ABCDEFGHIJKLMNOPQRSTUVWXYZAAAB
1
2
Wheel Circumference (mm)
2108
<--- Modify this number to suit your setup
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4
Gear InchesThe “correct” way to calculate wheel circumference
5
ChainringDifferent tyres and different tyre widths give different wheel diameters. Accurately obtaining your wheel circumference is a fairly easy exercise with the help of a friend and smooth, flat piece of pavement:

2. Pump the tyres up to race pressure.
3. Make a mark on the pavement and a mark on the side of your rear tyre.
4. Line up the two marks so the tyre mark is as close the ground as possible.
5. Sit on your bike and role the bike forward to the rear wheel travels exactly one full revolution. Make a second mark on the ground at the point where the tyre mark is again closest to the ground.
6. Measure the distance between the two marks.

You now have your actual wheel circumference which can now be used for calculating accurate gear roll outs and gear inches. This is particularly useful for riders with gear restrictions or who are looking at target cadence ranges.
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44454647484950515253545556
7
Cog1296.8699.06101.27103.47105.67107.87110.07112.27114.47116.68118.88121.08123.28
8
1389.4191.4493.4895.5197.5499.57101.60103.64105.67107.70109.73111.77113.80
9
1483.0384.9186.8088.6990.5792.4694.3596.2398.12100.01101.89103.78105.67
10
1577.4979.2581.0182.7784.5486.3088.0689.8291.5893.3495.1096.8698.62
11
1672.6574.3075.9577.6079.2580.9082.5584.2085.8687.5189.1690.8192.46
12
1768.3769.9371.4873.0474.5976.1477.7079.2580.8182.3683.9185.4787.02
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1864.5866.0467.5168.9870.4571.9173.3874.8576.3277.7879.2580.7282.19
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15
Gear Meters
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Chainring
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44454647484950515253545556
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Cog127.737.918.088.268.438.618.788.969.139.319.499.669.84
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137.137.307.467.627.787.958.118.278.438.598.768.929.08
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146.636.786.937.087.237.387.537.687.837.988.138.288.43
21
156.186.326.466.616.756.897.037.177.317.457.597.737.87
22
165.805.936.066.196.326.466.596.726.856.987.117.257.38
23
175.465.585.705.835.956.086.206.326.456.576.706.826.94
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185.155.275.395.505.625.745.865.976.096.216.326.446.56
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26
Gear inches90.57
<--- Modify this number to suit your setup
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28
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30
35.080.7
31
35.581.9
32
36.083.0
33
36.584.2
34
37.085.3
35
37.586.5
36
38.087.6
37
38.588.8
38
39.089.9
39
39.591.1
40
40.092.2
41
40.593.4
42
41.094.5
43
41.595.7
44
42.096.8
45
42.598.0
46
43.099.1
47
43.5100.3
48
44.0101.5
49
44.5102.6
50
45.0103.8
51
45.5104.9
52
46.0106.1
53
46.5107.2
54
47.0108.4
55
47.5109.5
56
48.0110.7
57
48.5111.8
58
49.0113.0
59
49.5114.1
60
50.0115.3
61
50.5116.4
62
51.0117.6
63
51.5118.7
64
52.0119.9
65
52.5121.1
66
53.0122.2
67
53.5123.4
68
54.0124.5
69
54.5125.7
70
55.0126.8
71
55.5128.0
72
56.0129.1
73
56.5130.3
74
57.0131.4
75
57.5132.6
76
58.0133.7
77
58.5134.9
78
59.0136.0
79
59.5137.2
80
60.0138.3
81
60.5139.5
82
61.0140.6
83
61.5141.8
84
62.0143.0
85
62.5144.1
86
63.0145.3
87
63.5146.4
88
64.0147.6
89
64.5148.7
90
65.0149.9
91
92
93
94
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96
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99
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