Gear Ratio & Tire Size Chart
Good "rule of thumb" calculation is to
multiply .12 by your tire diameter. (.12 X 38" = 4.56)
The
below table can be used to get a rough idea on gear ratios. The
colors represent ideal RPMs at highway speeds (65). For highway
cruising and best fuel economy stay towards the yellow (2600
rpm), around town daily driving is color coded green (2800 rpm),
and for better towing power or just more 4-low power use the
ratios near the red (3100 rpm). These calculations are assuming
a manual transmission with a 1:1 ratio. If you drive an
automatic your RPMs will be slightly higher, and the opposite is
true if you have overdrive (your RPMs will be slightly lower).
Better Gas
Mileage |
Near
Factory Ratio |
More Power |
|
Gear Ratio |
T
i
r
e
D
i
a
m
e
t
e
r
|
|
|
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 |
|
Weight of Round Steel Tubing
Outside
Dia. Wall
Thickness Weight
per Foot
1.25
.049
0.629
1.25
.095
1.172
1.25
.120
1.448
1.5
.049
0.759
1.5
.065
0.996
1.5
.083
1.256
1.5
.095
1.426
1.5
.120
1.769
1.75
.049
0.890
1.75
.065
1.170
1.75
.083
1.478
1.75
.095
1.679
1.75
.120
2.089
2.0
.049
1.021
2.0
.065
1.343
2.0
.083
1.699
2.0
.095
1.933
2.0
.120
2.409
|
|
|