Understanding Motorcycle Sprocket Ratios

Sprocket ratios are a fundamental element of motorcycle performance. The final drive ratio is determined by dividing the number of teeth on the rear sprocket by the number of teeth on the front (countershaft) sprocket.

How It Works

The ratio affects how power is transferred from your engine to the rear wheel:

  • Higher Ratio (larger rear or smaller front): Increases acceleration and low-end torque.
  • Lower Ratio (smaller rear or larger front): Reduces engine RPM at cruising speed and increases top speed potential.
Example: A 45T rear and 15T front gives a 3.00 ratio (45 ÷ 15). Switching to a 48T rear increases it to 3.20, improving acceleration but reducing top-end speed.

Choosing the Right Setup

  • Track or off-road riders often prefer higher ratios for responsive throttle control.
  • Touring or highway riders may prefer lower ratios for fuel economy and lower RPMs at speed.
  • Changing sprockets may require a new chain or adjustments to chain length and tension.

Gear Ratio Reference Table

The table below provides calculated gear ratios for various front and rear sprocket combinations.

FRONT
R
E
A
R
10 11 12 13 14 15 16 17 18 19
30 3.00 2.73 2.50 2.31 2.14 2.00 1.88 1.76 1.67 1.58
31 3.10 2.82 2.58 2.38 2.21 2.07 1.94 1.82 1.72 1.63
32 3.20 2.91 2.67 2.46 2.29 2.13 2.00 1.88 1.78 1.68
33 3.30 3.00 2.75 2.54 2.36 2.20 2.06 1.94 1.83 1.74
34 3.40 3.09 2.83 2.62 2.43 2.27 2.13 2.00 1.89 1.79
35 3.50 3.18 2.92 2.69 2.50 2.33 2.19 2.06 1.94 1.84
36 3.60 3.27 3.00 2.77 2.57 2.40 2.25 2.12 2.00 1.89
37 3.70 3.36 3.08 2.85 2.64 2.47 2.31 2.18 2.06 1.95
38 3.80 3.45 3.17 2.92 2.71 2.53 2.38 2.24 2.11 2.00
39 3.90 3.55 3.25 3.00 2.79 2.60 2.44 2.29 2.17 2.05
40 4.00 3.64 3.33 3.08 2.86 2.67 2.50 2.35 2.22 2.11
41 4.10 3.73 3.42 3.15 2.93 2.73 2.56 2.41 2.28 2.16
42 4.20 3.82 3.50 3.23 3.00 2.80 2.63 2.47 2.33 2.21
43 4.30 3.91 3.58 3.31 3.07 2.87 2.69 2.53 2.39 2.26
44 4.40 4.00 3.67 3.38 3.14 2.93 2.75 2.59 2.44 2.32
45 4.50 4.09 3.75 3.46 3.21 3.00 2.81 2.65 2.50 2.37
46 4.60 4.18 3.85 3.54 3.29 3.07 2.88 2.71 2.56 2.42
47 4.70 4.27 3.92 3.62 3.36 3.13 2.94 2.76 2.61 2.47
48 4.80 4.36 4.00 3.69 3.43 3.20 3.00 2.82 2.67 2.53
49 4.90 4.45 4.08 3.77 3.50 3.27 3.06 2.88 2.72 2.58
50 5.00 4.55 4.17 3.85 3.57 3.33 3.13 2.94 2.78 2.63
51 5.10 4.64 4.25 3.92 3.64 3.40 3.19 3.00 2.83 2.68
52 5.20 4.73 4.33 4.00 3.71 3.47 3.25 3.06 2.89 2.74
53 5.30 4.82 4.42 4.08 3.79 3.53 3.31 3.12 2.94 2.79
54 5.40 4.91 4.50 4.15 3.86 3.60 3.38 3.18 3.00 2.84
55 5.50 5.00 4.58 4.23 3.93 3.67 3.44 3.24 3.06 2.89
56 5.60 5.09 4.67 4.31 4.00 3.73 3.50 3.29 3.11 2.95
57 5.70 5.18 4.75 4.38 4.07 3.80 3.56 3.35 3.17 3.00
58 5.80 5.27 4.83 4.46 4.14 3.87 3.63 3.41 3.22 3.05
59 5.90 5.36 4.92 4.54 4.21 3.93 3.69 3.47 3.28 3.11
60 6.00 5.45 5.00 4.62 4.29 4.00 3.75 3.53 3.33 3.16
61 6.10 5.55 5.08 4.69 4.36 4.07 3.81 3.59 3.39 3.21
62 6.20 5.64 5.17 4.77 4.43 4.13 3.88 3.65 3.44 3.26

Use the table to compare different gear setups. For example, a 14/42 ratio (rear/front) is 3.00. Changing to 14/44 gives a higher ratio of 3.14, offering more acceleration.

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