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Getting back up to speed

Gear changes, transmission swaps and tire sizes. All these changes can cause problems with accurate speedometer readings. These charts should help you narrow down the selection of the proper gear combination to use in the transmission and speedo cable to 'get you legal' again.

Here is how this works.

We also have a chart available which provides your gear ratio by comparing rpm's vs tire size.

Credits:

Large Speedo Gears
Multiply rear axle by 20.2 and divide by tire diameter.    
Look up the result on this chart and use the closest number.    
  ( # of teeth on gear )
Calculated Ratio Transmission Gear Speedo Gear
2.06 18 37
2.11 18 38
2.12 17 36
2.17 18 39
2.18 17 37
2.19 16 35
2.22 18 40
2.24 17 38
2.25 16 36
2.28 18 41
2.29 17 39
2.31 16 37
2.33 15 35
2.33 18 42
2.35 17 40
2.38 16 38
2.39 18 43
2.4 15 36
2.41 17 41
2.44 16 39
2.44 18 44
2.47 15 37
2.47 17 42
2.5 14 35
2.5 16 40
2.5 18 45
2.53 15 38
2.53 17 43
2.56 16 41
2.57 14 36
2.59 17 44
2.6 15 39
2.62 16 42
2.64 14 37
2.65 17 45
2.67 15 40
2.69 13 35
2.69 16 43
2.71 14 38
2.73 15 41
2.75 16 44
2.77 13 36
2.79 14 39
2.8 15 42
2.81 16 45
2.85 13 37
2.86 14 40
2.87 15 43
2.92 12 35
2.92 13 38
2.93 14 41
2.93 15 44
3 12 36
3 13 39
3 14 42
3 15 45
3.07 14 43
3.08 12 37
3.08 13 40
3.14 14 44
3.15 13 41
3.17 12 38
3.18 11 35
3.21 14 45
3.23 13 42
3.25 12 39
3.27 11 36
3.31 13 43
3.33 12 40
3.36 11 37
3.38 13 44
3.42 12 41
3.45 11 38
3.46 13 45
3.5 10 35
3.5 12 42
3.55 11 39
3.58 12 43
3.6 10 36
3.64 11 40
3.67 12 44
3.7 10 37
3.73 11 41
3.75 12 45
3.8 10 38
3.82 11 42
3.89 9 35
3.9 10 39
3.91 11 43
4 9 36
4 10 40
4 11 44
4.09 11 45
4.1 10 41
4.11 9 37
4.2 10 42
4.22 9 38
4.3 10 43
4.33 9 39
4.38 8 35
4.4 10 44
4.44 9 40
4.5 8 36
4.5 10 45
4.56 9 41
4.62 8 37
4.67 9 42
4.75 8 38
4.78 9 43
4.88 8 39
4.89 9 44
5 7 35
5 8 40
5 9 45
5.12 8 41
5.14 7 36
5.25 8 42
5.29 7 37
5.38 8 43
5.43 7 38
5.5 8 44
5.57 7 39
5.62 8 45
5.71 7 40
5.86 7 41
6 7 42
6.14 7 43
6.29 7 44
6.43 7 45

Small Speedo Gears
Multiply rear axle by 20.2 and divide by tire diameter.    
Look up the result on this chart and use the closest number.    
  ( # of teeth on gear )
Calculated Ratio Transmission Gear Speedo Gear
0.94 18 17
1.00 17 17
1.00 18 18
1.06 16 17
1.06 17 18
1.06 18 19
1.11 18 20
1.12 16 18
1.12 17 19
1.13 15 17
1.17 18 21
1.18 17 20
1.19 16 19
1.20 15 18
1.21 14 17
1.22 18 22
1.24 17 21
1.25 16 20
1.27 15 19
1.28 18 23
1.29 14 18
1.29 17 22
1.31 13 17
1.31 16 21
1.33 15 20
1.33 18 24
1.35 17 23
1.36 14 19
1.38 13 18
1.38 16 22
1.40 15 21
1.41 17 24
1.42 12 17
1.43 14 20
1.44 16 23
1.46 13 19
1.47 15 22
1.50 12 18
1.50 14 21
1.50 16 24
1.53 15 23
1.54 13 20
1.55 11 17
1.57 14 22
1.58 12 19
1.60 15 24
1.62 13 21
1.64 11 18
1.64 14 23
1.67 12 20
1.69 13 22
1.70 10 17
1.71 14 24
1.73 11 19
1.75 12 21
1.77 13 23
1.80 10 18
1.82 11 20
1.83 12 22
1.85 13 24
1.89 9 17
1.90 10 19
1.91 11 21
1.92 12 23
2.00 9 18
2.00 10 20
2.00 11 22
2.00 12 24
2.09 11 23
2.10 10 21
2.11 9 19
2.12 8 17
2.18 11 24
2.20 10 22
2.22 9 20
2.25 8 18
2.30 10 23
2.33 9 21
2.38 8 19
2.40 10 24
2.43 7 17
2.44 9 22
2.50 8 20
2.56 9 23
2.57 7 18
2.62 8 21
2.67 9 24
2.71 7 19
2.75 8 22
2.86 7 20
2.88 8 23
3.00 7 21
3.00 8 24
3.14 7 22
3.29 7 23
3.43 7 24

  Information credit:
I recently found this chart that I had typed up from 'somewhere' several years ago. The only reference I have to the chart's creator is the name Mr. P Coxe. I do not know the original source, but I do remember typing it all into an excel spreadsheet so I could use it in my shop. I present it for your use. Seeing as I did the typing a long time ago and have no way to confirm the accuracy anymore, some errors may be in here that the original creator did not make. e.g., my mistake, not his.... ok?


Electronic pages by Al

Last Updated on 10/18/97
By Al McKenzie