Front Coil Spring Question
#2984071
11/11/21 11:33 AM
11/11/21 11:33 AM
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Joined: Feb 2003
Posts: 4,953 Houston, Texas
TheOtherDodge
OP
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OP
master
Joined: Feb 2003
Posts: 4,953
Houston, Texas
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This is on my 94 Dakota that has 1,800 lbs on the front end with QA1 coil over conversion shocks/springs. I was running 400 lb springs, 10 inch and changed to 300 lb springs , 11 inch. Before making the change, I did basic math (but didn't take into account the spring angle) and the 300 lb spring should have actually been "taller" than the 400 lb spring after being installed. But, once on the truck, that was not the case. I had to crank the spring all the way to the top of the shock body and it still sits about 1/2" to 3/4" lower than it did with the 400 lb springs. I want to get the front end back up a bit to also help with weight transfer. Anyone ever use a "coil spring spacer" to install in between the coils on the bottom most coil to get the height? This way, the spring will still have MOST of it's properties. Or, I can use a spacer that sits between the shock adjustment plate and spring to lift the spring up an inch (QA1 9004-110 Spring Spacer). I don't want to go back to the 400 lb spring. Thoughts and/or experiences?
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Re: Front Coil Spring Question
[Re: TheOtherDodge]
#2989005
11/25/21 01:09 PM
11/25/21 01:09 PM
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Joined: Jan 2003
Posts: 4,711 Moved to N.E. Tennessee
GomangoCuda
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Moved to N.E. Tennessee
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I am not an expert but To accurately calculate this you would also have to take into account the leverage of the control arm. I would not use any kind of spacers between the coils. A spacer under or over the spring would be ok as long as the spring does not coil bind when compressed.
I got treed by DVW. He did a much better explanation of the leverage issue anyway.
Last edited by GomangoCuda; 11/25/21 01:12 PM.
In theory, there is no difference between theory and practice. In practice, there is.
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Re: Front Coil Spring Question
[Re: Moparteacher]
#2989013
11/25/21 01:21 PM
11/25/21 01:21 PM
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Joined: Jan 2003
Posts: 4,711 Moved to N.E. Tennessee
GomangoCuda
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master
Joined: Jan 2003
Posts: 4,711
Moved to N.E. Tennessee
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The coil spring spacer seems like a bandaid for the incorrect spring.
Agree. A longer spring with your desired spring rate is the best option as long as coil bind doesn't come into play.
Last edited by GomangoCuda; 11/25/21 01:24 PM.
In theory, there is no difference between theory and practice. In practice, there is.
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Re: Front Coil Spring Question
[Re: dvw]
#2989018
11/25/21 01:35 PM
11/25/21 01:35 PM
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Joined: Feb 2003
Posts: 4,953 Houston, Texas
TheOtherDodge
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OP
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Joined: Feb 2003
Posts: 4,953
Houston, Texas
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Thanks all! As I mentioned before, I did "basic" math and didn't take into accounts the necessary angles to get exact measurements, since I was only trying to get the reference to each other. The issue is that I run a QA1 "conversion" coil over and they only offer limited springs so either a 10" 400 lb, 10" 350 lb, or 11" 300 lb. Yes, a 350 lb spring sounds like it would be the correct one, but I can't get one, unless someone else makes one that I am not aware of. So, I will most likely just add a spring spacer ( https://www.amazon.com/gp/product/B01MQL6J71/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1) that shims up the spring about an inch from the bottom of the spring perch.
Last edited by TheOtherDodge; 11/25/21 01:39 PM.
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Re: Front Coil Spring Question
[Re: moparx]
#2989057
11/25/21 04:47 PM
11/25/21 04:47 PM
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Joined: Dec 2005
Posts: 11,524 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,524
Fulton County, PA
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Knowing what shocks are on the thing, like a part number, C-C at ride height, etc, would be helpful.
There are no 2.5" ID, 11" springs for a common coil over that I'm aware of. What are the diameters of the springs?
The answer is - typically, you want the lightest spring that will hold the shocks at the desired C-C at ride height without coil binding before the shock is bottomed out, or you run out of threads. If it wants to separate too violently at the hit, control it with the shock. Information on Length At Coil Bind for springs is available from the manufacturer.
I always end up with lighter springs than what the math tells me.
A short spring will have to be heavier than a longer spring to fit in the same space and do the same job. Simply because the long spring will have to be compressed more. Compressing the spring more stores more energy. That helps get the separation at the hit.
Last edited by CMcAllister; 11/25/21 04:50 PM.
If the results don't match the theory, change the theory.
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