How To Calculate Motion Ratio

Motion Ratio Formula:

\[ MR = \frac{\text{Lever Arm Wheel}}{\text{Lever Arm Spring}} \]

Motion Ratio (MR):

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1. What is Motion Ratio?

Motion Ratio (MR) is a key parameter in suspension design that describes the relationship between wheel movement and spring movement. It's calculated as the ratio of the lever arm at the wheel to the lever arm at the spring.

2. How Does the Calculator Work?

The calculator uses the Motion Ratio formula:

\[ MR = \frac{\text{Lever Arm Wheel}}{\text{Lever Arm Spring}} \]

Where:

Lever Arm Wheel — Distance from pivot point to wheel connection point (mm)
Lever Arm Spring — Distance from pivot point to spring connection point (mm)

Explanation: The motion ratio determines how much the spring compresses relative to wheel movement, affecting suspension stiffness and ride characteristics.

3. Importance of Motion Ratio

Details: Motion ratio is crucial for calculating wheel rate, tuning suspension characteristics, and ensuring proper suspension geometry in automotive and mechanical applications.

4. Using the Calculator

Tips: Enter both lever arm measurements in millimeters. Ensure accurate measurements from the pivot point to the respective connection points for precise results.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical motion ratio value?
A: Motion ratio typically ranges from 0.5 to 1.5, with values around 1.0 being common in many suspension designs.

Q2: How does motion ratio affect suspension stiffness?
A: A higher motion ratio increases effective spring rate at the wheel, making the suspension feel stiffer, while a lower ratio reduces effective spring rate.

Q3: Can motion ratio change during suspension travel?
A: Yes, in many suspension designs the motion ratio is not constant and changes throughout the suspension travel, creating progressive suspension characteristics.

Q4: How is motion ratio related to wheel rate?
A: Wheel rate = Spring rate × (Motion ratio)². The motion ratio squared relationship means small changes significantly affect wheel rate.

Q5: Should motion ratio be considered when changing springs?
A: Absolutely. When changing springs, the motion ratio must be considered to calculate the actual effect on wheel rate and suspension behavior.