Regear Calculator

Bigger tires quietly change how the vehicle drives — softer acceleration, lower highway RPM, less towing punch — because the axle now turns fewer times per mile. Enter your factory ratio and tire sizes to see exactly what axle ratio restores the stock feel, and the closest ratio a gear-set maker actually sells.

Factory axle ratio

Factory (old) tire

New tire

This finds the ratio that restores the stock RPM-per-mph relationship — not every gear set exists for every axle, and some vehicles can't be regeared at all (sealed unibody axles, some AWD/EV drive units). Confirm exact availability with a gear-set maker (Randy's Ring & Pinion, Nitro Gear, USA Standard) or your differential's part number before ordering.

Why regearing restores the feel

A bigger tire acts like a numerically lower (taller) axle ratio — fewer axle turns per mile means less torque multiplication and lower RPM at any given speed. Installing a numerically higher (shorter) ratio in the differential exactly cancels that out: same RPM at the same road speed, same torque multiplication, same acceleration feel as the factory tire and gear combination.

Ratios aren't sold in arbitrary decimals — gear-set makers cut a fixed catalog (2.73, 3.55, 3.73, 3.90, 4.10, 4.56…), so the right move is usually the closest ratio actually stocked, not the exact mathematical target.

When regearing is worth it

Under about 3% diameter change — not worth the cost of a gear swap; the drivetrain barely notices.
3–7% — a real change in feel and highway RPM. Worth regearing if you tow, or if you're keeping the tire size long-term.
Over 7% (most 35"+ tire swaps on a stock-diameter truck) — regearing is close to mandatory for towing, and strongly recommended even for daily driving. This is exactly why lifted trucks running 35s or 37s are almost always regeared.

See the ratio change without regearing →
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