Gear Ratio Chart
Special Thanks to: MWytt7371@aol.com
Overall final drive ratio (including tire size). This is the real gear
ratio- you must consider tire size to accurately pick the right gears. Too
high, your car runs hot; geared too low, no speed.
Formula- for finding overall drive ratio is: spur (axle) gear, divided by
pinion (motor) gear, divided by the tire size in thousandths.
Ex.: 37 / 11 = 3.364; 3.36 / .765 = 4.39:1
To use this chart, find the chart for your pinion, 8, 9,10, or 11. Keep in
mind that the tech tool must clear the gear by the track minimum (usually
1/16), meaning that a large spur (axle) gear will not clear- for example,
an 11:39 with a .765 tire may have the right ratio, but would probably NOT
clear the track.
Select the final drive ratio you want, and put on the tires and spur gear to
reach that ratio.
8 tooth pinion
36 37 38 39
Tire Size;
.785 5.73 5.89 6.05 6.21
.780 5.77 5.93 6.09 6.25
.775 5.81 5.97 6.13 6.29
.770 5.84 6.00 6.17 6.32
.765 5.88 6.04 6.21 6.36
.760 5.92 6.08 6.25 6.40
.755 5.96 6.12 6.29 6.44
9 tooth pinion 48 pitch gears I 64 pitch gears
29 30 31 32 35 36 37 38 39
Tire Size;
.875 (7/8) 3.68 3.81 3.94 4.06 4.44 4.57 4.70 4.83 4.95
.812 (13/16) 3.97 4.11 4.24 4.38 4.79 4.93 5.06 5.20 5.34
.800 4.03 4.17 4.30 4.45 4.86 5.00 5.14 5.28 5.42
.795 4.05 4.20 4.33 4.48 4.89 5.03 5.17 5.31 5.45
.790 4.08 4.23 4.36 4.50 4.92 5.06 5.20 5.34 5.49
.785 4.10 4.25 4.39 4.53 4.95 5.10 5.24 5.38 5.52
.780 4.13 4.27 4.42 4.56 4.99 5.13 5.27 5.41 5.55
.775 4.16 4.30 4.44 4.59 5.02 5.16 5.30 5.45 5.59
.770 4.18 4.32 4.47 4.62 5.05 5.19 5.34 5.48 5.63
.765 4.21 4.36 4.50 4.65 5.08 5.23 5.37 5.52 5.66
.760 4.24 4.39 4.53 4.68 5.12 5.26 5.41 5.56 5.70
10 tooth pinion
31 32 35 36 37 38 39 40 41
Tire Size;
.812 (13/16) 3.82 3.94 4.31 4.43 4.56 4.68 4.80 4.92 5.05
.800 3.88 4.00 4.38 4.50 4.63 4.75 4.88 5.00 5.13
.795 3.90 4.03 4.40 4.53 4.65 4.78 4.91 5.03 5.16
.790 3.92 4.05 4.43 4.52 4.68 4.81 4.94 5.06 5.19
.785 3.95 4.08 4.46 4.59 4.71 4.84 4.97 5.10 5.22
.780 3.97 4.10 4.49 4.62 4.74 4.87 5.00 5.13 5.26
.775 4.00 4.13 4.52 4.65 4.77 4.90 5.03 5.16 5.29
.770 4.03 4.16 4.55 4.68 4.81 4.94 5.06 5.19 5.32
.765 4.05 4.18 4.58 4.71 4.84 4.97 5.10 5.23 5.36
.760 4.08 4.21 4.60 4.74 4.87 5.00 5.13 5.26 5.39
.755 4.11 4.24 4.64 4.77 4.90 5.03 5.17 5.30 5.43
11 tooth pinion
36 37 38 39 40 41 42
Tire Size;
.812 (13/16) 4.03 4.14 4.25 4.37 4.48 4.59 4.70
.800 4.09 4.20 4.32 4.43 4.55 4.66 4.77
.795 4.12 4.23 4.35 4.46 4.57 4.69 4.80
.790 4.14 4.26 4.37 4.49 4.60 4.72 4.83
.785 4.17 4.28 4.40 4.52 4.63 4.75 4.86
.780 4.20 4.31 4.43 4.55 4.66 4.78 4.90
.775 4.22 4.34 4.46 4.57 4.69 4.81 4.93
.770 4.25 4.37 4.49 4.60 4.72 4.84 4.96
.765 4.28 4.39 4.52 4.63 4.75 4.87 4.99
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