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Gear Ratio vs Tire Size Chart — the Restore-Stock Multiplier
One multiplier runs every regear: new tire ÷ factory tire. Multiply your factory axle ratio by it and you have the ratio that restores factory RPM and feel. This page is that table, for every common tire jump — then the platform pages take it the rest of the way.
| Factory tire ↓ · New tire → | 31 in | 32 in | 33 in | 34 in | 35 in | 37 in | 39 in | 40 in |
|---|---|---|---|---|---|---|---|---|
| 28 in | ×1.107 | ×1.143 | ×1.179 | ×1.214 | ×1.250 | ×1.321 | ×1.393 | ×1.429 |
| 29 in | ×1.069 | ×1.103 | ×1.138 | ×1.172 | ×1.207 | ×1.276 | ×1.345 | ×1.379 |
| 30 in | ×1.033 | ×1.067 | ×1.100 | ×1.133 | ×1.167 | ×1.233 | ×1.300 | ×1.333 |
| 31 in | ×1.000 | ×1.032 | ×1.065 | ×1.097 | ×1.129 | ×1.194 | ×1.258 | ×1.290 |
| 32 in | ×0.969 | ×1.000 | ×1.031 | ×1.062 | ×1.094 | ×1.156 | ×1.219 | ×1.250 |
| 33 in | ×0.939 | ×0.970 | ×1.000 | ×1.030 | ×1.061 | ×1.121 | ×1.182 | ×1.212 |
How to use it
Find your factory tire diameter on the left (use the tire diameter calculator if the sidewall is metric), your planned tire across the top, and multiply. A JL Sport (3.45 gears, 31.5-inch tires) going to 35s: ×1.111 → 3.83 restore-stock, so the real-world choice is 3.73 (a hair under) or 4.10 (one step deeper). The multiplier works because gearing and tire diameter trade linearly — double-check any result in the restore-stock calculator.
Platform charts
The multiplier is universal; the transmissions and transfer cases are not. For crawl ratios and cruise RPM with your platform's actual gearbox, use the verified platform charts: