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Sturmey-Archer XRF8[1]
  Number of gear teeth       Number of gear teeth           Number of gear teeth            
Gear Sun Gear 1 Pinion to Sun 1 Pinion to Ring 1 Ring gear 1 1=R to P, 2=Direct Stage 1 Gear Drive Ratio Stage 1 drive ratio as fraction Sun Gear  2 Pinion to Sun 2 Pinion to Ring 2 Ring gear 2 Path: 2=Direct, 3=P to R Stage 2 Gear Drive Ratio Stage 2 drive ratio as fraction Stages 1 and 2 Drive Ratio[2] Stages 1 and 2 drive ratio as fraction Sun Gear  3 Pinion to Sun 3 Pinion to Ring 3 Ring gear 3 Path: 1=P to S, 2=Direct  Stage 3 Gear Drive Ratio Stage 3 drive ratio as fraction Total Drive Ratio[3] Total drive ratio as fraction Ratio incre- ment
1 63 14 14 93 2 1.000 1           39 30 21 90 2 1.000 1           1.000 1           39 21 21 81 2 1.000 1           1.000 1            
2 63 14 14 93 2 1.000 1           39 30 21 90 3 1.303 1   91/300  1.303 1   91/300  39 21 21 81 2 1.000 1           1.303 1   91/300  1.303
3 63 14 14 93 2 1.000 1           39 30 21 90 2 1.000 1           1.000 1           39 21 21 81 3 1.481 1   13/27   1.481 1   13/27   1.137
4 63 14 14 93 3 1.677 1   21/31   39 30 21 90 2 1.000 1           1.677 1   21/31   39 21 21 81 2 1.000 1           1.677 1   21/31   1.132
5 63 14 14 93 2 1.000 1           39 30 21 90 3 1.303 1   91/300  1.303 1   91/300  39 21 21 81 3 1.481 1   13/27   1.931[4] 1  377/405  1.151
6 63 14 14 93 3 1.677 1   21/31   39 30 21 90 3 1.303 1   91/300  2.186 2  433/2325 39 21 21 81 2 1.000 1           2.186[5] 2  433/2325 1.132
7 63 14 14 93 3 1.677 1   21/31   39 30 21 90 2 1.000 1           1.677 1   21/31   39 21 21 81 3 1.481 1   13/27   2.485[6] 2  406/837  1.137 2080[7] 837[8] 0.000000000000000
8 63 14 14 93 3 1.677 1   21/31   39 30 21 90 3 1.303 1   91/300  2.186 2  433/2325 39 21 21 81 3 1.481 1   13/27   3.239[9] 3 2999/12555 1.303 40664[10] 12555[11] 0.000000000000000
[1]
John Allen:
Drive ratios are from gear-tooth counts by David Moorehouse.
[2]
John Allen:
This is the gear ratio after the second stage, the product of its ratio and that of the first stage.
[3]
John Allen:
This is the final drive ratio, the product of the ratios of all three stages.
 Sturmey-archer onliy give this ratio to 2 desimal places, and sometiems inaccurately as indicated in additional comments.
[4]
John Allen:
Sturmey-Archer literature says 1.92
[5]
John Allen:
Sturmey-Archer literature says 2.20
[6]
John Allen:
 Sturmey-Archer literature says 2.50
[7]
John Allen:
Numerator calculated from proper fracdtion
[8]
John Allen:
Denominator entered as an integer.
[9]
John Allen: Sturmey-Archer literature says 3.25
[10]
John Allen:
Numerator entered as an integer
[11]
John Allen:
Denominator entered as an integer.