 km/h is a different motorcycle than the 1995 mm you rolled in the paddock — write the tire with the session.
Why this belongs on the pit board
Guessing a tooth and discovering it on the last lap of qualifying is how club days get expensive. Put gearing on the same setup sheet as sag and clickers. Change one thing. See if the board still arrives at the rpm you wanted.
MotoTuner is a pit-board app, not a race engineer. Calculators are handbook rules of thumb. You own how the motorcycle is set.