Top: Home page
Up: Table of contents Reverse-engineering calculations for this hub
SRAM I-Motion 9[1]
  Number of gear teeth Drive path Ratios  
Shifter Position Sun Gear 1 Pinion meshing with sun  Pinion meshing with ring Ring gear 1=R to P, 2=Direct, 3=P to R Drive ratio as fraction Drive ratio from bro- chure Ratio incre- ment
1 36 13 22 72 1   13/24 0.542 0.542  
2 30 15 22 72 1   18/29 0.621 0.621 1.146
3 27 22 22 72 1    8/11 0.727 0.727 1.172
4 18 32 22 72 1   64/75 0.853 0.853 1.173
5 18 32 22 72 2 1        1.000 1.000 1.172
6 18 32 22 72 3 1  11/64 1.172 1.172 1.172
7 27 22 22 72 3 1   3/8  1.375 1.375 1.173
8 30 15 22 72 3 1  11/18 1.611 1.611 1.172
9 36 13 22 72 3 1  11/13 1.846 1.844[2] 1.146
[1]
John Allen:
Calculated and probably correct, buit note minor discrepancy with SRAM literature. The SRAM value of 1.844 for the top gear does not produce the same increment between the top two gears as between the bottom two gears!
[2]
John Allen:
Note discrepancy. SRAM data appear to be incorrect.