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Coil Springs


JFA_Spyderman

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Yo,
This is kinda going to be a re-post. I asked this same question on the old forum, and because i cant look it up to see what was posted and replied, i am posting the question again. Not only for me, but as i remember there was good infomation in that thread for anyone in the same boat as me.

At my work, we have a special scale for measuring tounge weght. It will measure from 200 up to 3000 lbs. So to help me find the right spring for my truck, i placed it directly under the coil mount on the TTB and got my weight.

1200lbs. passenger side
1300lbs. driver side

Because my future plans may involve more weight, i am going to use the driver side measurement. I also added the future weight of the winch (80lbs.) and the winch bumper (80lbs.). Those added together and then divided evenly between the two sides is 80lbs. So the total so far is 1380lbs.

Using Will's writeup in the tech library as a guide, and knowing that my overall goal is for 6" of lift. I took my 1380lbs./6" = 230PPI X 1.5(TTB factor) = 345PPI.

So to make a short question long... :rolleyes: Does this number look right? Another goal is for around 17"-20" of travel when i am done. I am also having trouble remembering how we found out the proper coil length i would need. Thanks!
 
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4x4junkie

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You need the figure for compressed coil ride height to figure the needed coil free length.

Stock compressed ride height is 10.5-11", so for 6" lift, you'd need coils that sit between 16.5-17" with weight on them.

Remember to subtract the unsprung weight from your figures (approximately 300-350lbs for the axle, tires & wheels), so you'd have somewhere in the neighborhood of 2460lbs sprung weight.

6-7" seem to be the ideal range of spring compression on the RBV TTB, so to get that, you'd need a coil somewhere between 265-305 PPI.

2460lbs ÷ 2 = 1230lbs
1230lbs × 1.5 = 1845lbs
1845lbs ÷ 6" = 307.5 PPI
16.5" + 6" = 22.5" free length needed

OR

2460 ÷ 2 = 1230
1230 × 1.5 = 1845
1845 ÷ 7" = 263.6 PPI
16.5" + 7" = 23.5" free length.


IIRC, it was just mentioned in another post that BC Broncos 6.5" "with winch" coils are 249 PPI, and 23.5" long.
While just a slight tad softer than ideal, I'd bet they'd work pretty well for you with maybe a washer shim or two (or a small spacer).
They'd compress right about 7.4" on your truck.

1845lbs ÷ 249PPI = 7.4" compression
23.5" - 7.4" = 16.1" compressed ride height


Hopefully some of those figures make sense :icon_twisted:
 

JFA_Spyderman

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Yo,
Junkie, that is probably the best explanation i have heard. I'm a numbers-kind-of-guy, so that actually makes a lot of sense to me. Now when i need to reference this page I will be able to search and find it again. I did read the other thread and i am excited to learn what he finds.

I have also got in touch with deaver spring, and they pointed me to Coil Spring Specialties. I am now just waiting on a quote from them before i decide what i am going to do. Thanks again for your help!
 

rickcdewitt

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i need to write that formula down for use with 4" of lift!
 

Brian

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Just to add a little something something to this discussion...

I'm going to be using Skyjacker Part number JC80F (8" XJ Lift Coils on my next Bronco II Build) I purchased them before researching them... Yeah I know but I'll make them work.

They measure out at 23"s free length and I called SkyJacker this morning to get their spring rate. They stated that they were 235lb coils. This was a bit softer then I wanted to go and so I will probably have to shim them up or lower the buckets down slightly to get the 6"s of lift I'm looking for according to the information above that is.
 

4x4junkie

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Last edited:

rickcdewitt

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Brian, I have the JC60F coils in mine, they measure 22" free (don't ask me why), and they sit right about 16.5" loaded (or about 5" lift) on my BII. Try them before you mod anything anyway.

You might compare yours to here
http://www.therangerstation.com/forums/showthread.php?p=24763#post24763
o.k. now i'm confused, 4x4junkie which of your trucks has the 3" lift with the 2" body?(the "too high" thread).also, if i'm reading this thread right i take it you can run 4-5"s with 3" pivot drops?is 5" the max?
 

4x4junkie

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I raised the coil buckets up 2" to be able to run the JC60F coils.

I think I may have mentioned this in the link I posted (look back in the thread a ways).
 

rickcdewitt

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I raised the coil buckets up 2" to be able to run the JC60F coils.

I think I may have mentioned this in the link I posted (look back in the thread a ways).
yes now that you say so i remember about taller springs for lower percentage of travel per spring.
 

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