Mastering Our Gearbox Ratio Calculator : Step-by-Step

Selecting the perfect gearing setup is a balancing act between torque and top speed. Our Kotouč Gearboxes Calculator shows the trade-offs clearly so you can tailor your build with confidence.

1) Start with Your Final Drive

Enter the Crown wheel and Pinion shaft tooth counts. The calculator computes the final-drive ratio (crown ÷ pinion). This single number heavily influences acceleration vs. top-speed feel.

Exploring hardware options? See our latest gearbox updates in STILL SHIFTING AHEAD: What’s New 2024–2026.

2) Define Your Tyre Size

Provide either the tyre circumference (cm) or the standard width / aspect / rim. The calculator uses this to convert engine RPM into vehicle speed per gear.

Want stronger, smoother parts? Learn why we build Isotropic Superfinishing into our gearboxes.

3) Set Your Maximum RPM

Enter your engine’s Max RPM. This defines the top-of-rev calculation point so the tool can estimate speed in each gear at your redline.

4) Add Tooth Counts for Each Gear

For gears 1–8, fill in Tooth In (input) and Tooth Out (output). The calculator derives each gear ratio automatically and uses it with the final drive and tyre size to compute road speed.

Looking for interruption-free upshifts? Read our explainer on Seamless Shifting.

5) Read the Results & Graph

• Per-gear ratio and speed at Max RPM.
• RPM drop between shifts to see how tightly your stack holds the engine in the power band.
• Optional comparison for Final drive 1/2 to preview how a different diff ratio changes speeds and drops.
• A Ratio graph to visualise spacing; use the Print/Save button to export your setup.

6) Experiment & Fine-Tune

Try taller or shorter final drives and adjust gear teeth until your speeds and RPM drops match the track. Pair your gearing with our Universal AWD Controller to tune torque split and response for surface and weather.

Tip: Save multiple setups (different final drives or tyre sizes) and compare printed sheets in the pits to pick your gearing for the day.