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Unread 12-18-2011, 10:43 AM   #1
Hussler
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Coil spring rates, what to look for?

If I want the Jeep to act the same way it does stock, how do I calculate an increase in spring rate? I was adding up my Jeep junk, probably weighs 800 lbs more than when it did stock. Lets say hypothetically its evenly distributed, 400lbs added from my CG forward.

I measured the rate of my current springs (either currie or deaver) and they are approximately 160-170 lbs per inch, and ride very nice (but are too short that's why I'm upgrading). What happens when you go too soft a coil?

If I want a 4.5" lift spring do I just get one with a similar rate? Rustys and Rough are pretty close.


Side thought: Why are some coils rated outrageously high? (BDS 240lbs per inch)

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Unread 12-18-2011, 03:48 PM   #2
jsawduste
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What you want is to measure your Spring Frequency rate of the stock springs. Ibs/inch is one part of the math. Then modify the formula to represent the added weight and length.


Goggle "Spring Frequency Rate Automotive" and there will be plenty of information and formulas.


Another good source of info would be Eibach. They have customer tech that can help you with your questions. Have used Eibach tech. on several projects and they always worked well
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Unread 12-18-2011, 10:40 PM   #3
Hussler
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Holy S*** is this what you mean? http://enderw88.wordpress.com/automo...g-rate-theory/
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Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
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Unread 12-19-2011, 06:03 AM   #4
jsawduste
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Yup, it looks worse then it really is though.

If you give Eibach your parameters they can spit out the calculations for you. Likely they have a spring on the shelf that will fit your needs or darn close to it.
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Unread 12-19-2011, 12:43 PM   #5
Hussler
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Eibach offers lift springs? News to me. So I'm guessing my method of taking a spring out of my jeep and applying weight until it compressed 1 inch (did so at 170ish pounds) isn't accurate enough? I found a calculator that helps factor in gauge
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Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
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Unread 12-19-2011, 03:13 PM   #6
jsawduste
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Quote:
Originally Posted by Hussler View Post
Eibach offers lift springs? News to me. So I'm guessing my method of taking a spring out of my jeep and applying weight until it compressed 1 inch (did so at 170ish pounds) isn't accurate enough? I found a calculator that helps factor in gauge
I would not say Eibach makes lift springs per se but they do make a wide variety of coil springs for many applications. Perhaps they might have have an app that would fit your need. If not they can make one.

Your compression test is one valid piece of the puzzle. But only a piece. Other factors such as compression/rebound rates, damping characteristics etc can be factored in. Depends on how good you want to tune the springs in.
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Unread 12-20-2011, 07:57 PM   #7
Hussler
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Hmmm I dont have the ability to test my compression rate, and it appears the rebound is based off the compression.

I guess I'll just hunt around and see how people feel about BDS springs, at 240lbs rate
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Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
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Unread 12-24-2011, 08:29 PM   #8
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Considering that the BDS springs you're looking at are ~80 lbs greater in rate than your stock ones, that'll make for a very STIFF ride up front...you have to consider that the springs are the given ~80 lbs for each side, so you're really increasing the total front capacity by ~160 lbs/in. That's a pretty good deal. I don't know if the front of my CJ is any lighter than yours, being all steel, V8, etc. etc. but I'm putting in coilovers with a 150 lb/in rate. Keep us updated on what you come up with though.
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Unread 12-24-2011, 09:06 PM   #9
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I emailed the BDS rep and he said that the JK 6.5 lift front springs would be exactly what I'm looking for.
JK 6.5" front springs=Gauge 0.625, rate 175, length 21.75
XJ 4.5" front springs=Gauge 0.656, rate 240, length 20.13

They will probably end up landing 5, maybe 5.5 but that's fine. I think I'll order them after christmas
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Originally Posted by chris87xj View Post
Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
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Unread 12-25-2011, 08:21 AM   #10
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Quote:
Originally Posted by Hussler View Post
I emailed the BDS rep and he said that the JK 6.5 lift front springs would be exactly what I'm looking for.
JK 6.5" front springs=Gauge 0.625, rate 175, length 21.75
XJ 4.5" front springs=Gauge 0.656, rate 240, length 20.13

They will probably end up landing 5, maybe 5.5 but that's fine. I think I'll order them after christmas
Im pretty sure JK coils mount differently then XJ coils.
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Unread 12-25-2011, 08:26 AM   #11
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Im pretty sure JK coils mount differently then XJ coils.
Perhaps Blaine will chime in about that. If not you could PM him. Then when your ready to order you will know for sure.
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Unread 12-27-2011, 12:55 AM   #12
Snoopi8321
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Putting it simply unless you do a long arm 4.5 it won't ride as nice. The change in angle on controls arms will cause the bumps to absorb differently and transfer more of the force to the chassis.

As far as springs go for a softer ride lifted you might wanna check rough country. I believe (not 100%) that their spring are 180lbs. The springs with high rates 200+ are designed for HD applications ie steel bumpers with winches strapped to front.

Good luck with you search hope you find a solution.
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Unread 12-27-2011, 10:17 AM   #13
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I bought the BDS 3" coils this summer and slapped them on. It is a stiff ride but i like it. When i take corners at 10-15 mph over what the sign says my jeep doesnt do the gangster lean it just goes. My guess is softer the better for wheeling but if it is also a dd i would want more stiffness.

May i add speed bumps suck with bds coils lol but at the time i ordered them i didnt know much about spring rates ect. I dont think ill ever be able to stuff my front tire into the fenderwell with this much lb/per inch though.
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Unread 12-27-2011, 06:13 PM   #14
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Quote:
Originally Posted by 2doorxj View Post
Im pretty sure JK coils mount differently then XJ coils.
BDS says they mount the same, and suggested them originally when I asked for a softer rate. I will order them soon
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Originally Posted by chris87xj View Post
Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
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Unread 12-27-2011, 06:26 PM   #15
Hussler
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Quote:
Originally Posted by Snoopi8321 View Post
Putting it simply unless you do a long arm 4.5 it won't ride as nice. The change in angle on controls arms will cause the bumps to absorb differently and transfer more of the force to the chassis. .
My 4.5 rides awesome, you need to buy quality parts. Trying to buy as similar as possible springs, just taller so I can get rid of the spacers
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Originally Posted by chris87xj View Post
Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
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