Gear Ratio Chart/Pinion Gear Selection - Evader ST/BX With 85T Spur
Internal Gear Ratio 2.66
  Off-Road Tires Street Tires Foam Tires * Off-road calcs = Gladiator II tires w/ 4.25" diameter
Roll-out 13.352 10.996 9.425 * Street calcs = Street Hawg II tires w/ 3.5" diameter
* Foam calcs = Generic foam tires w/ 3.0" diameter
Final Drive Ratios
Pinion FDR (*:1) Pinion FDR (*:1)
15 15.073 21 10.767
16 14.131 22 10.277
17 13.300 23 9.830
18 12.857 24 9.421
19 11.900 25 9.044
20 11.305 26 8.696
Efficiency Ratio1
Pinion FDR:RO - Off-Road Pinion FDR:RO - Street Pinion FDR:RO - Foam
15 1.129 15 1.371 15 1.599
16 1.058 16 1.285 16 1.499
17 0.996 17 1.210 17 1.411
18 0.963 18 1.169 18 1.364
19 0.891 19 1.082 19 1.263
20 0.847 20 1.028 20 1.199
21 0.806 21 0.979 21 1.142
22 0.770 22 0.935 22 1.090
23 0.736 23 0.894 23 1.043
24 0.706 24 0.857 24 1.000
25 0.677 25 0.823 25 0.960
26 0.651 26 0.791 26 0.923
1 Ideal Efficiency Ratio is closest to 1:1.  Depending on the kV of your motor, you may need to gear up or down to find the sweet spot.
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