what rate springs for coilovers

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with the shock fully extened I snugged the adjuster to the spring .does it matter if I have a 14"coil on the bottom and a 12" on top . the adjuster sits 3.5 inches down form the top of the threads
 
I was wrong the weight is 1370 per corner I forgot to carry a number yes I am a jackass so now what should I do for spring weights
 
even if we nicely assume you have a 60/40 split in weight, it's still a 5000# estimate...and I hve a very hard time believing that's accurate.

weigh it....please....

Have you called your supplier for the coilovers/springs and talked with them? The good vendors are experts in setting these up, and should be able to assist you with your rate decisions. Many even have calculation sheets that should be pretty accurate.


They will insist on a weight too...weight it....

I was out with Troy in Attica when he was testing his comp buggy...changed coilover rates 4 times in the rear one afternoon, trying to find the sweet spot for verticles. Lots of seat-of-the-pants science if you really want it to perform at it's best.

what time does the local scale open today??
 
FJ40Dude75 said:
I was wrong the weight is 1370 per corner I forgot to carry a number yes I am a jackass so now what should I do for spring weights
Click to expand...


Ok, here's what you need to do since you are obviously not going to go get it weighed. :doh:

Keep ordering springs and returning them until you get where you want to be. Without an actualy weight, not some mathematically imputed number based on your assumptions, you CANNOT get the spring rates figured out by using an internet forum.

To know where to start on what to order, since you have been on the "too much" end, shoot way lower, like 175 over 125 and see where that gets you instead if incrementally working down.

I now think I understand what you meant when you said you made "sick" stuff in your other thread. I took it in a different way than you must have meant it. :D



Ed
 
FJ40Dude75 said:
14"travel it sits at 8.5" when I let the truck down its completed and all the weight is on it I thought with 500lbs of springs that sank 5.5 inches it would work out to @1600 at each front corner am Is that wrong
Click to expand...

yes that is wrong. you are just tossing out number and doing the math wrong. Go here: http://www.swayaway.com/Suspension Frameset.htm

First by having a dual rate spring (200 over 300) you are not at a 500lb spring rate. The formula is:

Primary SPring Rate = (main spring rate * tender spring rate) / (main spring rate + tender srping rate)

For your setup:

(300*200) / (300+200) which is 60000 / 500 = 120 lb spring rate

Seems unreal, but think of it this way....if you have a know weight on the spring say 1000 lbs a 500lb spring will lower 2". Now take your springs and stack them and place the 1000lb on them...the 300 lbs spring lowers 3.333", AND the 200 lbs spring lowers 5", for a total of 8.333". NOT THE SAME AS THE 500 single spring!

Now if your shocks were mounted straight up and down and all the weight equally pushing the spring your 5.5" of lowering would be a 660 lb corner weight (spring rate * inches lowered) = weight. Now this is the SPRUNG CORNER WEIGHT, and doesn't account for wheel, axle, tires, half of the springs and weight of the coils.

But the above is not totally correct as that doesn't that into account where the shock is mounted in relation to the lever arm (link), the angle its mounted at, and the sprung wheel weight (corner weight - unsprung corner rate)

NOW>>>>
Spring selection will be a guessing game some time, because you do want to tune this thing. I would get the vehicle weighed, and establish corner weights. Measure the angles and mounting of the shocks on the links (look at website above). Then determine what your desired ride height is, and how much up travel and down travel you want (articulation) and mount the shocks accordingly. Then we will be able to help you try and get much closer on your selection of springs. Pics of your setup and final mounting of springs will help a ton.

More work needed, come back with the above. :idea:
 
thank you I will get the brakes finished today and try and get a weight
 
cruiserrg said:
yes that is wrong. you are just tossing out number and doing the math wrong. Go here: http://www.swayaway.com/Suspension Frameset.htm

First by having a dual rate spring (200 over 300) you are not at a 500lb spring rate. The formula is:

Primary SPring Rate = (main spring rate * tender spring rate) / (main spring rate + tender srping rate)

For your setup:

(300*200) / (300+200) which is 60000 / 500 = 120 lb spring rate

Seems unreal, but think of it this way....if you have a know weight on the spring say 1000 lbs a 500lb spring will lower 2". Now take your springs and stack them and place the 1000lb on them...the 300 lbs spring lowers 3.333", AND the 200 lbs spring lowers 5", for a total of 8.333". NOT THE SAME AS THE 500 single spring!

Now if your shocks were mounted straight up and down and all the weight equally pushing the spring your 5.5" of lowering would be a 660 lb corner weight (spring rate * inches lowered) = weight. Now this is the SPRUNG CORNER WEIGHT, and doesn't account for wheel, axle, tires, half of the springs and weight of the coils.

But the above is not totally correct as that doesn't that into account where the shock is mounted in relation to the lever arm (link), the angle its mounted at, and the sprung wheel weight (corner weight - unsprung corner rate)

NOW>>>>
Spring selection will be a guessing game some time, because you do want to tune this thing. I would get the vehicle weighed, and establish corner weights. Measure the angles and mounting of the shocks on the links (look at website above). Then determine what your desired ride height is, and how much up travel and down travel you want (articulation) and mount the shocks accordingly. Then we will be able to help you try and get much closer on your selection of springs. Pics of your setup and final mounting of springs will help a ton.

More work needed, come back with the above. :idea:
Click to expand...

Rueben has the correct info. This is what I went through when I had my springs installed. I had the vendor (Lee at www.raceshock.com) walk us through the exercise and the second set of springs had the correct rate. I think this is the best way to
determine exactly how much weight your springs "see" since there are just too many variables due to mounting.
 
When I got my springs from poly performance I kinda guesed on the rig weight. Then ordered a single spring per shock.


Mounted the spring and set the ride height at what I wanted using the adjuster.

Then I called Dave and gave him the amount the single 350lb spring compressed.

He played with some sort of calculator and gave me a second spring amount.

Then to get the ride height I needed he suggested using a 14" spring (16" travel shock) and a spring tender. (if you need to have your truck sit lower then adjust the spring reataining thingie AND get a spring tender so that the shorter spring that you have does not cause issues.. )

Make sense?

where did you buy the coilovers?
 
vintage and high performance found them in the vendor section of pirate .great deal and nice to deal with but dont know much about them but he will swap springs with me
 
Find A Guy That Is Competitive In Local circle Track Racing, He Will Have A Portable Set Of Scales And Pay Him To Come And Weigh The Rig, They Have 4 Pads That Each Tire Sit On.
Butch
 
okay just talked with the guys from poly performanc and they got me straitend out.the collars were hitting the poly bushing in the middle now it sits right and they said my spring rates are good but I did need some spring tenders .now I just need to know where to adjust the adjusters to not the top one just the 2 in the middle of the shock .where should they be ?
 
FJ40Dude75 said:
okay just talked with the guys from poly performanc and they got me straitend out.the collars were hitting the poly bushing in the middle now it sits right and they said my spring rates are good but I did need some spring tenders .now I just need to know where to adjust the adjusters to not the top one just the 2 in the middle of the shock .where should they be ?
Click to expand...
Mount them 3" above the lower coil collar....
 
thanks mace I got some new pics I am still trying to figure out resizeing when I do I will post them
 
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