RPM vs. Gear Ratio
Engine RPM @ 55 MPH by Tire Diameter (in.)
When selecting a gear ratio, you should consider tire size,
transmission ratio,
final gear ratio and engine RPM at cruise speed.
Gear
Ratio
Tire Size
(:1)
|
27"
|
28"
|
29"
|
30"
|
31"
|
32"
|
33"
|
34"
|
35"
|
36"
|
37"
|
38"
|
40"
|
42"
|
44"
|
2.56
|
1,752
|
1,690
|
1,631
|
1,577
|
1,526
|
1,478
|
1,434
|
1,391
|
1,352
|
1,314
|
1,279
|
1,245
|
1,183
|
1,126
|
1,075
|
2.73
|
1,869
|
1,802
|
1,740
|
1,682
|
1,627
|
1,577
|
1,529
|
1,484
|
1,441
|
1,401
|
1,364
|
1,328
|
1,261
|
1,201
|
1,147
|
2.94
|
2,012
|
1,942
|
1,874
|
1,811
|
1,753
|
1,698
|
1,646
|
1,599
|
1,552
|
1,509
|
1,468
|
1,429
|
1,358
|
1,294
|
1,235
|
3.08
|
2,108
|
2,033
|
1,963
|
1,897
|
1,836
|
1,779
|
1,725
|
1,674
|
1,626
|
1,581
|
1,538
|
1,498
|
1,423
|
1,355
|
1,294
|
3.21
|
2,197
|
2,119
|
2,046
|
1,977
|
1,914
|
1,854
|
1,798
|
1,745
|
1,695
|
1,648
|
1,603
|
1,561
|
1,483
|
1,412
|
1,348
|
3.31
|
2,266
|
2,185
|
2,110
|
2,039
|
1,973
|
1,912
|
1,854
|
1,799
|
1,748
|
1,699
|
1,653
|
1,610
|
1,529
|
1,456
|
1,390
|
3.42
|
2,341
|
2,257
|
2,179
|
2,107
|
2,039
|
1,975
|
1,915
|
1,859
|
1,806
|
1,756
|
1,708
|
1,663
|
1,580
|
1,505
|
1,436
|
3.54
|
2,423
|
2,336
|
2,256
|
2,181
|
2,110
|
2,044
|
1,982
|
1,924
|
1,869
|
1,817
|
1,768
|
1,772
|
1,635
|
1,558
|
1,487
|
3.73
|
2,553
|
2,462
|
2,377
|
2,298
|
2,224
|
2,154
|
2,089
|
2,027
|
1,969
|
1,915
|
1,863
|
1,814
|
1,723
|
1,641
|
1,567
|
3.90
|
2,669
|
2,574
|
2,485
|
2,402
|
2,325
|
2,252
|
2,184
|
2,120
|
2,059
|
2,002
|
1,948
|
1,897
|
1,802
|
1,716
|
1,638
|
4.10
|
2,806
|
2,706
|
2,613
|
2,526
|
2,444
|
2,368
|
2,296
|
2,228
|
2,165
|
2,105
|
2,048
|
1,994
|
1,894
|
1,804
|
1,722
|
4.27
|
2,923
|
2,818
|
2,721
|
2,630
|
2,545
|
2,466
|
2,391
|
2,321
|
2,255
|
2,195
|
2,133
|
2,077
|
1,973
|
1,879
|
1,793
|
4.56
|
3,121
|
3,010
|
2,906
|
2,809
|
2,718
|
2,633
|
2,554
|
2,478
|
2,408
|
2,341
|
2,278
|
2,218
|
2,107
|
2,006
|
1,915
|
4.88
|
3,340
|
3,221
|
3,110
|
3,006
|
2,909
|
2,818
|
2,733
|
2,652
|
2,577
|
2,505
|
2,437
|
2,373
|
2,255
|
2,147
|
2,050
|
5.29
|
3,621
|
3,491
|
3,371
|
3,259
|
3,154
|
3,055
|
2,962
|
2,875
|
2,793
|
2,716
|
2,642
|
2,573
|
2,444
|
2,328
|
2,222
|
5.38
|
3,682
|
3,551
|
3,428
|
3,314
|
3,207
|
3,107
|
3,013
|
2,924
|
2,841
|
2,762
|
2,687
|
2,616
|
2,486
|
2,367
|
2,260
|
5.71
|
3,908
|
3,769
|
3,639
|
3,517
|
3,404
|
3,298
|
3,198
|
3,104
|
3,015
|
2,931
|
2,852
|
2,777
|
2,638
|
2,512
|
2,398
|
6.17
|
4,223
|
4,072
|
3,932
|
3,801
|
3,678
|
3,653
|
3,455
|
3,354
|
3,258
|
3,167
|
3,082
|
3,001
|
2,851
|
2,715
|
2,593
|
7.17
|
4,907
|
4,732
|
4,569
|
4,417
|
4,274
|
4,141
|
4,015
|
3,897
|
3,786
|
3,681
|
3,581
|
3,487
|
3,313
|
3,155
|
3,011
|
Generally,
the acceptable
RPM range is 2000 to 3000, which is
represented by the entire shaded area of the chart. The optimum RPM
range is 2300 to 2600, and it is represented by the green shading.
