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Restore-Stock Ratio Calculator
The one-formula answer to 'what gears do I need for 35s?' — factory ratio corrected for your new tire, with the closest real-world ratios compared.
The restore-stock ratio is the axle ratio that returns factory RPM and feel after a tire size change: factory axle ratio times new tire diameter divided by factory tire diameter.
Formula: restore ratio = factory axle × new tire ÷ factory tire
What this number means
Restore-stock math is the oldest rule in regearing: keep the ratio between tire diameter and axle ratio constant and the truck can't tell anything changed. The table below the headline compares the common ratios you can actually buy — because 3.76 doesn't exist, and the real choice is between 3.73 (2 RPM under factory) and 4.10 (a step deeper), not a decimal.
What to change next
Pick by the RPM column, not the ratio column. Within ~100 RPM of factory at your cruise speed: manners preserved. Consistently 200+ under: expect downshifts and a sluggish feel. 200+ over: you bought trail gearing with highway money — fine if that's the build's honest purpose.
Worked example
Tacoma, factory 3.91 on 30.6-inch tires, going to 33s: restore-stock is 4.22. The table shows 4.30s (the factory manual ratio, widely available) at ~40 RPM over stock manners, and 4.10s ~90 under. Most owners land on 4.30 — the math above shows why.