effective spring rate calculations for standard shocks
10-29-2008, 10:08 AM
#1
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effective spring rate calculations for standard shocks
Okay, I know the formula for determining effective rear spring rates for a coilover with T-bars.
Is the equation the same for a standard shock and t-bar setup, as opposed to a coil over shock?
If not, what is different?
TIA
Is the equation the same for a standard shock and t-bar setup, as opposed to a coil over shock?
If not, what is different?
TIA
10-29-2008, 12:30 PM
#2
Nordschleife Master
Not the same, here you go:
(Take into account that the effective spring rates for the hollow bars produced by some aftermarket firms are different to those below. The manufacturer should provide the effective rates for the hollow bars)
(Take into account that the effective spring rates for the hollow bars produced by some aftermarket firms are different to those below. The manufacturer should provide the effective rates for the hollow bars)
10-29-2008, 12:50 PM
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okay. I already have those numbers. My question isn't the T-bar value.
My question is whether the equation is the same for a standard shock plus t-bars, as opposed to a coil over shock plus t-bars. The t-bars are a constant.
Is there a difference in calculation between say a bilstein HD shock and x brand coil over shock, if the "spring rate" is the same for both the shock and the coil over?
My question is whether the equation is the same for a standard shock plus t-bars, as opposed to a coil over shock plus t-bars. The t-bars are a constant.
Is there a difference in calculation between say a bilstein HD shock and x brand coil over shock, if the "spring rate" is the same for both the shock and the coil over?
10-29-2008, 01:26 PM
#4
Nordschleife Master
Shocks are not springs, they do not have a "spring rate", or if you want the spring rate is zero.
Shocks are only there to dampen the spring so that you don't bounce down the road forever.
Shocks are only there to dampen the spring so that you don't bounce down the road forever.
10-29-2008, 02:08 PM
#5
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That means that a shock provides some rebound and compression number combined with the rate of the t-bar. They work in concert.
Therefore there IS an "effective" or calculable "rate" of the shock component.
How is that derived?
Get it?
10-29-2008, 02:28 PM
#6
Nordschleife Master
Nope, the damper contibutes nothing to the spring rate. Whatever your t-bar effective rate is from the table above will be the effective rate at the wheel.
I think you are confusing yourself here, I shall try to explain:
Springs are really shock absorbers in their real sense. They absorb the shocks from the road.
Shocks are just dampers, they "dampen" the spring to stop it bouncing.
If you ever drive a car with bad shocks you will see that the springs do their job just fine, they absorb the shocks from the road as they always did. Its just that the car will not stop bouncing, and that is because the shocks (or dampers) are not dampening the spring in rebound or compression to stop it from moving up and down.
So, if your replace your standard shocks with HD ones, or with ones with a different valving for compression and rebound, you will still maintain the same effective rate as before (derived from the rate of your t-bars). The only thing the upgraded shocks will do is make the spring come to rest faster = less bounce and the spring is ready faster for the next movement. Hope this helps.
BTW: I'm not one of these: "Don't believe everything you read on rennlist. For every 15 opinions one of them actually has some experience."
But someone else might want to chirp in here to confirm the relationship between springs and shocks.
.
I think you are confusing yourself here, I shall try to explain:
Springs are really shock absorbers in their real sense. They absorb the shocks from the road.
Shocks are just dampers, they "dampen" the spring to stop it bouncing.
If you ever drive a car with bad shocks you will see that the springs do their job just fine, they absorb the shocks from the road as they always did. Its just that the car will not stop bouncing, and that is because the shocks (or dampers) are not dampening the spring in rebound or compression to stop it from moving up and down.
So, if your replace your standard shocks with HD ones, or with ones with a different valving for compression and rebound, you will still maintain the same effective rate as before (derived from the rate of your t-bars). The only thing the upgraded shocks will do is make the spring come to rest faster = less bounce and the spring is ready faster for the next movement. Hope this helps.
BTW: I'm not one of these: "Don't believe everything you read on rennlist. For every 15 opinions one of them actually has some experience."
But someone else might want to chirp in here to confirm the relationship between springs and shocks.
.
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10-29-2008, 02:45 PM
#8
Nordschleife Master
10-29-2008, 03:17 PM
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Thanks man. It looks like I'll end up going with Escort cup rears and I'll have bilstein re-valve them to balance with the Firehawk fronts.
I intend to run without t-bars, so this was an important factor. I'm looking to go about 300# effective front and rear.
I intend to run without t-bars, so this was an important factor. I'm looking to go about 300# effective front and rear.
10-29-2008, 03:45 PM
#11
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If you're talking about the "dampening rate" of the shock, this is best determined on a shock dyno.
There is an "optimum range" of dampening per spring rate. I told Bilstein what spring rates I was going to run and what the weight of the car is. They then "valved the shocks to match". But I don't know what those values were or even what units they are measured in.
As far as a "motion ratio" - the ratio between wheel movement and shock movement - I believe that would apply to both "spring rates" and dampening rates.
There is an "optimum range" of dampening per spring rate. I told Bilstein what spring rates I was going to run and what the weight of the car is. They then "valved the shocks to match". But I don't know what those values were or even what units they are measured in.
As far as a "motion ratio" - the ratio between wheel movement and shock movement - I believe that would apply to both "spring rates" and dampening rates.
10-29-2008, 04:05 PM
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If you're talking about the "dampening rate" of the shock, this is best determined on a shock dyno.
There is an "optimum range" of dampening per spring rate. I told Bilstein what spring rates I was going to run and what the weight of the car is. They then "valved the shocks to match". But I don't know what those values were or even what units they are measured in.
As far as a "motion ratio" - the ratio between wheel movement and shock movement - I believe that would apply to both "spring rates" and dampening rates.
There is an "optimum range" of dampening per spring rate. I told Bilstein what spring rates I was going to run and what the weight of the car is. They then "valved the shocks to match". But I don't know what those values were or even what units they are measured in.
As far as a "motion ratio" - the ratio between wheel movement and shock movement - I believe that would apply to both "spring rates" and dampening rates.
I'm going with a rear coil over. I'm going to talk to bilstein about matching my valving up front and rear to best fit my spring rates. This will be a pure street set up, so I'm going to go a bit softer than my straight Escort Cup set up, that I have on my '86.
