The motion ratio is a lever arm effect of the control arm acting on the spring. If the spring is mounted at an angle, the reduced motion of the spring must also be taken in account.
The motion ratio of a live axle setup is shown here. Over two-wheel bumps, the motion ratio is 1:1. Over single wheel bumps and during body roll, the motion ratio as shown in step 1. The motion ratio is only used for calculating roll resistance, not for suspension frequencies.
All Eibach motorsport springs are tested between 20% and 70% of the spring’s total travel. This spring rate can be measured easily using the following steps:
Example Spring—Standard: 1200.250.0500 (12”Free Length, 2.5”ID, 500lb/in)
Metric: 0300.060.0100 (300mm Free Length, 60mm ID, 100N/mm)