12" FOX c/o - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 14 Old 03-15-2017, 04:54 PM Thread Starter
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12" FOX c/o

so i got a good deal from a friend on some 12" fox 2.0 coilover, now i figured out pretty much all the parts i need to set it up. synergy front coilover and air bump mounts, synergy rear coilover + air bump mounts. ill be running the new 40" coopers sst pro with some KMC xd229 machete. now the part im having a hard time with is the Spring rates. some guys run 14'' on the bottom and 12s on top, some guys do 12 and 12, 200 over 300, 250 over 250 heck i even saw 150 over 500... does anyone have a similar set up on their 4 doors? i want the maximum travel but still want it to ride great on and off road!

ive seen a few built 2 doors but not really any built 4doors running a set up similar to mine

its a 2010 JKU Rubicon
it has an evo front bumper and rear carrier that will carry that massive 40"
PS aluminum crusher flares
warn 9.5 cti with synthetic rope
front dynatrac pr44 with rcvs arb and 5.13s
rear is pretty much stock except some ten factory shafts and synergy truss and matching gears of course...
have the RK short arms, will do 3 link front and rear soon...
i always carry over 100lbs or more in tools and spare parts and 350lbs of humans including myself (unless i just go to work)

being north of the border i dont really have access to a specialized shock tuning shop so i just want to have it set up right the 1st time

thanks for any input
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post #2 of 14 Old 03-15-2017, 05:07 PM
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Your plan is to run 40" x 13.5" tires on Dana 44's? How come you don't think that's too much tire for a Dana 44?
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post #3 of 14 Old 03-15-2017, 05:23 PM
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2.0 x 12" travel Fox and King coilovers should have 12" long upper and 14" long lower springs.

Spring rate depends on:
Up travel
Weight
Angles
Emulsion vs Remote Reservoir

-Ryan @
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post #4 of 14 Old 03-15-2017, 05:55 PM
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We usually run 10" uppers and 14" lowers because a 12" upper with 14" lower can be difficult to install.

Spring rate is all about weight and motion ratio, so comparing to other setups won't really do you much good unless the motion ratio is the same. It may take you two shots to get it to where you want it. Just know that once you have springs on there once, you can take measurements to calculate where you want to get to if it isn't right.

For about 4-4.5" of lift to fit 40's, we have had good luck with the following (10" upper over 14" lower):
Front: 350 over 450
Rear: 400 over 500

If you are considerably heavier, your spring rates may need to go up. I wouldn't recommend more than 1-2" of preload to get your ride height where you want it though.

Chris Steimle
Product Manager

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post #5 of 14 Old 03-15-2017, 06:10 PM Thread Starter
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Not for what I do. Ran 37s for the last 6 years and haven't broke anything. I'm not too worried about the front with a pr44 and rcv. Rear should hold up fine. But I guess time will tell.. if it blows I'll do a 60/60 combo but...
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post #6 of 14 Old 03-15-2017, 06:12 PM Thread Starter
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Quote:
Originally Posted by AllJumpStyle View Post
We usually run 10" uppers and 14" lowers because a 12" upper with 14" lower can be difficult to install.

Spring rate is all about weight and motion ratio, so comparing to other setups won't really do you much good unless the motion ratio is the same. It may take you two shots to get it to where you want it. Just know that once you have springs on there once, you can take measurements to calculate where you want to get to if it isn't right.

For about 4-4.5" of lift to fit 40's, we have had good luck with the following (10" upper over 14" lower):
Front: 350 over 450
Rear: 400 over 500

If you are considerably heavier, your spring rates may need to go up. I wouldn't recommend more than 1-2" of preload to get your ride height where you want it though.
Appreciate the input. 400 over 500 in the rear sounds really stiff no?
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post #7 of 14 Old 03-15-2017, 07:05 PM
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Quote:
Originally Posted by RKJK View Post
Appreciate the input. 400 over 500 in the rear sounds really stiff no?
Yea that sounds extremely stiff.

Here's the thing about coilover spring rates. You can usually get it pretty close using calculators and advice from people who do this every day. The only way to get it 100% correct is to install coils and see the results. If it's right it's right. If its wrong, buy more coils. Some companies do a trade in program.

Billet 2013 2 door
Dana 60 front, 14 Bolt rear, ARB's, 5.38's, 40" sticky Trepadors, 3 link front and rear, 14" Sway-a-Way coilovers, Tom Woods 1310 front, Adams 1350 rear, PSC Hydro assist
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post #8 of 14 Old 03-15-2017, 07:16 PM
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Talk to Ryan (TRD) in above post. He can help you get it tuned.
Too many unknowns on your setup to guess at springs. I can tell you what I have on my rigs but I don't have synergy mounts... close out back but not the same up front.
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post #9 of 14 Old 03-16-2017, 09:19 AM Thread Starter
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I stopped at the scales yesterday:

Front weight 3020lbs
Rear weights 2778lbs
For a total weight of 5798lbs

That being said. New wheels and tires are not on and there's no spare on the back. So I'm fairly certain it would be real close to a 6000lbs unit

I will mount the tires on mostly over the weekend and weight it again for more accurate numbers
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post #10 of 14 Old 03-17-2017, 11:33 AM
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Quote:
Originally Posted by RKJK View Post
Appreciate the input. 400 over 500 in the rear sounds really stiff no?
Like I mentioned, spring rates depend on weight and motion ratio. So, unless you are comparing to spring rates from other Synergy coilover setups, it's apples to oranges.

Once you get springs on there and are able to measure sprung weights, it's easy to calculate what springs to get if you need to go lighter or stiffer.

Chris Steimle
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post #11 of 14 Old 03-17-2017, 03:27 PM
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Quote:
Originally Posted by 5.9lj View Post
Talk to Ryan (TRD) in above post. He can help you get it tuned.
Too many unknowns on your setup to guess at springs. I can tell you what I have on my rigs but I don't have synergy mounts... close out back but not the same up front.
This^.

TRD does this for a living, he maaay be able to help.

Kevin
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post #12 of 14 Old 03-17-2017, 03:33 PM
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You can guess but you have good start with your total weights. You need to figure the sprung weight so basically the axles, tires, suspension are going to be your unsprung weight. I have some weights of a dana 60 and 80 with 40's and bead locks but not for dana 44's. If can be found on my build thread at jkfreaks.com. Just a side note, you are likely going to have steering issues running 40's on a stock 44 when with wheel adapters. Performance is going to go way down as well so if you run highway in the hills you are not going to like it.

Once you have the corner weights and the amount of up/down travel you want to have at ride height then you can figure your coil rates. At minimum you want to run the lower coil the same length as the total stroke of the shock if you are running a raised bottom could retainer. If running a flat retainer run the next longer size.

Personal preference may also play a role in your coil rates as if you have a rock crawler you may want a softer coil vs a high speed runner that you may want a higher secondary rate to keep the suspension from bottoming out or rebounding faster. A higher total rate may be better for you if you are running overland and load up with lots of gear and don't want massive amounts of sag in the suspension when loaded up.

Properly setting up coils overs generally take some time and swapping out coils and valving. Do you know what valving you have? How are you planning on running the jeep? Mainly road, rocks, off road speed?

Most people that buy and slap on coil overs are not taking true advantage of what they have to offer. You can have a good ride if you are lucky but if you really want to properly set them up for the best ride, and unless you can find someone that is set up exactly like you are wanting to do that have tuned them, you are not going to find it on the internet. Its going to take some trial and error and how your butt feels in the seat.

Whether you are a 4 door or a 2 door it really does not matter how you choose the coil rates.

Some build info here:
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post #13 of 14 Old 03-17-2017, 03:35 PM
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By the way, what was the "deal" you got from your friend?

Some build info here:
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post #14 of 14 Old 03-17-2017, 04:29 PM
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Thanks guys, I've done a lot of JK's, and a few of them are on my Instagram page: https://www.instagram.com/accutuneoffroad/

Give me a call if you want some help.

-Ryan @
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