Posted On: 2013-08-12
One of the most important aspects of building any vehicle is choosing the proper gear ratio for the wheels and tires. Often overlooked, a set of gears with the right ratio can transform a vehicle from a commuter to a powerhouse. But how do you make the right choice? Well, that’s based on your needs.
For me, I need a combination of fuel efficiency and power since my Jeep Wrangler build is a daily driver. That’s why I run a 4.56 gear ratio with 35″ tires. This gives me decent fuel efficiency at highway speeds, and enough low end power to throttle through difficult obstacles.
Below I’ve outlined a gear ratio chart that cross compares tire size to gear ratio for the ideal RPM. Although an approximation, it is designed to give you an idea of what your RPMs will be at highway speed (65 mph). The three colored bands are for: fuel economy (green), every day driving (yellow) and increased power (red). For simplicity’s sake the chart assumes you have a 1:1 ratio with a manual transmission. Note that automatic transmission RPMs are often slightly higher, while overdrive transmissions tend to be a little lower.
Gear Ratio | ||||||||||||||||
Tire Size | 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 | 7.17 | |
27″ | 2677 | 2766 | 2872 | 3017 | 3163 | 3325 | 3454 | 3689 | 3947 | 4150 | 4279 | 4352 | 4619 | 4991 | 5800 | |
28″ | 2582 | 2668 | 2769 | 2909 | 3050 | 3206 | 3331 | 3557 | 3806 | 4001 | 4126 | 4196 | 4454 | 4813 | 5593 | |
29″ | 2493 | 2576 | 2674 | 2809 | 2945 | 3095 | 3216 | 3434 | 3675 | 3863 | 3984 | 4052 | 4300 | 4647 | 5400 | |
30″ | 2410 | 2490 | 2584 | 2715 | 2846 | 2992 | 3109 | 3320 | 3553 | 3735 | 3851 | 3917 | 4157 | 4492 | 5220 | |
31″ | 2332 | 2409 | 2501 | 2628 | 2755 | 2896 | 3008 | 3213 | 3838 | 3614 | 3727 | 3790 | 4023 | 4347 | 5051 | |
32″ | 2259 | 2334 | 2423 | 2546 | 2696 | 2805 | 2914 | 3112 | 3331 | 3501 | 3610 | 3672 | 3897 | 4211 | 4894 | |
33″ | 2191 | 2263 | 2349 | 2469 | 2588 | 2720 | 2826 | 3018 | 3230 | 3395 | 3501 | 3561 | 3779 | 4093 | 4745 | |
34″ | 2126 | 2197 | 2280 | 2396 | 2512 | 2640 | 2743 | 2929 | 3135 | 3295 | 3398 | 3456 | 3668 | 3963 | 4606 | |
35″ | 2065 | 2134 | 2215 | 2328 | 2440 | 2565 | 2664 | 2845 | 3045 | 3201 | 3301 | 3357 | 3563 | 3850 | 4474 | |
36″ | 2008 | 2075 | 2154 | 2263 | 2372 | 2493 | 2590 | 2766 | 2961 | 3112 | 3209 | 3264 | 3464 | 3743 | 4350 | |
37″ | 1954 | 2019 | 2095 | 2203 | 2308 | 2426 | 2520 | 2692 | 2881 | 3028 | 3123 | 3176 | 3370 | 3642 | 4243 | |
38″ | 1902 | 1966 | 2040 | 2144 | 2247 | 2362 | 2454 | 2621 | 2805 | 2948 | 3040 | 3092 | 3282 | 3546 | 4121 | |
39″ | 1854 | 1915 | 1988 | 2089 | 2190 | 2302 | 2391 | 2554 | 2733 | 2873 | 2962 | 3013 | 3198 | 3455 | 4015 | |
40″ | 1807 | 1867 | 1938 | 2037 | 2135 | 2244 | 2331 | 2490 | 2664 | 2801 | 2888 | 2937 | 3118 | 3369 | 3915 | |
41″ | 1763 | 1822 | 1891 | 1987 | 2083 | 2189 | 2275 | 2429 | 2599 | 2733 | 2818 | 2866 | 3042 | 3287 | 3819 | |
42″ | 1721 | 1778 | 1846 | 1940 | 2033 | 2137 | 2220 | 2371 | 2538 | 2668 | 2751 | 2798 | 2969 | 3208 | 3728 | |
43″ | 1681 | 1737 | 1803 | 1894 | 1986 | 2087 | 2169 | 2316 | 2479 | 2606 | 2687 | 2733 | 2900 | 3134 | 3642 | |
44″ | 1643 | 1698 | 1762 | 1851 | 1941 | 2040 | 2119 | 2263 | 2422 | 2546 | 2626 | 2670 | 2834 | 3063 | 3559 |
Fuel Economy | Everyday Driving | Increased Power |