History

Gear Inch Chart

 

Gear Inches are used to give a numerical value to how a particular chainwheel/cog combination will feel.

Classic BMX gearing evolved over the years to be 44/16,which has 55 gear inches. The most popular gear ratios are pretty close to a 55 inch, which just seems to feel best for most people. In the charts below, I’ve bolded the most common combo’s. The number is derived from a simple formula: (chainring size divided by cog size) multiplied by wheel size.
 

 
BMX 24" Wheel
9
10
11
12
13
14
15
16
17
18
23
61.3
55.2
50.2
46
42.5
39.4
36.8
34.5
32.5
30.7
24
64
57.6
52.4
48
44.3
41.1
38.4
36
33.9
32
25
66.7
60
54.5
50
46.2
42.9
40
37.5
35.3
33.3
26
69.3
62.4
56.7
52
48
44.6
41.6
39
36.7
34.7
27
72
64.8
58.9
54
49.8
46.3
43.2
40.5
38.1
36
28
74.7
67.2
61.1
56
51.7
48
44.8
42
39.5
37.3
29
77.3
69.6
63.3
58
53.5
49.7
46.4
43.5
40.9
38.7
30
80
72
65.5
60
55.4
51.4
48
45
42.2
40
31
82.7
74.4
67.6
62
57.2
53.1
49.6
46.5
43.8
41.3
32
85.3
76.8
69.8
64
59.1
54.9
51.2
48
45.2
42.7
33
88
79.2
72
66
60.9
56.6
52.8
49.5
46.6
44
34
90.7
81.6
74.2
68
62.8
58.3
54.4
51
48
45.3
35
93.3
84
76.4
70
64.6
60
56
52.5
49.4
46.7
36
96
86.4
78.5
72
66.5
61.7
57.6
54
50.8
48
37
98.7
88.8
80.7
74
68.3
63.4
59.2
55.5
52.2
49.3
38
101.3
91.2
82.9
76
70.2
65.1
60.8
57
53.6
50.7
39
104
93.6
85.1
78
72
66.9
62.4
58.5
55.1
52
40
106.7
96
87.3
80
73.8
68.6
64
60
56.5
53.3
41
109.3
98.4
89.5
82
75.7
70.3
65.6
61.5
57.9
54.7
42
112
100.8
91.6
84
77.5
72
67.2
63
59.3
56
43
114.7
103.2
93.8
86
79.4
73.7
68.8
64.5
60.7
57.3
44
117.3
105.6
96
88
81.2
75.4
70.4
66
62.1
58.7
45
120
108
98.2
90
83.1
77.1
72
67.5
63.5
60
46
122.7
110.4
100.4
92
84.9
78.9
73.6
69
64.9
61.3
47
125.3
112.8
102.5
94
86.8
80.6
75.2
70.2
66.4
62.7
48
128
115.2
104.7
96
88.6
82.3
76.8
72
67.8
64
49
130.7
117.6
106.9
98
90.5
84
78.4
73.5
69.2
65.3
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BMX 20" Wheel
9
10
11
12
13
14
15
16
17
18
23
51.1
46
41.8
38.3
35.4
32.9
30.7
28.8
27.1
25.6
24
53.3
48
43.6
40
36.9
34.3
32
30
28.2
26.7
25
55.6
50
45.5
41.7
38.5
35.7
33.3
31.3
29.4
27.8
26
57.8
52
47.3
43.3
40
37.1
34.7
32.5
30.6
28.9
27
60
54
49.1
45
41.5
38.6
36
33.8
31.8
30
28
62.2
56
50.9
46.7
43.1
40
37.3
35
32.9
31.1
29
64.4
58
52.7
48.3
44.6
41.4
38.7
36.3
34.1
32.2
30
66.7
60
54.5
50
46.2
42.9
40
37.5
35.3
33.3
31
68.9
62
56.4
51.7
47.7
44.3
41.3
38.8
36.5
34.4
32
71.1
64
58.2
53.3
49.2
45.7
42.7
40
37.6
35.6
33
73.3
66
60
55
50.8
47.1
44
41.3
38.8
36.7
34
75.6
68
61.8
56.7
52.3
48.6
45.3
42.5
40
37.8
35
77.8
70
63.6
58.3
53.8
50
46.7
43.8
41.2
38.9
36
80
72
65.5
60
55.4
51.4
48
45
42.4
40
37
82.2
74
67.3
61.7
56.9
52.9
49.3
46.3
43.5
41.1
38
84.4
76
69.1
63.3
58.5
54.3
50.7
47.5
44.7
42.2
39
86.7
78
70.9
65
60
55.7
52
48.8
45.9
43.3
40
88.9
80
72.7
66.7
61.5
57.1
53.3
50
47.1
44.4
41
91.1
82
74.5
68.3
63.1
58.6
54.7
51.3
48.2
45.6
42
93.3
84
76.4
70
64.6
60
56
52.5
49.4
46.7
43
95.6
86
78.2
71.7
66.2
61.4
57.3
53.8
50.6
47.8
44
97.8
88
80
73.3
67.7
62.9
58.7
55
51.8
48.9
45
100
90
81.8
75
69.2
64.3
60
56.3
52.9
50
46
102.2
92
83.6
76.7
70.8
65.7
61.3
57.5
54.1
51.1
47
104.4
94
85.5
78.3
72.3
67.1
62.7
58.8
55.3
52.2
48
106.7
96
87.3
80
73.8
68.6
64
60
56.5
53.3
49
108.9
98
89.1
81.7
75.4
70
65.3
61.3
57.6
54.4
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