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Old October 26th, 2009, 07:59 PM   #1
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Default Coilover guru's step in

I'll try to keep it brief.......
I have SAW 2.5 Rem Resi coilovers on the front of my TJ.
I have 14" 350 king springs for my main springs. The vehicle with my winch and some additional weight bring the springs down to 12inches or ~700/corner. This measurement includes being at a 15 deg angle back to vertical.

Space at full droop for springs is 29.25". I have 14" springs, 1" duel slider, 1.5" effective tender slider so 16.5" of height taken up.

I want the vehicle to sit with 5" of shock showing so I need to have 9" of droop. The springs available in 10" are 100, 150, 175, 200, 225.

I'm looking at using a 10" 175lb spring which will put me at an effective rate of 117lb/in. By my calcs, the tender will compress 2.75" initially and the weight of the vehicle will squat the dual rate 5.82" putting me at 8.57" of droop, or 5.4" of shaft showing.
The only 12" spring that would allow me to sit at 5" if I figured right was the 12" 100lb spring which would put my spring rate around 77 lbs/in.

I used the sway away shock calc and foa shock calc but I'm not sure how to use them with a tender and stuff taking up the slack. Also, they suggest alot lighter spring rate(closer to 77lb/in) vs the 117 that I'm looking at. Right now my SUR% will be 300% and I would transition to that with 2" of the shock remaining. So at ride height, I would have 3" of uptravel at 117 lbs, then move to 350 lbs with 2" of shaft remaining.

I'm not sure how to check my frequency with the tender setup. I think I'm supposed to try to calculate it with 14"-2.75" of tender gone initially and use 11.25" shock with the springs I plan on running. Am I on the right track? Here's a copy of the spreadsheet I put together. I have a copy of Johhny J's spreadsheet from pirate but I wasn't able to make other spreadsheets make sense in my head so I made my own. Maybe I'm way off on how I did this too Any insight is appreciated.

I planned on calling Polyperformance and buying springs from them but eibach and king don't make a 175lb spring. I found blue coil springs at www.F-O-A.com that come in a 175lb/in. The rates listed in my spreadsheet are from FOA's website.
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Old October 27th, 2009, 12:35 AM   #2
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i already gave ya the answer...
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Old October 27th, 2009, 09:11 AM   #3
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My guess is you'll find you're fighting the 350 coil, especially with wanting it to work with 65% droop.

I like to run a lower ramp up ratio than what you'll be at to make those 350's work, but it's fine for a first stab.

I don't factor in the keeper spring, it's there just to avoid clanking of springs, so take it out of the equation for spring rate calculations.

In order to get your ~65% droop, you'll need to run the 12" 100 lb spring as your tender spring. That will give you an initial wheel rate of 78 lb/in, and a step up ratio of 450% to the 350 rate. You're going to feel that transition, but like you said, it will be only the last couple inches depending on where you put that transitiion collar.

You might want to consider selling your 14" 350 # springs, check on pirate, there's a whole for sale thread dedicated to selling used C/O springs, so it shouldn't cost you too much. Flat rate box shipping helps for the shorter ones. Most people sell their sets for 75 bucks or less.

IF you are open to changing spring rates, I would suggest a 200/125 rate, which would put the initial rate at ~77, allow for 9" droop at ride height, and give a SUR of 260%.

FOA sells the blue coil springs in 12"x125#.
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Old October 27th, 2009, 09:13 AM   #4
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just to be clear, you are saying you have one of these in your stack? (essentially a triple rate)
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Old October 27th, 2009, 10:10 AM   #5
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just to be clear, you are saying you have one of these in your stack? (essentially a triple rate)
Yes, that is correct. The 1.5" is the thickness of the helper slider including the bottom out material on the opposite side. So with the helper, it's effectively taking up 1.5" block height in the overall package when more than 20 lbs is on the shock.
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Old October 27th, 2009, 10:15 AM   #6
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yeah, so I would still do the 200/125 rate, unless you have to keep the 350 springs.
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Old October 27th, 2009, 10:46 AM   #7
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Most of the TJ builds I've looked at on Pirate are 200/300, which is 120lb/in combined. I've searched and searched.........and now I'm going to search some more .
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Old October 27th, 2009, 11:11 AM   #8
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If that's the case, they are all either:
1) working with heavier rigs (more than 700 lb per corner)
2) not sitting as low as you want with only 5" shock showing at ride height
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Old October 27th, 2009, 11:56 AM   #9
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dont mess with spring rates until it's completely done and loaded ready for the trail.

after it's ready for the trail ask Tab what rates he's running, his is pretty low like you want and his rates seems pretty close from what I've seen...
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Old October 27th, 2009, 12:45 PM   #10
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I threw my winch, and some dead weight on the front when I came up with the 700lb figure. I'm trying to get an approximation so I can keep a look out for springs. Budget gets really tight friday, every penny going forward is going to be thought out .
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Old October 27th, 2009, 12:51 PM   #11
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Quote:
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Budget gets really tight friday, every penny going forward is going to be thought out .
^^^ = keep your eye out for the part out thread
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Old October 27th, 2009, 12:55 PM   #12
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Quote:
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^^^ = keep your eye out for the part out thread
Thanks for the technical advice asshole
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Old October 27th, 2009, 01:09 PM   #13
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Rear weight plays into the front rates and the front weight plays into the rear rates. There is no way to figure actual corner weights until it is done and ready to go.

If you do anything at this point I'd say to copy someone elses setup rather than trying to calculate rates based on unfinished weights.
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Old October 27th, 2009, 01:41 PM   #14
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But then I have to wait..........................oh ok. Kirby IV's TJ runs a 16" 350lb lower spring and a 12" 185lb upper spring with a helper setup at 5" of shaft showing during normal use. I'm fairly close to that with my setup the way I planned it out at this point.
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Old October 27th, 2009, 01:47 PM   #15
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Put the money in a safe place, like in a shoe box burried in the back yard somewhere. That way, when the time comes, you can pick up where you left off and not have to "find" the money again.

Keep an eye out on race-desert.com for used springs.
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Old October 27th, 2009, 01:56 PM   #16
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Originally Posted by feva4u View Post
But then I have to wait..........................oh ok. Kirby IV's TJ runs a 16" 350lb lower spring and a 12" 185lb upper spring with a helper setup at 5" of shaft showing during normal use. I'm fairly close to that with my setup the way I planned it out at this point.
He's got more like 1000# per corner it would seem, and I see you found that pirate thread for used C/Os.

race-dezert and dezertrangers.com are great for finding used coils

I bought my c/o's from a guy on dezertrangers.com
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Old October 27th, 2009, 02:21 PM   #17
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My CO's came with 16" 500lb lowers and 12" 350lb uppers. I traded the lowers for the 14" 350's that I have. I have my 12" uppers for sale currently. I bought helpers and made my own helper sliders. I'll have to check the dezertrangers.com website out. Thanks for the link.
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Old October 27th, 2009, 02:40 PM   #18
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This makes me not want to deal with coil overs

Good tech tho
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Old December 27th, 2010, 02:46 PM   #19
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Update: Using what I planned out in my first post I'm sitting at 7" of shock shaft showing. I don't have fenders on yet but the rest of the weight is pretty much there now. I found out I made my helper sliders 1/4" too short on one side so my helper springs are blocked out. The thinkness of the slider is also 1" compared to the 1/2" that is used with those springs normally so I eliminated .5" of travel that I didn't have to. I'm going to either buy the right ones or modify what I have depending on if I can gather up the tooling needed to modify them.

I'll take pictures tonight, I have a couple questions now. It won't really make sense without pictures.
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Old December 28th, 2010, 08:19 AM   #20
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Yep, didn't take pictures............F. Tonight.
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