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Motion Ratio Formula:
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The Suspension Motion Ratio (MR) is a key parameter in vehicle suspension design that represents the ratio of wheel displacement to spring displacement. It affects the effective spring rate and damping characteristics of the suspension system.
The calculator uses the motion ratio formula:
Where:
Explanation: The motion ratio determines how wheel movement is transferred to spring movement, influencing the suspension's leverage ratio and effective spring rate.
Details: Understanding motion ratio is crucial for proper suspension tuning, as it affects ride quality, handling characteristics, and the effective spring and damping rates experienced at the wheel.
Tips: Enter both displacement values in millimeters. Ensure measurements are taken at the same suspension travel point and that both values are positive numbers greater than zero.
Q1: What is a typical motion ratio value?
A: Motion ratios typically range from 0.4 to 1.2 depending on suspension design, with most passenger cars having values between 0.7-1.0.
Q2: How does motion ratio affect spring rate?
A: The effective spring rate at the wheel is calculated as: (Spring Rate) × (Motion Ratio)². A lower motion ratio reduces the effective spring rate.
Q3: Can motion ratio change through suspension travel?
A: Yes, in many suspension designs the motion ratio is not constant and varies throughout the suspension travel, which is known as rising rate or falling rate suspension.
Q4: How do I measure displacement values accurately?
A: Use precise measuring tools and ensure the vehicle is on a level surface. Measure wheel movement at the center of the wheel and spring movement at the spring mounting points.
Q5: Does motion ratio affect damping characteristics?
A: Yes, similar to spring rate, the effective damping at the wheel is calculated as: (Damper Rate) × (Motion Ratio)².