Enter the total rod length and the length of the crank stroke into the calculator to determine the rod radio.
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Rod Ratio Formula
The following formula is used to calculate the rod ratio of a crankshaft.
RR = PR / CS
- Where RR is the rod ratio
- PR is the piston rod length
- CS is the crank shaft stroke length
Rod Ratio Definition
What is a rod ratio?
A rod ratio is a ratio of the length of a piston rod to the stroke of an engine.
Rod ratios are used to determine the performance or leverage a piston rod has with respect to the crankshaft stroke.
What is a good rod ratio?
Anything above a ratio of 1.57 is considered a good rod ratio, while high-end racing cars can have ratios of 1.75+
How to calculate a rod ratio?
The following example is a step-by-step guide on how to calculate rod ratio.
First, determine the total length of the piston rod. In this example, the piston rode measures a total of 5 inches.
Next, determine the stroke length of the crankshaft. In this case, the stroke length is measured to be 3 inches.
Finally, calculate the rod ratio using the formula above:
RR = PR / CS
RR = 5/3
RR = 1.6666