Jeep Tire Size & Regear Calculator
See what bigger tires do to your highway RPM and speedometer, and which axle ratio brings back stock feel. Runs entirely in your browser.
How the math works
- RPM = MPH × axle ratio × top-gear ratio × 336 ÷ tire diameter (inches).
- Regear to restore stock feel = stock ratio × new tire ÷ stock tire, rounded to a ratio you can actually buy.
- Speedo error: actual speed = indicated × new tire ÷ stock tire, until you recalibrate with a programmer.
Real tires run a little smaller than their label (tread depth, load, air pressure), so treat results as close estimates. Many Rubicons ship with 4.10 gears; check your axle tag or build sheet.
Disclaimer: Estimates only, not a mechanic’s sign-off. Verify gear ratios, tire clearance and load ratings for your exact year, trim and doors before buying parts.