3 replies to this topic

[Manson]

Maybe a dumb question but is there a ratio of damper rate to spring rate (at the wheel) that designers use for a starting point? Is it a one to one ratio, say 200 lb. damper rate on bump used when the wheel rate is 200 lb.? Right now I'm running less dampening rate to spring rate and wonder if I could use more.

[wegmann]

Originally posted by Manson
Maybe a dumb question but is there a ratio of damper rate to spring rate (at the wheel) that designers use for a starting point? Is it a one to one ratio, say 200 lb. damper rate on bump used when the wheel rate is 200 lb.? Right now I'm running less dampening rate to spring rate and wonder if I could use more.

There's no general answer because it depends on the mass involved - what kind of car are you talking about? To see what I'm talking about, look up the equation for "critical damping" which will help you determine the level of damping which will allow the spring to return fastest to the resting point without going beyond it. That level depends on both the spring rate and mass that is oscillating.

From there, it becomes application-dependent and there's plenty of people on this board who can help you. I am not one of them.

[Manson]

The total weight of the car with driver is 870 lb. Spring rates vary from 150-225 lb. The static weight distribution is 66% left side for the ovals.

approx. without driver

RF 110 lb.
LF 235 lb.
RR 160 lb.
LR 230 lb.

[Greg Locock]

For a production car we'd use about 2-6 N/mm/s as our initial damper setting (near zero), with a spring rate of about 40 N/mm

A race car for smoothish circuits willl need MUCH more than this. Milliken in section 22.4 works out an optimum damping of 45% of critical for a racing car