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Gear Ratio Chart

GEAR RATIO AND TIRE SIZE CALCULATOR

When you change your tire size you need to make sure you have the right gearing to get optimal fuel economy and power. A good way to calculate this is to multiply .12 by your Jeeps tire diameter (Example: .12 X 38" = 4.56). Here at Alloy USA we have a made an easy to read chart to help you decide what is on the best gearing for your Jeep. The three distinct colors below can help you decide what is the right gearing for you... 

When you change your tire size you need to make sure you have the right gearing to get optimal fuel economy and power. A good way to calculate this is to multiply .12 by your Jeeps tire diameter (Example: .12 X 38" = 4.56). Here at Alloy USA we have a made an easy to read chart to help you decide what is on the best gearing for your Jeep. The three distinct colors below can help you decide what is the right gearing for you... 

  • Green = Best MPG, this is what you would want to get for the best fuel economy and highway cruising.
  • Orange = Best Overall, this is good mix of power/MPG and considered best for daily driving.
  • Red = Best Power, this will give you the best performance for towing power, but at the expense of your MPG.


These calculations are assuming a manual transmission at 65 MPH with a gear ratio of 1:1. If you drive an automatic your RPMs will be slightly higher, and if you have overdrive your RPMs will be slightly lower.

 
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
3438
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
 

Here's a formula you can use to calculate your vehicle's tire diameter:

(CROSS SECTION WIDTH x 0.ASPECT RATIO x 2 ÷ 25.4) + WHEEL DIAMETER = OVERALL TIRE DIAMETER

For Example: 235/45ZR-1 (235 x 0.45 x 2 ÷ 25.4) + 17 = 25.327"

And here's a formula that you can use to calculate your vehicle's rear axle gear ratio:

RING GEAR TOOTH COUNT ÷ PINION GEAR TOOTH COUNT = GEAR RATIO

For example: 41-tooth ring gear ÷ 10-tooth pinion gear = 4.10






Posion Spyder Authorized Dealer