Gear Ratios; For mountain climbing ideal is 2.15. Those figures, or ones that come close are highlighted in green.





For 8 Tooth Drivers
(given in 9 tooth equivalent numbers)
(Example: 20/40 with 9 tooth drivers is the same final drive ratio as 22/39 with 8s)

8 Tooth Driver 17T 18T 19T 20T 21T 22T 23T
39T N/A 2.44 / 68L 2.31 / 68L 2.19 / 68L 2.09 / 68L 2.00 / 70L 1.91 / 70L
40T 2.65 / 68L 2.50 / 68L 2.37 / 68L 2.25 / 68L 2.14 / 70L 2.05 / 70L 1.96 / 70L
42T 2.78 / 68L 2.63 / 68L 2.49 / 68L 2.36 / 68L 2.25 / 70L 2.15 / 70L 2.05 / 72L

 

For 9 Tooth Drivers. Editor's note: The larger (bottom gear) figures were carried out, with the same formula, however chain lengh is unknown, at this time.

9 Tooth Driver. 17T 18T 19T 20T 21T 22T 23T
39T N/A 2.17 / 68L 2.05 / 68L 1.95 / 68L 1.86 / 68L 1.77 / 70L 1.70 / 70L
40T 2.35 / 68L 2.22 / 68L 2.11 / 68L 2.00 / 68L 1.90 / 70L 1.82 / 70L 1.74 / 70L
42T 2.47 / 68L 2.33 / 68L 2.21 / 68L 2.10 / 68L 2.00 / 70L 1.91 / 70L 1.83 / 72L
43T 2.53 / ??L 2.39 / ??L 2.26 / ??L 2.15 / ??L 2.05 / ??L 1.95 / ??L 1.87 / ??L
44T 2.59 / ??L 2.44 / ??L 2.31 / ??L 2.20 / ??L 2.09 / ??L 2.00 / ??L 1.91 / ??L
45T 2.65 / ??L 2.50 / ??L 2.37 / ??L 2.25 / ??L 2.14 / ??L 2.04 / ??L 1.96 / ??L
46T 2.70 / ??L 2.55 / ??L 2.42 / ??L 2.30 / ??L 2.19 / ??L 2.09 / ??L 2.00 / ??L


For 10 Tooth Drivers
(given in 9 tooth equivalent numbers)
(Example: 20/40 with 9 tooth drivers is the same final drive ratio as 18/40 with 10s) Editor's note: I carried the figures onto 46 bottom gear with 10 drivers, using the formula of bottom gear divided by top, and multiplied by the 10 driver factor of .9012875. This is for general information; For a serious conversion, you need to verify the accuracy. Also chain lengh in these figures are unknown, at this time.

10 Tooth Driver 17T 18T 19T 20T 21T 22T 23T
39T N/A 1.95 / 68L 1.85 / 68L 1.76 / 68L 1.67 / 68L 1.60 / 70L 1.53 / 70L
40T 2.12 / 68L 2.00 / 68L 1.89 / 68L 1.80 / 68L 1.71 / 70L 1.64 / 70L 1.57 / 70L
42T 2.22 / 68L 2.10 / 68L 1.99 / 68L 1.89 / 68L 1.80 / 70L 1.72 / 70L 1.64 / 72L
43T 2.81 / ??L 2.15 / ??L 2.04 / ??L 1.94 / ??L 1.84 / ??L 1.76 / ??L 1.68 / ??L
44T 2.33 / ??L 2.20 / ??L 2.09 / ??L 1.98 / ??L 1.88 / ??L 1.80 / ??L 1.72 / ??L
45T 2.38 / ??L 2.25 / ??L 2.13 / ??L 2.03 / ??L 1.93 / ??L 1.84 / ??L 1.76 / ??L
46T 2.44 / ??L 2.30 / ??L 2.18 / ??L 2.07 / ??L 1.97 / ??L 1.88 / ??L 1.80 / ??L


[karl's home direction]