Whenever you change tire size, there will be a direct effect on power and driveability. The chart below will assist you in finding your new gear ratio needed to give you optimal performance. This chart is based on a drivetrain running at a 1:1 gear ratio at 65 MPH using a manual transmission, meaning the transmission and transfer case are passing power through from the engine at a 1:1 ratio without any overdrive or reduction before it reaches the differential. Automatic transmissions will run at a slightly higher RPM and applications with an overdrive transmission will run with slightly lower engine RPM. | |||||||||||||||||||||
First locate your current gear ratio and tire diameter and then find your approximate RPM at 65 MPH, then reference your new tire diameter with your desired RPM to find the new gear ratio needed. Axle Ratio = (RPM X Tire Size)/(Speed(MPH) X 336) Example 4.88 = (2881 X 37)/(65 X 336) |
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Most Power, Best for Towing, Reduced Fuel Economy | |||||||||||||||||||||
Daily Driver, Best Overall Performance | |||||||||||||||||||||
Highway Driving, Good Fuel Economy | |||||||||||||||||||||
Gear Ratio | |||||||||||||||||||||
2.73 | 2.94 | 3.07 | 3.21 | 3.31 | 3.42 | 3.55 | 3.73 | 3.91 | 4.11 | 4.27 | 4.56 | 4.88 | 5.13 | 5.29 | 5.38 | 5.71 | 6.17 | ||||
25" | 2385 | 2568 | 2682 | 2804 | 2892 | 2988 | 3101 | 3259 | 3416 | 3590 | 3730 | 3984 | 4263 | 4482 | 4621 | 4700 | 4988 | 5390 | |||
26" | 2293 | 2470 | 2579 | 2696 | 2780 | 2873 | 2982 | 3133 | 3284 | 3452 | 3587 | 3830 | 4099 | 4309 | 4444 | 4519 | 4796 | 5183 | |||
27" | 2208 | 2378 | 2483 | 2597 | 2677 | 2766 | 2872 | 3017 | 3163 | 3325 | 3454 | 3689 | 3947 | 4150 | 4279 | 4352 | 4619 | 4991 | |||
28" | 2129 | 2293 | 2395 | 2504 | 2582 | 2668 | 2769 | 2909 | 3050 | 3206 | 3331 | 3557 | 3806 | 4001 | 4126 | 4196 | 4454 | 4813 | |||
29" | 2056 | 2214 | 2312 | 2417 | 2493 | 2576 | 2674 | 2809 | 2945 | 3095 | 3216 | 3434 | 3675 | 3863 | 3984 | 4052 | 4300 | 4647 | |||
30" | 1987 | 2140 | 2235 | 2337 | 2410 | 2490 | 2584 | 2715 | 2846 | 2992 | 3109 | 3320 | 3553 | 3735 | 3851 | 3917 | 4157 | 4492 | |||
31" | 1923 | 2071 | 2163 | 2261 | 2332 | 2409 | 2501 | 2628 | 2755 | 2896 | 3008 | 3213 | 3438 | 3614 | 3727 | 3790 | 4023 | 4347 | |||
32" | 1863 | 2007 | 2095 | 2191 | 2259 | 2334 | 2423 | 2546 | 2669 | 2805 | 2914 | 3112 | 3331 | 3501 | 3610 | 3672 | 3897 | 4211 | |||
33" | 1807 | 1946 | 2032 | 2124 | 2191 | 2263 | 2349 | 2469 | 2588 | 2720 | 2826 | 3018 | 3230 | 3395 | 3501 | 3561 | 3779 | 4083 | |||
34" | 1754 | 1889 | 1972 | 2062 | 2126 | 2197 | 2280 | 2396 | 2512 | 2640 | 2743 | 2929 | 3135 | 3295 | 3398 | 3456 | 3668 | 3963 | |||
35" | 1704 | 1835 | 1916 | 2003 | 2065 | 2134 | 2215 | 2328 | 2440 | 2565 | 2664 | 2845 | 3045 | 3201 | 3301 | 3357 | 3563 | 3850 | |||
36" | 1656 | 1784 | 1862 | 1947 | 2008 | 2075 | 2154 | 2263 | 2372 | 2493 | 2590 | 2766 | 2961 | 3112 | 3209 | 3264 | 3464 | 3743 | |||
37" | 1611 | 1735 | 1812 | 1895 | 1954 | 2019 | 2095 | 2202 | 2308 | 2426 | 2520 | 2692 | 2881 | 3028 | 3123 | 3176 | 3370 | 3642 | |||
38" | 1569 | 1690 | 1764 | 1845 | 1902 | 1966 | 2040 | 2144 | 2247 | 2362 | 2454 | 2621 | 2805 | 2948 | 3040 | 3092 | 3282 | 3546 | |||
39" | 1529 | 1646 | 1719 | 1798 | 1854 | 1915 | 1988 | 2089 | 2190 | 2302 | 2391 | 2554 | 2733 | 2873 | 2962 | 3013 | 3198 | 3455 | |||
40" | 1491 | 1605 | 1676 | 1753 | 1807 | 1867 | 1938 | 2037 | 2135 | 2244 | 2331 | 2490 | 2664 | 2801 | 2888 | 2937 | 3118 | 3369 | |||
41" | 1454 | 1566 | 1635 | 1710 | 1763 | 1822 | 1891 | 1987 | 2083 | 2189 | 2275 | 2492 | 2599 | 2733 | 2818 | 2866 | 3042 | 3287 | |||
42" | 1420 | 1529 | 1596 | 1669 | 1721 | 1778 | 1846 | 1940 | 2033 | 2137 | 2220 | 2371 | 2538 | 2668 | 2751 | 2798 | 2969 | 3208 | |||
43" | 1387 | 1493 | 1559 | 1630 | 1681 | 1737 | 1803 | 1894 | 1986 | 2087 | 2169 | 2316 | 2479 | 2606 | 2687 | 2733 | 2900 | 3134 | |||
44" | 1355 | 1459 | 1524 | 1593 | 1643 | 1698 | 1762 | 1851 | 1941 | 2040 | 2119 | 2263 | 2422 | 2545 | 2626 | 2670 | 2834 | 3063 | |||