BMX Gear Ratio Guide

Gear Ratio = (Wheel Diameter x # Teeth on Front Sprocket) / (# Teeth on Rear Sprocket)

20” Sew-Up Tire (Diameter 19”)

19	36	37	38	39	40	41	42	43	44	45	46	47	48
11	62.2	63.9	65.6	67.4	69.1	70.8	72.5	74.3	76.0	77.7	79.5	81.2	82.9
12	57.0	58.6	60.2	61.8	63.3	64.9	66.5	68.1	69.7	71.3	72.8	74.4	76.0
13	52.6	54.1	55.5	57.0	58.5	59.9	61.4	62.8	64.3	65.8	67.2	68.7	70.2
14	48.9	50.2	51.6	52.9	54.3	55.6	57.0	58.4	59.7	61.1	62.4	63.8	65.1
15	45.6	46.9	48.1	49.4	50.7	51.9	53.2	54.5	55.7	57.0	58.3	59.5	60.8
16	42.8	43.9	45.1	46.3	47.5	48.7	49.9	51.1	52.3	53.4	54.6	55.8	57.0
17	40.2	41.4	42.5	43.6	44.7	45.8	46.9	48.1	49.2	50.3	51.4	52.5	53.6
18	38.0	39.1	40.1	41.2	42.2	43.3	44.3	45.4	46.4	47.5	48.6	49.6	50.7
19	36.0	37.0	38.0	39.0	40.0	41.0	42.0	43.0	44.0	45.0	46.0	47.0	48.0
20	34.2	35.2	36.1	37.1	38.0	39.0	39.9	40.9	41.8	42.8	43.7	44.7	45.6
21	32.6	33.5	34.4	35.3	36.2	37.1	38.0	38.9	39.8	40.7	41.6	42.5	43.4

20 x 1.75 Tire (Diameter 19.5”)

19.5	36	37	38	39	40	41	42	43	44	45	46	47	48
11	63.8	65.6	67.4	69.1	70.9	72.7	74.5	76.2	78.0	79.8	81.5	83.3	85.1
12	58.5	60.1	61.8	63.4	65.0	66.6	68.3	69.9	71.5	73.1	74.8	76.4	78.0
13	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
14	50.1	51.5	52.9	54.3	55.7	57.1	58.5	59.9	61.3	62.7	64.1	65.5	66.9
15	46.8	48.1	49.4	50.7	52.0	53.3	54.6	55.9	57.2	58.5	59.8	61.1	62.4
16	43.9	45.1	46.3	47.5	48.8	50.0	51.2	52.4	53.6	54.8	56.1	57.3	58.5
17	41.3	42.4	43.6	44.7	45.9	47.0	48.2	49.3	50.5	51.6	52.8	53.9	55.1
18	39.0	40.1	41.2	42.3	43.3	44.4	45.5	46.6	47.7	48.8	49.8	50.9	52.0
19	36.9	38.0	39.0	40.0	41.1	42.1	43.1	44.1	45.2	46.2	47.2	48.2	49.3
20	35.1	36.1	37.1	38.0	39.0	40.0	41.0	41.9	42.9	43.9	44.9	45.8	46.8
21	33.4	34.4	35.3	36.2	37.1	38.1	39.0	39.9	40.9	41.8	42.7	43.6	44.6

20 x 2.125 Tire (Diameter 20”)

20

36

37

38

39

40

41

42

43

44

45

46

47