JKS JSPEC suspension kit

[Fargo]

I think JKS says they get 3" of height with a stock Jeep. Others don't really say how they measure it. I think AEV/Nth used to say 3" on a built Jeep. So they always gave a little more lift on a light Jeep.

I don't think you can really do calculations like you can with a linear rate. One of the things I like about JKS though is that they do offer both 2" and 3" so you can mix a match a little to get what you need if you don't want spacers or if you have a heavy front and light rear or something else.

 

[2006TJ1]

This leads me to my next question, Say I decide to get a dual rate spring. My jeep is light (comparatively speaking), so how can I determine which spring to get? I want 3" of lift, but if these spring makers are rating the spring based on a loaded up jeep with heavy bumpers and such, and are tight lipped on spring rates, how can one run the calculation for sprung weight to determine if they are getting the right length spring? If I order 3" springs and I net 4" or more, I will not be pleased. So do I order 2" springs and hope for 3" of lift? Do I give said spring maker my sprung weights and let them make the calculations to get me the height I want based on the weight of my rig?

I'm wondering the same thing. I am in the market for some 3" springs, but like you said, I will be very disappointed if my 3" set turns into 4".
I was considering BDS for a while. My plan was to do 3" in the front and 2" in the rear. Maybe I'll mix and match them in the suspension kit to avoid a spacer.

 

[bobthetj03]

I'm not a fan of the jeep rake you get, so 3" front 2" rear might be the way to go. Would like to avoid spacers as well. This is why I like OME springs. They are predictable, OME has the specs down pretty accurately, and you have choices. When I installed my OME 2.5" lift many moons ago, I ran the HD spring option 4.0L, hard top, winch up front, and anticipated heavy bumpers/tire carriers and such, but that never happened, so I had some rake back there. Ended up pulling the 10mm spacers in the rear to level it out, and got it close enough to satisfy me. The dual rate spring still intrigues me though. Just wish I didn't have to play a guessing game to get the height I want.

 

[2006TJ1]

I'm not a fan of the jeep rake you get, so 3" front 2" rear might be the way to go. Would like to avoid spacers as well. This is why I like OME springs. They are predictable, OME has the specs down pretty accurately, and you have choices. When I installed my OME 2.5" lift many moons ago, I ran the HD spring option 4.0L, hard top, winch up front, and anticipated heavy bumpers/tire carriers and such, but that never happened, so I had some rake back there. Ended up pulling the 10mm spacers in the rear to level it out, and got it close enough to satisfy me. The dual rate spring still intrigues me though. Just wish I didn't have to play a guessing game to get the height I want.

I have a relatively heavy front bumper and do plan on getting a rear bumper with a hitch built in so I can get rid of the Curt hitch, so that combo should work fine... but like you said: will it end of being 2.5/1.5? or will it be more like 3.5/2.5? I just don't love the idea of ending up above 3" so I am definitely hesitant. When the funds come together, I wouldn't mind being a guinea pig for everyone on here. I did email Justin from JKS who posted earlier, and he said I can purchase a package without shocks (as I just put in some new Ranchos), so if I could also change the setup to 3"/2" and (probably?) ditch the new control arms, I'd be all in.

 

[bobthetj03]

I have a relatively heavy front bumper and do plan on getting a rear bumper with a hitch built in so I can get rid of the Curt hitch, so that combo should work fine... but like you said: will it end of being 2.5/1.5? or will it be more like 3.5/2.5? I just don't love the idea of ending up above 3" so I am definitely hesitant. When the funds come together, I wouldn't mind being a guinea pig for everyone on here. I did email Justin from JKS who posted earlier, and he said I can purchase a package without shocks (as I just put in some new Ranchos), so if I could also change the setup to 3"/2" and (probably?) ditch the new control arms, I'd be all in.

Just had a conversation with Dirk @ DPG Offroad. He sells both JKS and OME, and has given me good advise in the past on other things. What he said made me think, so I'm gonna think about it some more. Based on popular deception, a spring will effect your ride quality to a degree. Josh might chime on this, and @JMT is doing some leg work on this subject. I may end up with some new 2" OME springs and just space accordingly to get the 3" height I want. Don't fear the spring spacer brah.

 

[jjvw]

I played a lot with springs a few years ago. I won't go so far as to say that the springs don't effect the ride quality, but I will say that the differences fall very far on the insignificant side. Shocks are far more important. Here are some things to keep in mind in your search for springs.

First and foremost, find the longest spring that will provide the ride height you are after.

Don't get hung up on progressive vs dual vs triple rate. Focus more more on the final ride height.

Linear rate is easy to predict if you know your sprung weights.

If your springs are providing the ride height you want, but are bottoming out, then you simply need different shock valving to slow the compression. Don't try to fix this with a higher rate spring. Also, make sure that your up travels are what they ought to be.

If you are changing the cargo weight often, a heavier rate spring will change its ride height less than a softer rate will.

Metalcloak springs with their dead coils are a gimmick. Keep the coils live and functioning. If you want to play their game of extreme droop, then use a spacer with the spring of your choice. Adding bump stop to prevent coil bind is dumb.

If you are going to make use of the free length of your springs, then you need to be cycling your suspension so that you know what your limits to droop are. Too much droop can bind a drive shaft.

Up travel is more valuable than down travel.

 

[Fargo]

Just had a conversation with Dirk @ DPG Offroad. He sells both JKS and OME, and has given me good advise in the past on other things. What he said made me think, so I'm gonna think about it some more.

So what was his general advice? I'm going to guess it was to just get a linear spring. It seems that most venders are afraid of progressive springs for some reason.

 

[JMT]

Just had a conversation with Dirk @ DPG Offroad. He sells both JKS and OME, and has given me good advise in the past on other things. What he said made me think, so I'm gonna think about it some more. Based on popular deception, a spring will effect your ride quality to a degree. Josh might chime on this, and @JMT is doing some leg work on this subject. I may end up with some new 2" OME springs and just space accordingly to get the 3" height I want. Don't fear the spring spacer brah.

A controversial topic, but I’m convinced that spring rate does have some effect on ride quality. Of course, that is totally presupposed by the progressive and dual spring marketing, and how much effect is probably quite minor. The butt dyno might be the most objective measurement we can get.

What do you think about the OME 2934?

 

[fuse]

A controversial topic, but I’m convinced that spring rate does have some effect on ride quality.

I know people have strong opinions about springs and ride quality, but I have a hard time understanding how spring rate wouldn't correlate to shock damping. For example, if I swapped a Moog 3227 Rear Spring at 200 lbs/in for an OME Light Duty 2941 Rear Spring at 140 lbs/in, wouldn't that require a corresponding decrease in shock damping?

 

[JMT]

I know people have strong opinions about springs and ride quality, but I have a hard time understanding how spring rate wouldn't correlate to shock damping. For example, if I swapped a Moog 3227 Rear Spring at 200 lbs/in for an OME Light Duty 2941 Rear Spring at 140 lbs/in, wouldn't that require a corresponding decrease in shock damping?

Hence the reason kits are put together to pair shocks and springs. Probably some marketing there, but probably some truth as well. Also, don’t you feel like every time you load your Jeep down it drives softer? What’s the cause of that? Shock valving? Spring rate? Or some combination?

But, ultimately, how many of us are super concerned about our ride quality? Now, getting a particular ride height, and being able to predict it, that’s the real game in town.

 

[Fargo]

I know people have strong opinions about springs and ride quality, but I have a hard time understanding how spring rate wouldn't correlate to shock damping. For example, if I swapped a Moog 3227 Rear Spring at 200 lbs/in for an OME Light Duty 2941 Rear Spring at 140 lbs/in, wouldn't that require a corresponding decrease in shock damping?

It seems to me that such a change would require an increase in compression dampening and a decrease in rebound.

Part of the issue is always subjective preference of what people want in their ride quality. Do you want a more European sports car type of handing with a firm ride or do you prefer the boat like float of a Cadillac. From my reading on various forums most people seem to prefer the cushy Cadillac ride and do not give handling much regard. I seldom see post about how well a suspension handles or behaves on the road. I only hear how cushy it is offroad. Personally I don't want cushy. I want CONTROLED. Take a ride in a new JLUR. Very well controlled. Take a ride in a JKUR with the AEV 2" dual sport with correction brackets and raised trackbar brackets. They are amazing. AEV has a video of one on 35s racing around a race track. Its very impressive. They are also the comfortable and controlled ride you will get offroad.

Back to the subject at hand and how springs and shocks correlate, they certainly do. When I put my BDS 2" lift on I installed Rancho 9000xl adjustable shocks because they came highly recommended by a well respected veteran on the forums. (You know who I mean). But they were terrible with the BDS springs. They had no rebound control. The rear wheels would skip across pot holes and if I hit a shallow wallow in the road the rear of the jeep would spring skyward with uncontrolled rebound. I think the problem was I have a heavyish LJ with a hard top and steel rear bumper. The Jeeps that particular person usually setup would use a much softer dual rate coil and I suspect the Jeeps ran with softtops out in CA. In that setup those shocks likely worked fine. But they did not work well at all with my setup. Then I switched to Bilstein 5160 shocks. A brand of shock that particular person criticizes as being so stiff you can tell if a coin you drove over was heads or tails. But with my LJ and the BDS springs the 5160s were amazing. Suddenly my Jeep suspension was very well controlled. The handling was vastly improved and the ride cush quality was better than the Ranchos on their #3 softest settings. I couldn't believe how such a well respected man could get shock selection so wrong. But I came to the conclusion that it all had to do with different weights of the Jeeps we were working with along with the spring rates required to support that weight and a touch of personal preference. Where I prefer a slow controlled rebound, I believe the individual I speak of prefers a fast er rebound to keep the shocks from packing up in high speed offroad. Something I never do.

So in the end, you really have to figure everything out for yourself and build for your own needs. But its not easy to figure it all out and sometimes takes change in things like springs and shocks.

 

[JMT]

More than that. I'm saying the Nth Degree spring IS the exact same as the AEV springs.

The original Nth Degree Mobility was founded by Jim Frens. Prior to founding Nth Degree Mobility, Jim was a Senior Engineer for Chrysler. Guess which division he worked in... Yeah, he worked with Jeep. He did the engineering on the factory TJ suspension system while he was employed by Jeep. So he obviously knows our TJ suspension well. I think he was constrained at Jeep with what he could do with the TJ suspension, so when he founded Nth Degree he took the engineering the next level, the 'Nth degree' so to speak. He introduced things like progressive rate springs, outboarding the shock mounts, and the rear torque arm Stinger suspension. That was back in 2002. I think the rest of the Jeeping community is just now starting to realize the benefits of some of the things he introduced. (Thats not to say these things never existed in other applications before).

Anyway, it turned out that Jim was a better engineer than he was a business man and Nth Degree ran into financial difficulties. At that point Jim sold Nth Degree to AEV. So the AEV line of TJ products is actually all Nth Degree Mobility. They are one in the same. Not only that, but AEV then hired Jim Frens as the Senior Engineer at AEV. So the entire line of AEV JK suspension was also designed by Jim Frens. So you could say that the AEV JK suspenion is also Nth Degree. They had the same designer.

Jims profile on linkedin shows that he now owns a consulting firm called 'Terrestrial Dynamics Consulting'. I'm not sure what it is exactly he is doing. However, I have seen magazine articles in the past that say AEV worked with Jim while producing the suspension for the Dodge Ram. So it seems he is still doing some work with AEV. I would not be surprised if Jim is being consulted and working with AEV on on the JL suspension. But that is pure speculation.

This is why I am so dissappointed that Nth is no longer available. They were a great product. AEV was built on Nth Degree suspensions.

I really hope someone picks up the rights to the Nth product line. Then that same organization needs to be in contact with AEV to pick up the JK product line when AEV is done with that line. There is a huge business opportunity here. KNowWhere2Jeep saw that opportunity. He was just not able to bring it to its full potential.

Great post. Thanks a lot. Very informative.

 

[jjvw]

Weight absolutely matters. To be systematic in piecing everything together, start with the springs. Do they provide the ride height? Do they give the necessary load support? Do they have the travel to cover the shock travel.

After that, adjust the ride with shocks.

 

[bobthetj03]

A controversial topic, but I’m convinced that spring rate does have some effect on ride quality. Of course, that is totally presupposed by the progressive and dual spring marketing, and how much effect is probably quite minor. The butt dyno might be the most objective measurement we can get.

What do you think about the OME 2934?

I wish I had the time and money to try different springs, but I don't. I don't know if I want to gamble with trying the 2934's. Assuming that is a ZJ front spring? If I decide to go with another linear spring, I think I'll just stick with the the 2933 up front, and maybe go to a 2941 for the rear and add spacers to get 3". Or, take a gamble and try the dual rate JSPEC's. Or, Synergy's? @Fargo posted some info in the other thread about them and I like the spring rates.

 

[fuse]

I wish I had the time and money to try different springs, but I don't. I don't know if I want to gamble with trying the 2934's. Assuming that is a ZJ front spring? If I decide to go with another linear spring, I think I'll just stick with the the 2933 up front, and maybe go to a 2941 for the rear and add spacers to get 3". Or, take a gamble and try the dual rate JSPEC's. Or, Synergy's? @Fargo posted some info in the other thread about them and I like the spring rates.

The nice thing about OME is that they actually publish their spring specs. So at least you can compare them on paper.

2933 - TJ Heavy Front, 19.49" free length, 140 lbs/in.
2934 - ZJ 5.2L Front, 20.08" free length, 160 lbs/in.
2941 - TJ Light Rear, 15.35" free length, 140 lbs/in.
2942 - TJ Heavy Rear, 14.96" free length, 160 lbs/in.

Depending on how front heavy your Jeep is, the 2934 is going to sit about 1" to 1.25" higher than the 2933. Also, depending on how front heavy your Jeep is, the ratio of F/R sprung weight is probably between 1:1 and 0.75:1. For the manufacturers that do publish specs, you see that same ratio in spring rates. Seems like you wouldn't want a higher spring rate in the front than the rear unless you had dramatically changed weight distribution.

Also, the OME 2942 seems too short to pair with the 2934, even though the spring rates are the same. I guess you could try to make up for it with spacers, but it's probably a better idea to start with a matched set of springs.

 

[bobthetj03]

I know 933/942 combo gives me 2" of lift. I keep trying to convince myself to just get a new fresh set of that combo and just add some 1" spacers and call it a day.

 

[skrelnik]

I wish I had the time and money to try different springs, but I don't. I don't know if I want to gamble with trying the 2934's. Assuming that is a ZJ front spring? If I decide to go with another linear spring, I think I'll just stick with the the 2933 up front, and maybe go to a 2941 for the rear and add spacers to get 3". Or, take a gamble and try the dual rate JSPEC's. Or, Synergy's? @Fargo posted some info in the other thread about them and I like the spring rates.

When in doubt call Dirk at DPG again and just tell him what you want and he will deliver by mixing and matching OME coils. That guy knows his suspension and will point you in the correct decision.

It seems to me that such a change would require an increase in compression dampening and a decrease in rebound.

Part of the issue is always subjective preference of what people want in their ride quality. Do you want a more European sports car type of handing with a firm ride or do you prefer the boat like float of a Cadillac. From my reading on various forums most people seem to prefer the cushy Cadillac ride and do not give handling much regard. I seldom see post about how well a suspension handles or behaves on the road. I only hear how cushy it is offroad. Personally I don't want cushy. I want CONTROLED. Take a ride in a new JLUR. Very well controlled. Take a ride in a JKUR with the AEV 2" dual sport with correction brackets and raised trackbar brackets. They are amazing. AEV has a video of one on 35s racing around a race track. Its very impressive. They are also the comfortable and controlled ride you will get offroad.

Back to the subject at hand and how springs and shocks correlate, they certainly do. When I put my BDS 2" lift on I installed Rancho 9000xl adjustable shocks because they came highly recommended by a well respected veteran on the forums. (You know who I mean). But they were terrible with the BDS springs. They had no rebound control. The rear wheels would skip across pot holes and if I hit a shallow wallow in the road the rear of the jeep would spring skyward with uncontrolled rebound. I think the problem was I have a heavyish LJ with a hard top and steel rear bumper. The Jeeps that particular person usually setup would use a much softer dual rate coil and I suspect the Jeeps ran with softtops out in CA. In that setup those shocks likely worked fine. But they did not work well at all with my setup. Then I switched to Bilstein 5160 shocks. A brand of shock that particular person criticizes as being so stiff you can tell if a coin you drove over was heads or tails. But with my LJ and the BDS springs the 5160s were amazing. Suddenly my Jeep suspension was very well controlled. The handling was vastly improved and the ride cush quality was better than the Ranchos on their #3 softest settings. I couldn't believe how such a well respected man could get shock selection so wrong. But I came to the conclusion that it all had to do with different weights of the Jeeps we were working with along with the spring rates required to support that weight and a touch of personal preference. Where I prefer a slow controlled rebound, I believe the individual I speak of prefers a fast er rebound to keep the shocks from packing up in high speed offroad. Something I never do.

So in the end, you really have to figure everything out for yourself and build for your own needs. But its not easy to figure it all out and sometimes takes change in things like springs and shocks.

Great post Fargo!

 

[bobthetj03]

When in doubt call Dirk at DPG again and just tell him what you want and he will deliver by mixing and matching OME coils. That guy knows his suspension and will point you in the correct decision.

Great post Fargo!

I had a conversation with him yesterday when I wanted to pick his brain on the JKS springs. He really didn't have any input on the dual rate springs, suggesting the dual rates don't really add any advantage unless you are going for big lift heights (5-6" and up). He continues to push the OME springs as the best choice to get the ride quality you want. He prefers a more sports car like feel, and I can agree, the 933/942 combo gives you that.

 

[skrelnik]

I had a conversation with him yesterday when I wanted to pick his brain on the JKS springs. He really didn't have any input on the dual rate springs, suggesting the dual rates don't really add any advantage unless you are going for big lift heights (5-6" and up). He continues to push the OME springs as the best choice to get the ride quality you want. He prefers a more sports car like feel, and I can agree, the 933/942 combo gives you that.

That's the same combo he sold to me and I love it. Did you ask him what the 934s would do and what you would need to pair them with, and if it would get you an extra 1" lift over the 933/942 combo?

 

[bobthetj03]

That's the same combo he sold to me and I love it. Did you ask him what the 934s would do and what you would need to pair them with, and if it would get you an extra 1" lift over the 933/942 combo?

No, I didn't. Wasn't thinking about the 934's at the time, but would like to hear his opinion on it.