Methodology

GIIRR uses standard geometry and kinematics rather than proprietary vehicle data.

Ratios

For a simple driven/driver pair, GIIRR uses driven ÷ driver as the numerical reduction ratio. Output RPM is input RPM divided by that ratio.

Road speed

Wheel speed is converted to linear speed through tire circumference. Nominal tire-size calculations use the geometric sidewall formula; they do not model loaded radius.

Losses

Where efficiency is requested, the entered percentage is applied as a multiplier. GIIRR does not invent efficiency values for you.

Rounding

Displayed values are rounded for readability. Display precision is not measurement accuracy.

Quality control

Core formulas are regression-tested before deployment. For safety, legality or component selection, verify results against manufacturer documentation and physical measurements.