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Rock Krawler Rear Coils "Sagging"

11K views 41 replies 13 participants last post by  JKGoob 
#1 ·
Installed the Rock Krawler 2-door 3.5" lift about three months ago. Love the performance but, immediately noticed that the rear end sat about 1/2" lower than the front. As it settled, the rear end droop increased to approximately 3/4". Figured the 190 lbs. Ace bumper and 35" Nitto hanging off the back had something to do with it. Since I already had the Ace front bumper and winch, figured I would need to simply add spacers to the mix. Started with a 1", but after a couple more weeks found myself changing them out for 1 3/4"spacers. After several weeks and some off-roading the jeep remains level (1/16" higher in the rear). All measurements were taken with the soft top installed and the rear seat removed. To say the least I am somewhat concerned about reinstalling the hard top this fall.

While out wheeling this past weekend I noticed that the springs, not the bump stops, are now limiting upward travel as the coils stack on top of each other (coil bind?):facepalm:. It is my understanding that fully compressing coils can lead to failure, but that some are made to do just that. Thus, my first question... are Rock Krawler coils designed to "stack"?

Recognizing that spacers are not the solution, I have come to the forum in search of assistance, but, I have not come empty handed... I have verified that the item # on the coils match that of my application. I have also heard that the bow in the coil caused by setting the rear pinon can effectively reduce the spring rate, so I have attached pictures of the coils. I have the correction wedges installed and I measured my pinon at 15º and driveshaft at 17º for a -2º. So what am I missing? Any help is much appreciated.
 
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#3 ·
I was told by RK that all coils not just the dead zone can be collapsed and it wont harm the springs. Here is a strange thing I noticed as well with my 2.5" Rk coils. I noticed I was down a bit in back so I added 1" spacers and it lifted 1" for a few weeks but after that it settled back down to within 1/4" or so of where it was. Not sure if this is a rk quirk or not.
 
#4 ·
That's good to know. I may just leave them as is. Not excited to loose the inch or so of flex, but if its not hurting anytging... As for the spacers that is exactly what I am seeing... good to know it's not just me.

I have thought about going up a spring size in the rear to their 4.5". Figured it would get me sitting where I want and get me off the spacers or at least some of them.
 
#5 ·
To late to edit, so...

My understanding is that the 4.5" rear coils are not only 1" longer, but also have a slightly higher rate (for stability)? Hoping that the combination may be enough to completely eliminate the spacers all together, or at least drastically reduce the size I have on there now.

My thinking is that the replacement of 1 3/4" of solid material for the additional 5/8" wrap of coil would allow for the tire stuffing flex I originally had. Does that seem to make sense? Of course it could backfire and I could end up with so much rake I look like a funny car at the drag strip.

Sounds like a winter mod to me.
 
#6 ·
interesting stuff. i run the 1.5 4dr or now called 2.5 2dr coils on my 2dr with a 1/2 inch rear spacer and the correction wedges. i was also thinking to run a 1 inch 'taller' rear rk coil and removing the 1/2 inch spacer in my setup, along with going to a longer rear shock at the same time. i have no extra weight on the rear other than my 33 inch pizza cutter spare so i can only imagine how it could be worse with a bumper/carrier setup.
 
#8 ·
How much lift did you net in the back with those springs and spacers?
 
#7 ·
I have the RK 3.5" X-factor with 1.5" spacers in the rear I'm running a pretty heavy rig but this seems to have mostly leveled things out. I too have thought about installing their 4.5" rear springs, may be a better solution for all the weight I have in back. Please keep us updated if you decide to go that way.
 
#13 ·
I spoke to RK and as mentioned in other threads, as an existing customer they are willing to work with me on the price of new rear coils. Likely a winter mod, but I will update if and when I make the switch! :thumb:

I have the first gen rear RK coils (top coils touch at ride height) My belief is they are stiffer. That got me thinking ... I have a light weight 2 door. I asked RK if i would benefit with the new coils and they said yes.
Somebody up for a trade ? Lol
Hmmm... I think you might be right. No transitions would imply a heavier rate throughout the entire coil. I am assuming these are the 2.5" 4-door or 3.5" 2-door coils?

@JKGoob

Looking at photo 1, your rear sway bar angle is no good. You definitely need a set of extended links. :beerdrinking:

The target for the rear sway bar is 0 to -5° but there is a little more room to work. I use an angle pro app on my smart phone to measure the angle.

Here I measure my front sway bar, showing 1.2°, the front should be 0 to 5°.
I measured this morning... 29.5° +/- on both sides... Just to make sure I am following you, are you saying that the sway bar may be "pulling down" the rear end of the jeep? It never occurred to me as I figured the sway bar moves freely as a single unit (at least the front feels that way when I disconnect) and only torques if each end is moved in opposite directions... but I am learning as I go here.
 
#10 ·
@JKGoob

Looking at photo 1, your rear sway bar angle is no good. You definitely need a set of extended links. :beerdrinking:

The target for the rear sway bar is 0 to -5° but there is a little more room to work. I use an angle pro app on my smart phone to measure the angle.

Here I measure my front sway bar, showing 1.2°, the front should be 0 to 5°.

 
#11 ·
that photo is an optical illusion :)
 
#21 ·
So, I got home and started looking... appears as though if I lengthen my rear sway bar links, at compression the sway bar is going to contact the brake line bracket... any one else running this set up? I may just go flex the thing first to see how close I am now.
Yes flex it. also make sure your swaybar is not shifted in the bushings.
 
#24 ·
I'm curious what would be considered normal sag over time. I installed mine in March 2015 but have 10000 miles or so and fair amount of offroading.
 
#33 ·
I have 1.5 now 2.5 on a 2 door. Originally welded the rear spring perch extensions in at the same angle as stock which after adjustment pitched them and the spring up. Around january had the artec truss welded in along with their spring perch extension but level with the new axle angle and it looked droppy draws in the rear. I went with the 3.5 springs in the rear and a .75 spacer on the gas tank side to get the back looking right. I added more weight to the rear than the front. It seems the initial lift i had with the up angled perches went away when i corrected when the new perches were welded in.
 
#35 ·
I'd love to see some pics if you got 'em... my first thought was that the stock perches, even with the wedges, were still off enough to reduce the spring rate. I attached some pics at the begining of the thread and while they bow a bit, it doesnt look excessive enough to loose 1.75", but I am no expert. I thought that someone might suggest adjusting the perches.
 
#39 ·
So I was close to making a decision in favor of the Rock Krawler 3.5 X-Factor lift and am concerned by this series of posts. I had heard from a vendor that (compared to some other lifts) that RK took into account the fact the people were likely to add heavier bumpers and run larger tires, so their springs were a bit higher than the stated 3.5" to account for that. That doesn't seem to be the case based on what I am reading here.

I shouldn't be spending $2k+ on a lift and end up with sagging rear springs and have to add spacers. What do you all recommend and is there anything that RK is doing about it?

Thanks!
 
#40 ·
I would agree that the RK coils provide more than advertised height, that's certainly not the issue... I see it as more of a weight distribution problem. In my particular case I have a 66 lbs front bumper and 55 lbs winch on the front (121 lbs total) and a 190 lbs rear bumper tire carrier and a 115 lbs wheel/tire on the back (305 lbs total). Add some gear in the back and I get the infamous squatting dog.

Admittedly, I believe (without any scientific testing) the triple rate coils which increase free length and provide a soft ride are also more sensitive to weight than their single rate counterparts, that is at least until they reach their third and heaviest rate.

So, I have come to the following conclusions... leave the 1.75" spacers in which limit upward flex (due to coils stacking solid before engaging the bump stops)... order 4.5" rear coils from RK, which from what I understand are not only longer, but incorporate slightly heavier spring rates for stability... or re-distribute the weight of my rig (spare in the tub, lighter rear bumper, heavier front bumper etc., etc.). Option 1, is really not an option... So, new springs or re-distribution of the weight it will be.
 
#41 ·
maybe look into a different spring, metal cloak duel rate comes to mind just because it is basically a single rate coil at ride height and only uses the second rate when flexing.

I run the RK 2.5 on my 2 door so not bashing them at all, just looking at your specific case they might help.
 
#42 ·
Thanks, I may give them a shot... I intend on calling ACE as I have their pro series front and rear bumpers, and they also install RK lifts at their shop. Figure they may have some thoughts on which springs/lifts can handle their bumper weight. On the other hand, I am beginning to consider putting the Willys on a bit of a diet... bfh front and rear bumpers, spare in the tub, and MCE flexible fenders... I am fully armored underneath, but just cant bring myself to switch to aluminum.
 
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