RC Gear Ratio Chart Maker
Build a printable pinion & spur chart for any class. Set your own ranges and toggle between gear ratio, FDR, and rollout (mm).
Want to compare two specific gearings side-by-side? Use the gear ratio calculator.
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Off-road racers usually think in gear ratio (spur ÷ pinion).
Loading a preset fills the values for that class — tweak from there to match your car.
Chasing the right ratio?
Shop pinions, spurs & tires at AMain →
Gear ratio by pinion & spur
Gear ratio = spur / pinion (no internal multiplication). Off-road racers typically think in this number. Cells are shaded relative to your current setup — green for combos with less motor load (taller gearing), red for more motor load (shorter gearing, more top speed).
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| 77T | 78T | 79T | 80T | 81T | 82T | 83T | |
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Want to compare your current vs new gearing side-by-side?
The gear ratio calculator shows the percentage change between two specific setups — useful for quick gearing swaps between rounds.
Open RC Gear Ratio Calculator →How to read this chart
- • Gear ratio = spur ÷ pinion. Just the visible gear math, no diff reduction. Off-road racers typically think in this number.
- • FDR (final drive ratio) = gear ratio × internal ratio. Touring and drift racers typically think in FDR.
- • Rollout = π × tire diameter ÷ FDR. Distance per motor revolution. Foam-tire racers (1/12 pan, on-road carpet) think in rollout because tire diameter shrinks during a heat.
- • Internal ratio is your car's gearbox reduction past the spur — off-road buggies are typically 2.4–2.6:1, touring/drift 1.9:1, 1/12 pan 1.0 (direct drive). Use the car search to auto-fill it for any supported model.
- • Cells are colored relative to the chart range, not an absolute scale.
- • Click any cell to set your pinion and spur centers. Your inputs are saved in this browser for next visit.
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Setup App & Race Log
Got your rollout dialed? Track the whole setup.
The RC Setup App saves your settings for 600+ cars, has this gear calculator built in, and gives personalized AI tuning answers for your exact car — at the track or back in the pits.
- Gear Ratio Calculator
- AI Mechanic answers
- Setup Tracking
- Find & Share Setups
- Race Log
- Free to use
Just want the calculators?
Pit Calc Pro is our free standalone calculator app for iOS & Android.