km/h
mm
Result
Engine speed3,993 rpm
How it is calculated, with your numbers
- Overall reduction
overall = primary × gear × rear / front1.652 × 0.857 × 45 / 15 = 4.247 - Wheel speed
wheel = speed × 1000000 / 60 / circ110 × 1000000 / 60 / 1,950 = 940 rpm - Engine speed
rpm = wheel × overall940.171 × 4.24729 = 3,993 rpm
Working uses the metric units the formula is written in.
- speed Road speed (km/h)
- primary Primary reduction ratio
- gear Gear ratio
- front Front sprocket or pulley teeth
- rear Rear sprocket or pulley teeth
- circ Rear tyre rolling circumference (mm)
- overall Overall reduction
- wheel Wheel speed
- rpm Engine speed
What it means
The reverse of the road speed calculator: turn the road speed into wheel revolutions per minute, then multiply by the overall reduction to get engine rpm. Useful for choosing gearing for long motorway days, or for checking whether a sprocket or pulley change puts you in a vibration band at your usual cruising speed.
Assumptions and limits
- No slip; use the measured rolling circumference.
Sources
- Foale, T., Motorcycle Handling and Chassis Design: The Art and Science, 2002.