DanDombrowski
03-03-2004, 09:53 PM
I've seen a lot of people post threads about "what kind of springs should I get if I don't want a harsh ride?", so I thought I would chime in with what I know about them. Now, I have no real world experience with different aftermarket spring setups, so I'm no expert on this, but here goes.
Being a mechanical engineering student, we learn about these "Spring-Mass-Damper" systems in our differential equations class, and it turns out they can be modeled pretty easily. I won't go into actually solving the equation, I'll just skip to the end. Basically, the constants in the system are the mass (weight supported by a spring), spring constant (stiffness of spring), and the damping coefficient (shock stiffness). By changing these inputs, you can make the system behave one of 3 ways.
Underdamped - the damping of the shock is too low, and the system will oscillate with lower and lower magnitude until coming to rest. This is seen when a car has old or bad shocks. As the car goes over a bump, it goes up and down a few times before coming to rest.
Critically damped - this is the longest response time to bring the car back to its original position WITHOUT bieng underdamped. This is what most car manufacturers design for, as it offers the best compromise between ride quality and system response (system response is engineer talk for bringing the car back to normal ride height).
Overdamped - too much damping, very short response time.
All that bieng said, if you want to change your springs and put lower (which often = stiffer) springs, but want to keep a decent ride quality, you want to keep the critical damping the car was designed for, or better yet, find springs that will lower the ride height yet keep the same spring stiffness as before.
the critical damping, C = 2 sqrt(spring constant*mass per wheel). End result - you get the spring constants of the springs you're ordering, plug em into the equation, and call up your shock company and give em the value you're looking for. This won't make the ride as smooth as stock by any means, but you will have a much better and more predictable response. If you're REALLY good, you can plot the responses of different spring applications in math software like MatLab and see what different springs will do to your rebound.
Sorry if this sounds like a math lesson, but I figured that if it helps one of you out somewhere down the road, its worth it.
Being a mechanical engineering student, we learn about these "Spring-Mass-Damper" systems in our differential equations class, and it turns out they can be modeled pretty easily. I won't go into actually solving the equation, I'll just skip to the end. Basically, the constants in the system are the mass (weight supported by a spring), spring constant (stiffness of spring), and the damping coefficient (shock stiffness). By changing these inputs, you can make the system behave one of 3 ways.
Underdamped - the damping of the shock is too low, and the system will oscillate with lower and lower magnitude until coming to rest. This is seen when a car has old or bad shocks. As the car goes over a bump, it goes up and down a few times before coming to rest.
Critically damped - this is the longest response time to bring the car back to its original position WITHOUT bieng underdamped. This is what most car manufacturers design for, as it offers the best compromise between ride quality and system response (system response is engineer talk for bringing the car back to normal ride height).
Overdamped - too much damping, very short response time.
All that bieng said, if you want to change your springs and put lower (which often = stiffer) springs, but want to keep a decent ride quality, you want to keep the critical damping the car was designed for, or better yet, find springs that will lower the ride height yet keep the same spring stiffness as before.
the critical damping, C = 2 sqrt(spring constant*mass per wheel). End result - you get the spring constants of the springs you're ordering, plug em into the equation, and call up your shock company and give em the value you're looking for. This won't make the ride as smooth as stock by any means, but you will have a much better and more predictable response. If you're REALLY good, you can plot the responses of different spring applications in math software like MatLab and see what different springs will do to your rebound.
Sorry if this sounds like a math lesson, but I figured that if it helps one of you out somewhere down the road, its worth it.