> How would the 166# current rate translate into coil-over terms? Since it
> appears that the spring is around the shock and strut that it is a
> one-to-one ratio, and a true 166#? Or is there a leverage working there?
I thought a spring is a spring is a spring... so no matter how long or what
diameter or what size the spring is, a 166# rate on an OEM spring would
compress the same rate as a coil over 166# spring.
For a strut suspension, there shouldn't be any leverage going on since the
strut and spring move in a linear relation to each other.
> The "coil-over guy" said that to get a similar rate I would have to go
> to something around 300#!
If you lower it like most coil over suspensions do, well yeah, you would
need to increase the rate. But, if you're going to keep the same ride
height, you shouldn't have to increase the rate. Disclaimer: this probably
varies a lot from spring to spring because of lengths and spring travel
before binding.
Something else to take into consideration with many stock suspensions is the
addition of the bump stop into the true rate of the suspension. A stock
Ford Probe GT comes with 190# springs up front, but that rate is only
experienced for the first part of the travel. At a certain point, the bump
stop rate (progressive) adds into the coil spring rate to give an increasing
rate. The effect on comfort: a smooth ride on small bumps, a rough ride on
big bumps. The effect on handling: wishy-washy during the low rate with a
somewhat harsh and fast transition to the high rate.. not good.
Ideally, you would have one rate springs and not have to use bump stops. If
you have height-adjustable coil-overs, then adjusting the height also
adjusts the additive rate of the bump stop. Car sits too high, you can coil
bind; car sits too low, you're riding on the bump stops.
Most people going with coil over suspensions do them for either lowering
purposes or handling purposes. In both cases, you're probably going to be
increasing the rate compared to the stock spring, hence the answer the
"coil-over" guy gave you. I've always thought it would be fun to put some
12" long 100lb springs on my car to make it ride like a Cadillac. But for
handling purposes, stuff in the 300-400lb range is common on autox cars.
Didn't somebody once say that you want the stiffest springs possible that
the track surface will allow?
Now, you're more confused right?
Brian
--
Brian Berryhill
http://www.angelfire.com/ms/brianberryhill/
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