Tractor lead/lag calculator
Changing tires on an MFWD tractor? Pick your current and new sizes — we show how the front axle lead changes. No gear ratio needed.
Your current tires (the ones that work)
New tires you are considering
I know my tractor's gear ratio — show the exact lead %
The inter-axle ratio (how many turns the front wheels make per turn of the rears) is in the operator's manual or from the dealer. Typical MFWD tractors: 1.2–1.5.
How to read the result
- Lead = how much faster the front tires travel than the rears. +1% to +5% is the usual working range, around +2.5% is a common target.
- Change vs current tires: if your current setup works well, keep the change within about ±1 percentage point. A bigger change can cause driveline wind-up, fast front tire wear or poor steering.
- Below 0% (lag) or above +6% is a problem in any case.
- Formula: lead % = (front rolling circumference × gear ratio ÷ rear rolling circumference − 1) × 100.
- Always confirm with the tractor maker's list of approved tire combinations.
Rolling circumference: Continental Agricultural Tires Technical Databook (values calculated by Continental) and the Firestone Ag data book Rolling Circumference Index chart (approximate per group). Real values differ slightly between brands, tread depth and pressure. Method: K&M Tire “Calculating Lead/Lag”, CEAT Specialty. Data checked October 2026.