• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Synergy Suspension 4 link Or Rock Krawler 3 link whats better?

Nick_n_ii

NAXJA Forum User
Location
Shelby, Ohio
Synergy Suspension 4 link Or Rock Krawler 3 link whats better?

Pros and Cons of each.

Not looking to do a the Synergy 3 link cause of welding to my D30. Replacing that with in a year or so.
 
Link to the synergy? I haven't herd of them. Never herd of people havin problems with the rock krawler.
 
More info? What kind of wheeling do you do? I run the 3 link from RK and love it. A 3 link has less bind than a 4 link. Some don't like having just the one upper and prefer the security of two uppers from the 4 link.
 
Trails, lots off off camber, long distance, tight woods, hills. And the XJ is a DD/weekend wheeler.

Right now I'm on 4.5" and 31's plan to stay that tall and go 33's or 35's down the road.
 
Sometime down the line I plan on going with the PolyPerformance 3 link. I especially like the thoroughness of the way the mounts are designed.
 
RK kits are pretty bulletproof. If you prefer a 3 link and it sounds like you do, go RK and be finished.
 
Go with a 4 link long arm bu Full Traction.
I would never look back and there is a sale right now on them.
Here is the flexing picture of this kit
http://www.virtualjeepclub.com/show...n-s-XJ-Flexing-Videos-and-Pictures&highlight=
video close to the bottem of the page

link to the sale price $2099
http://www.northridge4x4.com/proddetail.php?prod=PKG-FT-XJ-COMBO


CONS
Steel braided brake lines.
Shocks
Skid plate heavy duty
Large heims
great on and offroad performance
no harshness
running for almost 2 years.
Sway bar discos
bump stops
 
Did you check out my kit?
 
Did you check out my kit?

I would if I were you. I'm definitely going with his 4 link when I have the dough.

And he is a forum sponsor to boot!
 
Poly 3 link here. I picked the 3 over the 4 link because the stock upper bushings suck and I didn't want to deal with them anymore. The only welding you have to do is a single bracket in place of the stock passenger side upper. So if you switch axles in the future, all you have to do is replace that one bracket, which is probably $30.

Had the suspension kit on since August of last year and it's been great. Thousands of road miles with no issues and wheeling some hardcore trails. Brackets hang down, but they are beef so rocks won't hurt em. I'm on 35's so I don't really drag them much anyway. Technically there isn't much difference between this kit and the RK kit other than the frame brackets are way bigger and stronger.

I don't think I've found any cons with this setup. I just pulled off the short arms and threw on the 3-link and had no problems. Kept everything else on my setup the same.

Oh, the only thing I found was that it pushed my axle forward about 2", so my tie rod hit the passenger side sway bar link when I turned to the right. I took off the link and bent the sway bar mount as a quick fix, but recently put on a JKS sway bar mount extension and it solved the problem.
 
Did you check out my kit?

Yes I've looked at your kit. BUTT

I don't mean any disrespect but yours don't seem "beefy" enough to me with the small dia. links.

If the arms in your kit were 1.75 to 2" I'd be more likely to pick that kit over the other 2. I like your belly skid setup and all. Just not thrilled about a dinky link dia. I've bent 1.5" sold stock short arms in the past.
 
Last edited:
Forward axle push is something I am looking for.

Right now mine runs about a 1" back to far.

And I want to keep all my parts and just replace the short arms with long arm.
 
Dinky? Did you see the pictures of my accident and the damage it caused to everything but the links and heims? Not that Im bragging about the accident, that was my own unfortunate stupidity. lol You also have to remember that its 1-1/4 from flat to flat on hex material, 1.44 from point to point and I have never bent a link. I honestly dont see it very likely at all unless your running a 6,000LB buggy.

But thats fine, just so you know. I can customize my kit directly for your aplication. You would just have to pay the difference in steel. My kit will also push your front end an inch or more forward. ;)
 
Dinky? Did you see the pictures of my accident and the damage it caused to everything but the links and heims? Not that Im bragging about the accident, that was my own unfortunate stupidity. lol You also have to remember that its 1-1/4 from flat to flat on hex material, 1.44 from point to point and I have never bent a link. I honestly dont see it very likely at all unless your running a 6,000LB buggy.

But thats fine, just so you know. I can customize my kit directly for your aplication. You would just have to pay the difference in steel. My kit will also push your front end an inch or more forward. ;)
Well, see here's the issue you need numbers to back up claims.

When you do the math on your solid hex stock you'll see that the strength is actually way way less than that of even what most people use for steering linkage (1.5" OD x 0.250"wall tube).

Here is some math:
I'll spare you the details but the section modulus (S) of the following are (look up the formulas if you want to test these, I'm not typing them all out):

Hex through center on flats: 5999.4 in^3
Hex through center on corners: 6922.4 in^3
1.5" OD x 0.250"wall tube through center: 7839.2 in^3
1.75" OD x 0.375"wall tube through center: 13858.9 in^3
2" OD x 0.250"wall tube through center: 15828.9 in^3

Right away you can see how significant the difference is, but some real world numbers lets find the point load before the links would start to bend or fail. Obviously these numbers are just static and not impacts (like landing on a rock). We shall use a length of 30" for all of them.

We know that P (point load) = 4M (maximum bending moment) / L (length)
Where M = s·S
Where s = allowable bending stress) = .55 x yield strength
We shall use the yield strength for 1018 steel which is ~53700psi

Solving for those gets us the following point loads:

Hex through center on flats: 799.92 lbs
Hex through center on corners: 922.9 lbs
1.5" OD x 0.250"wall tube through center: 1045.2 lbs
1.75" OD x 0.375"wall tube through center: 1847.7 lbs
2" OD x 0.250"wall tube through center: 2110.5 lbs

Again, just the facts here. :)
 
Screw numbers.

My 2" x .25 DOM lowers, all 4, look like bananas.

My 1.5" x .25 tie rod looks like a banana.

But I guess the little hex stock will be OK, as long your link mounts are below the axle centerline. Mine aren't, which is probably a contributing factor.
 
While Bill's #'s are correct, Chris raises a really good point. A lot of the time people use lowers about the size of 2" OD 0.250 wall DOM or 2x2x0.250 box and they look like someone put them through a roller bender. People use those sizes because they're easy to come by and appropriate sized tube inserts for 1.25" joints fit well while maintaining good wall thickness in the threaded area. Those sizes seem to be a good comprimise between durablity and price. Having bent links is unacceptable by any means, but what do you think would happen to these little hex links when put through the same abuse? They're going to be fold in half.

I've also seen much larger joints wear out unreasonably fast in suspensions, so there's no way I'd ever trust that size.

It's hard to argue with results.
 
Last edited:
Forward axle push is something I am looking for.

Right now mine runs about a 1" back to far.

And I want to keep all my parts and just replace the short arms with long arm.


Like I said. Had mine on in an afternoon and the hardest part was removing the short arm kit because the bolts were seized in the RE joints and had to be cut out with a plasma torch.
 
Back
Top