Rock Krawler 3-Link Rear Cradle Issue - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 28 Old 05-24-2017, 10:35 PM Thread Starter
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Rock Krawler 3-Link Rear Cradle Issue

I have a confusion regarding the 3-link rear cradle. I noticed that my upper arm is being cut up by the cradle. Now I realize this may be my own problem. The only Rock Krawler product on my rear suspension is the cradle and joints, I made my own arms and used a different solution for the axle side mount. So don't get me wrong, I'm in no way complaining about a product here as I don't have their full kit! But, it sure seems to me that this would also be an issue even if I used the full Rock Krawler kit.

In the photo below, you can see what I'm talking about. On up travel, the arm grinds against the cradle. You can see a bit of a shiny spot on the arm. This is not merely a cosmetic issue. I've already ground away probably 1/16" of my control arm. Eventually, it'll cut all the way through the arm. Control arms obviously should not be a consumable wear item!




The solutions I see are to either basically cut out the cradle and make my own that is much wider, or use a bushing that is self-centering at the frame side and clock the arm to keep it centered in the cradle. Neither is a big deal, I'm just curious how this is supposed to work?
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post #2 of 28 Old 05-25-2017, 02:50 AM
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Is it only touching on one side? Or both?

If only one side, I'd say the mount isn't perfectly straight.

Either way, I'd try to bend the ears of that mount out away from the arm before I broke out the torch.

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post #3 of 28 Old 05-25-2017, 07:11 AM
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like gt1guy said, check all influencing factors like axle center, proper install of the cradle, play in joints, etc.


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post #4 of 28 Old 05-25-2017, 07:41 AM
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As others have stated its a installer error.

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post #5 of 28 Old 05-25-2017, 08:17 AM Thread Starter
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It's only on one side, and it is the side the axle mount is slightly biased towards with respect to the frame cradle.

I don't get how even if everything was perfectly aligned it could work, though. The control arm has a bend in it, so at that region of the control arm, it is free to swing pretty far left and right since both rod ends are not self-centering... no matter how the axle is centered, it would still be prone to rubbing against the cradle as the control arm randomly swings from side to side during motion.
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post #6 of 28 Old 05-25-2017, 08:24 AM
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It is because when you stuff the suspension the axle shifts to the driver side. A self centering bushing is not going to help.You can simply stuff the suspension and shorten the track bar a bit so you have the proper clearance. Otherwise a smaller diameter arm or widen the bracket. You might be able to heat it up and bend the side out a bit as well.

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post #7 of 28 Old 05-25-2017, 08:49 AM
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Can you take a picture from farther out?

Is the bend in the upper link pointing towards the pinion?


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post #8 of 28 Old 05-25-2017, 08:59 AM Thread Starter
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Quote:
Originally Posted by thedirtman View Post
It is because when you stuff the suspension the axle shifts to the driver side. A self centering bushing is not going to help.
If the control arm were straight, I would agree that I could fix it with alignment.

The control arm is bent, such that even suspension stuff I would be able to flop the bent control arm side to side such that it contacts either side of the cradle. Thus, even with an ideal alignment, it can still rub on the cradle. With a self-centering bushing, I would be able to clock it into a position where it does not rub at stuff and it would stay in that position, right?
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post #9 of 28 Old 05-25-2017, 09:07 AM
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Yes if the rubbing is due to turned bent arm a welded self centering end should be used. A threaded end self centered end will typically still rotate at the threads because you are putting bind on the joint when you are flexing allowing the arm to turn.

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post #10 of 28 Old 05-25-2017, 11:37 AM
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Either your truss isn't centered on the axle, the rear axle isn't centered in the vehicle, or the frame side mount is welded in crooked. The arm has a bend in it and the bend orientation is supposed to be straight down toward the ground.

There are no other explanations for what is going on here and it isn't a product fault. One high point here is that the arm is solid steel if it is an RK product.


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post #11 of 28 Old 05-25-2017, 12:15 PM
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It is not an RK arm as the op has stated that and you can clearly see that in the photo.

We all know RK has never, never, ever put out a product that has caused issues because of its poor design or lack of testing..

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post #12 of 28 Old 05-25-2017, 12:25 PM
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LOL Always gotta take your stabs oh Holiness of the JK Fabricators. Get a life bro.

Sorry for the oversight on the arm, but I stand by what I said. Something is out of alignment. What is the OD on the arm that you built?
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post #13 of 28 Old 05-25-2017, 12:56 PM
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Quote:
Originally Posted by christensent View Post
I have a confusion regarding the 3-link rear cradle. I noticed that my upper arm is being cut up by the cradle. Now I realize this may be my own problem. The only Rock Krawler product on my rear suspension is the cradle and joints, I made my own arms and used a different solution for the axle side mount. So don't get me wrong, I'm in no way complaining about a product here as I don't have their full kit! But, it sure seems to me that this would also be an issue even if I used the full Rock Krawler kit.

In the photo below, you can see what I'm talking about. On up travel, the arm grinds against the cradle. You can see a bit of a shiny spot on the arm. This is not merely a cosmetic issue. I've already ground away probably 1/16" of my control arm. Eventually, it'll cut all the way through the arm. Control arms obviously should not be a consumable wear item!




The solutions I see are to either basically cut out the cradle and make my own that is much wider, or use a bushing that is self-centering at the frame side and clock the arm to keep it centered in the cradle. Neither is a big deal, I'm just curious how this is supposed to work?
Sir

Could you post a pic of your axle end and maybe we could help you out some even though it is not our product? Shit happens sometimes when you try to do your own thing. We have a lot of experience with that design. Hopefully we can shed some light on the situation for you..

RK
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post #14 of 28 Old 05-25-2017, 01:03 PM
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Quote:
Originally Posted by thedirtman View Post
It is not an RK arm as the op has stated that and you can clearly see that in the photo.

We all know RK has never, never, ever put out a product that has caused issues because of its poor design or lack of testing..
I guess 10 years of that product being out there is just not long enough huh? Since this has a little bit of DIY in it, maybe you can shed some light on the situation MR. Build Your Own... Why do you have to be that way.. Forums are to help people or at least that is what we think...
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post #15 of 28 Old 05-25-2017, 03:37 PM
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post #16 of 28 Old 05-25-2017, 06:31 PM
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Quote:
Originally Posted by Rock Krawler Suspension View Post
I guess 10 years of that product being out there is just not long enough huh? Since this has a little bit of DIY in it, maybe you can shed some light on the situation MR. Build Your Own... Why do you have to be that way.. Forums are to help people or at least that is what we think...
I was just defending RK everybody knows they make the best suspensions for the jK. Am I wrong? Are you guys putting out stuff that fails?

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post #17 of 28 Old 05-25-2017, 10:17 PM Thread Starter
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Quote:
Originally Posted by RiverCityOffroad View Post
What is the OD on the arm that you built?
1.75" OD

Quote:
Originally Posted by Rock Krawler Suspension View Post
Sir

Could you post a pic of your axle end and maybe we could help you out some even though it is not our product? Shit happens sometimes when you try to do your own thing. We have a lot of experience with that design. Hopefully we can shed some light on the situation for you..

RK
Don't think there's anything particularly important to see here, but this is the rear mount. It is an Artec truss with a mount on top.

Turns out, the mount actually is an inch or more out of being in line with the channel. I put the mount dead center on top of the truss, but apparently that is not lined up with the cradle's center line, did not realize this when I built it. The axle is very well centered in the vehicle, so that's not my issue. I guess I'll cut the mount off the axle and put a new one in an inch over if everyone thinks it'll fix it, not a big deal.



But here's where I'm confused. Below are images showing a cad model of a bent arm in the cradle, at full stuff, with the end points of the control arm perfectly in line with the cradle and constrained to the same point in each picture. The movement of the joints allows the arm to come up at any angle and scrape the sides of the cradle even if everything is perfectly aligned. Is this somehow just not really a problem if the axle side is in alignment with the cradle center line?






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post #18 of 28 Old 05-26-2017, 07:12 AM
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That makes more sense now that you explained what you are running on your rear axle. The Rubicon differential is not centered.


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post #19 of 28 Old 05-26-2017, 08:42 AM
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Quote:
Originally Posted by thedirtman View Post
I was just defending RK everybody knows they make the best suspensions for the jK. Am I wrong? Are you guys putting out stuff that fails?
Not that we know of? Have you seen any of our long arm mounts ever fail? But that is not the point... We gave up on you a long time ago as have many others. It is always better to speak in facts that opinions.

Just for your education - Mid Arm is not our term. It was Jeep he coined the phrase when the JK came out. Not our fancy marketing term.

However, since you don't care to help out this fellow forum member, we will get back to our scheduled programming while you tool around in your custom built JK on 18" King Coil Overs.
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post #20 of 28 Old 05-26-2017, 08:58 AM
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Quote:
Originally Posted by christensent View Post
1.75" OD



Don't think there's anything particularly important to see here, but this is the rear mount. It is an Artec truss with a mount on top.

Turns out, the mount actually is an inch or more out of being in line with the channel. I put the mount dead center on top of the truss, but apparently that is not lined up with the cradle's center line, did not realize this when I built it. The axle is very well centered in the vehicle, so that's not my issue. I guess I'll cut the mount off the axle and put a new one in an inch over if everyone thinks it'll fix it, not a big deal.



But here's where I'm confused. Below are images showing a cad model of a bent arm in the cradle, at full stuff, with the end points of the control arm perfectly in line with the cradle and constrained to the same point in each picture. The movement of the joints allows the arm to come up at any angle and scrape the sides of the cradle even if everything is perfectly aligned. Is this somehow just not really a problem if the axle side is in alignment with the cradle center line?







Sorry sir. Dirtman just stirs the pot and seems to really not want to help out too much or so it seems.

The tunnel of the chassis and rear pinion are not perfectly centered under the vehicle. You have to make an arm that will allow clearance as the suspension cycles. If you used the back hole (mid arm length) the arm would have clearance and you could use a straight arm as we do. For our long arm setups we offer, we bend the arm down so it clears and we use 1.625 O.D. material. If you need a custom arm made, we are here to help. The arm being slightly off center 1" or so will not matter then at all.

In your rough 3D model make the mount in the chassis horizontal and you might see it a little better..

Hope that helps..

RK
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post #21 of 28 Old 05-26-2017, 09:00 AM
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LOL, facts. you guys make up more bs in your marketing to sell your junk to the uneducated consumer. I think you are just scared of people actually being educated on suspensions and components. Its easy to prey on and take money from the uneducated.

BTW I gave up on you guys long ago after installing one of your "mid" arm kit on a friends rig.

AS far as helping on the forums I guess RCO basically jumping on the guy for install because "There are no other explanations for what is going on here and it isn't a product fault."instead of actually reading the post to get the facts. Thats a lot of non help. and basically why I made the snarky remark.

I will keep on trying to educated fellow jeepers and you keep on trying to take their money.
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post #22 of 28 Old 05-26-2017, 09:09 AM
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Pick up one of these in the width you need and weld it to the frame end of the arm and it will keep the arm from turning. The axle side joint should take the bulk of the misalignment when flexing.
https://www.metalcloak.com/2-5-8-OD-...ing-p/7300.htm

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post #23 of 28 Old 05-26-2017, 11:21 AM
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I didn't "jump" anyone. I stated the very same thing that those before me eluded to and the OP even just said his setup is out of alignment, yet you're still trying to fix it with a self centering joint.

Good luck with the fix christensent.


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post #24 of 28 Old 05-26-2017, 11:23 AM
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You don't need to worry about any other joints or anything like that... Gravity is your friend in this case and will help keep the orientation of the bar down for the clearance you need, those joints will be tight enough to ensure the bar is not just flopping around on you.
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post #25 of 28 Old 05-26-2017, 01:13 PM
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Is it just rubbing the paint off and making a clean spot, or is it actually gouging the arm?

I still vote for bending the rearmost ears of that mount outward a bit. It will self center itself with the mount acting as a guide.

Kevin
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