What is motion ratio and why is it important?
Motion ratio is the relationship between wheel movement and spring/shock movement. It affects how spring rate translates to wheel rate. A lower motion ratio means the spring rate needs to be higher to achieve the same wheel rate. See also our Tongue Weight Calculator.
How do I measure dimension A and B on my suspension?
Dimension A is measured from the control arm pivot point to directly under the spring centerline. Dimension B is from the pivot point to the ball joint centerline. Use a measuring tape and ensure the suspension is at ride height.
What's the difference between spring rate and wheel rate?
Spring rate is the force required to compress the spring one inch. Wheel rate is the force at the wheel required to move it one inch vertically. Motion ratio converts between these two values.
How does coilover angle affect spring rate calculations?
Angled coilovers reduce the effective spring rate because the spring doesn't work directly vertically. The calculation accounts for this angle to determine the actual spring rate needed.
What spring rate should I choose for street driving vs racing?
Street driving typically uses lower spring rates (100-200 lbs/in wheel rate) for comfort. Racing applications use higher rates (200-400+ lbs/in) for better handling and reduced body roll.
How do I determine my vehicle's corner weight?
Use corner scales or visit a racing shop with scales. Alternatively, divide total vehicle weight by 4 and adjust for weight distribution (front/rear bias and left/right balance). You might also find our Cornering Force Calculator useful.