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Fixed Gear math
Gear Inches:
Gear Inches Formula:
Speed based on gear and RPM:
Know of more? |
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| -- CHAINRING TEETH -- |
|
| 30
| 32
| 34
| 36
| 38
| 39
| 40
| 42
| 44
| 46
| 48
| 50
| 52
| 53
|
11
| 73.6
| 78.5
| 83.4
| 88.4
| 93.3
| 95.7
| 98.2
| 103.1
| 108.0
| 112.9
| 117.8
| 122.7
| 127.6
| 130.1
|
12
| 67.5
| 72.0
| 76.5
| 81.0
| 85.5
| 87.7
| 90.0
| 94.5
| 99.0
| 103.5
| 108.0
| 112.5
| 117.0
| 119.2
|
13
| 62.3
| 66.5
| 70.6
| 74.8
| 78.9
| 81.0
| 83.1
| 87.2
| 91.4
| 95.5
| 99.7
| 103.8
| 108.0
| 110.1
|
14
| 57.9
| 61.7
| 65.6
| 69.4
| 73.3
| 75.2
| 77.1
| 81.0
| 84.9
| 88.7
| 92.6
| 96.4
| 100.3
| 102.2
|
15
| 54.0
| 57.6
| 61.2
| 64.8
| 68.4
| 70.2
| 72.0
| 75.6
| 79.2
| 82.8
| 86.4
| 90.0
| 93.6
| 95.4
|
16
| 50.6
| 54.0
| 57.4
| 60.7
| 64.1
| 65.8
| 67.5
| 70.9
| 74.2
| 77.6
| 81.0
| 84.4
| 87.7
| 89.4
|
17
| 47.6
| 50.8
| 54.0
| 57.2
| 60.3
| 61.9
| 63.5
| 66.7
| 69.9
| 73.1
| 76.2
| 79.4
| 82.6
| 84.2
|
18
| 45.0
| 48.0
| 51.0
| 54.0
| 57.0
| 58.5
| 60.0
| 63.1
| 66.0
| 69.0
| 72.0
| 75.0
| 78.0
| 79.5
|
19
| 42.6
| 45.5
| 48.3
| 51.2
| 54.0
| 55.4
| 56.8
| 59.7
| 62.5
| 65.4
| 68.2
| 71.0
| 73.9
| 75.3
|
20
| 40.5
| 43.2
| 45.9
| 48.6
| 51.3
| 52.6
| 54.0
| 56.7
| 59.4
| 62.1
| 64.8
| 67.5
| 70.2
| 71.5
|
21
| 38.6
| 41.1
| 43.7
| 46.3
| 48.9
| 50.1
| 51.4
| 54.0
| 56.6
| 59.1
| 61.7
| 64.3
| 66.9
| 68.1
|
22
| 36.8
| 39.3
| 41.7
| 44.2
| 46.6
| 47.9
| 49.1
| 51.5
| 54.0
| 56.4
| 58.9
| 61.4
| 63.8
| 65.0
|
23
| 35.2
| 37.6
| 39.9
| 42.3
| 44.6
| 45.8
| 47.0
| 49.3
| 51.6
| 54.0
| 56.3
| 58.7
| 61.0
| 62.2
|
24
| 33.7
| 36.0
| 38.2
| 40.5
| 42.7
| 43.9
| 45.0
| 47.2
| 49.5
| 51.7
| 54.0
| 56.2
| 58.5
| 59.6
|
25
| 32.4
| 34.6
| 36.7
| 38.9
| 41.0
| 42.1
| 43.2
| 45.4
| 47.5
| 49.7
| 51.8
| 54.0
| 56.2
| 57.2
|
26
| 31.1
| 33.2
| 35.3
| 37.4
| 39.5
| 40.5
| 41.5
| 43.6
| 45.7
| 47.8
| 49.8
| 51.9
| 54.0
| 55.0
|
27
| 30.0
| 32.0
| 34.0
| 36.0
| 38.0
| 39.0
| 40.0
| 42.0
| 44.0
| 46.0
| 48.0
| 50.0
| 52.0
| 53.0
|
28
| 28.9
| 30.9
| 32.8
| 34.7
| 36.6
| 37.6
| 38.6
| 40.5
| 42.4
| 44.4
| 46.3
| 48.2
| 50.1
| 51.1
|
30
| 27.0
| 28.8
| 30.6
| 32.4
| 34.2
| 35.1
| 36.0
| 37.8
| 39.6
| 41.4
| 43.2
| 45.0
| 46.8
| 47.7
|
32
| 25.3
| 27.0
| 28.7
| 30.4
| 32.1
| 32.9
| 33.8
| 35.4
| 37.1
| 38.8
| 40.5
| 42.2
| 43.9
| 47.7
|
Table taken with generous permission from David Wolfe
http://home.i1.net/~dwolfe/gerz/
Gear Inches Formula
(Drive Wheel Diameter x # of chainRing teeth) / rearCog
Speed using pedaling RPM:
Using a 23mm tire:
rpm x gear ratio x (1/12.6) = speed (in mph)
Know of other interesting formulae? email me and I can add it: gEo
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