The gear chart is a table of computed gear ratios based on three facts. They are the size of the front spocket (Number of teeth on the front chain ring), next the size of the rear spocket cog (Number of teeth on the
rear cog), and last the outside diameter of the tire.

The gear ratio is the number of teeth on the front chain ring divided by the number of teeth on the rear spocket cog.

Example: A 40 tooth front /divided by a 16 tooth rear cog (40T/16T=2.5) shows a ratio of 2.5. The gear ratio is [the number of turns the rear wheel makes per one turn of the front crank chain ring or pedal. Now take this ratio x(times) the out side diameter of the tire. Now working with a 20 x 2.125, or 20 X 1 3/8 tire which has a diameter of 20". The gear number can be computed. Ratio 2.5 X(times) 20" equals 50".

This can be found in the Gear Table under 20x2.125 or 20x1-1/8 tires.

The Gear chart provides a simple method in which a comparison can be accomplished between different gears and wheel sizes.

Once the gear number is available then the distance traveled can be calulated by taking the gear number x(times) 3.1416 (pie).

Example: 50 inch gear number x 3.1416 equals 157 inches/(divided by) 12 inches per foot equals 13.09 feet. Remember this is the distancetraveled per {one turn of the crank}.

The speed of travel [ mph] can be calulated by taking the inch gear number X 3.1416 (pie) x number of the crank turns the cyclist makes per
minute [# rpm] X 60 minutes in an hour/divided by 63,360 inches in a mile.

 

Example 50" gear number X 3.1416 X 90 rpms X 60 min./ divided by 63,360 inches in a mile equals 13.38 mph bike speed.

The important question is will a larger gear produce a faster speed?

Bigger gears do not necessary produce a faster ground speed for the cyclist.

WHY?

The problem is that with each larger gear that is selected a high pedalingforce is required to rotate that next step up in gear size. The crank will have to be turned at the same speed to produced a faster ground speed. It should be noted that a cyclist engery is at a fixed level of out put to the pedal. Thus higher gears do not necessary produce a faster ground speed.

Sew Ups   34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 14 46.1 47.5 48.9 50.3 51.6 53.0 54.3 55.7 57.0 58.4 59.8 61.1 62.5 63.9 65.2 15 43.0 44.3 45.6 46.9 48.2 49.4 50.7 52.0 53.2 54.5 55.8 57.0 58.3 59.6 60.9 16 40.3 41.6 42.8 43.9 45.2 46.3 47.5 48.8 50.0 51.1 52.3 53.5 54.7 55.8 57.0 17 38.0 39.1 40.5 41.4 42.5 43.6 44.7 45.9 47.0 48.1 49.2 50.3 51.4 52.5 53.7 18 35.9 36.8 38.0 39.1 40.1 41.2 42.2 43.3 44.4 45.4 46.5 47.5 48.6 49.6 50.7

20 x 1 1/8   34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 14 48.6 50.0 51.4 52.8 54.3 55.7 57.7 58.6 60.0 61.4 62.8 64.3 65.7 67.1 68.6 15 45.3 46.7 48.0 49.3 50.7 52.0 53.3 54.7 56.0 57.3 58.7 60.0 61.3 62.7 64.0 16 42.5 43.8 45.5 46.2 47.5 48.7 50.0 51.2 52.5 53.7 55.0 56.2 57.5 58.7 60.0 17 40.0 41.2 42.3 43.5 44.7 45.9 47.0 48.2 49.4 50.6 51.8 52.9 54.1 55.3 56.5 18 37.7 38.8 40.0 41.1 42.2 43.3 44.4 45.6 46.7 47.8 48.9 50.0 51.1 52.2 53.3

20 x 1 3/8   34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 14 51.0 52.5 54.0 55.5 57.0 58.5 60.0 61.5 63.0 64.5 66.0 67.5 69.0 70.5 72.0 15 47.6 49.0 50.0 51.8 53.2 54.6 56.0 57.4 58.8 60.2 61.6 63.0 64.4 65.8 67.2 16 44.6 45.9 47.3 48.6 49.9 51.2 52.5 53.9 55.2 56.5 57.8 59.1 60.4 61.7 63.0 17 42.0 43.2 44.5 45.7 47.0 48.2 49.4 50.7 51.9 53.2 54.4 55.6 56.9 58.1 59.3 18 39.7 40.7 42.0 43.2 44.4 45.5 46.7 47.9 49.0 50.2 51.4 52.5 53.7 54.9 56.0

24 x 1.75
	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
14	58.3	60.0	61.7	63.3	65.0	66.9	68.6	70.3	72.0	73.7	75.3	77.0	78.9	80.6	82.3
15	54.4	56.0	57.6	59.3	60.7	62.4	64.1	65.5	67.2	68.9	70.3	72.0	73.7	75.1	76.8
16	51.0	52.5	54.0	55.5	57.0	58.5	60.0	61.4	63.1	64.5	66.0	67.4	69.1	70.5	72.0
17	48.0	49.4	50.8	52.2	53.6	55.1	56.5	57.9	59.3	60.7	62.1	63.6	65.0	66.2	67.7
18	45.3	46.5	48.0	49.4	50.7	52.0	53.3	54.7	56.0	57.3	58.5	60.0	61.4	62.6	64.1

24 x 1 1/8
	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
14	54.9	56.5	58.1	59.7	61.3	63.1	64.7	66.3	67.9	69.4	71.0	72.6	74.4	76.0	77.5
15	51.3	52.8	54.3	55.8	57.3	58.8	60.3	61.8	63.3	64.9	66.3	67.9	69.4	70.8	72.4
16	48.1	49.5	50.9	52.3	53.7	55.1	56.6	57.9	59.5	60.8	62.2	63.9	65.1	66.5	67.9
17	45.2	46.6	47.9	49.3	50.6	51.9	53.2	54.6	55.9	57.2	58.6	59.9	61.3	62.4	63.8
18	42.7	43.9	45.2	46.6	47.7	49.1	50.3	51.5	52.8	54.0	55.3	56.6	57.9	59.0	60.4

24 x 1 3/8
	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
14	58.3	60.0	61.7	63.3	65.0	66.9	68.6	70.3	72.0	73.7	75.3	77.0	78.9	80.6	82.3
15	54.5	56.0	57.6	59.3	60.7	62.4	64.1	65.5	67.2	68.9	70.3	72.0	73.7	75.1	76.8
16	51.0	52.5	54.0	55.5	57.0	58.5	60.0	61.4	63.1	64.5	66.6	67.4	69.1	70.5	72.0
17	48.0	49.4	50.8	52.2	63.6	55.1	56.5	57.9	59.3	60.7	62.1	63.6	65.0	66.2	67.7
18	45.3	46.5	48.0	49.4	50.7	52.0	53.3	54.7	56.0	57.3	58.5	60.0	61.4	62.6	64.1

24 x 1.5
	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
14	55.9	57.5	59.1	60.7	62.3	64.2	65.8	67.4	69.0	70.6	72.2	73.8	75.7	77.3	78.9
15	52.1	53.7	55.2	56.7	58.2	59.8	61.3	62.8	64.4	65.9	67.4	69.0	70.6	72.0	73.6
16	48.8	50.3	51.8	53.2	54.6	56.0	57.5	58.9	60.3	61.8	63.2	64.6	66.2	67.6	69.0
17	46.0	47.3	48.7	50.0	51.4	52.8	54.1	55.5	56.8	58.8	59.5	60.8	62.3	63.5	64.8
18	43.4	44.7	46.0	47.2	48.5	49.8	51.1	52.4	53.7	54.9	56.2	57.5	58.9	60.0	61.4