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Looking over Clayton's LA kit on another part of the forum. Looks interesting but I remember there's some criticism of radius arm front suspension designs like this, RE's, etc. Can anyone explain the issues?
 

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Looking over Clayton's LA kit on another part of the forum. Looks interesting but I remember there's some criticism of radius arm front suspension designs like this, RE's, etc. Can anyone explain the issues?
It's just a poor design. There is inherent binding anytime the axle articulates, so the bushings tend to wear out pretty quickly.
Some people that run radius arms will leave the jam nut loose on the upper radius arm. This allows the system to "twist" a little, BUT creates a clunk and can mess up the threads.

Ford used to put a a 2-piece rotating axle tube on the long side that allowed the entire axle to twist, putting less stress on the radius arm bushings.
But that must not have worked that well because most people have never even seen or heard of that axle...;)
 

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My experience with radius arm suspension is with hotrods. The old I-beam axles are made to flex which is something a differential won't do. I have seen hotrods with tube axles break kingpins, rod-ends and heims as well as bend frames. It just doesn't seem like a good design for offroad use.
 

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It has inherent binding. If you run a disconnect on one of the upper control arm (antirotation) you can get some mad flex. Like stated above you can also mod the axle to flex/rotate; BCbroncos makes the kit.

If you do go with it you need to stay away from any joint that uses Poly or rubber at the frame location. Ford got away with it by using a bayonet style joint at the frame. The flex comes from the frame locations ability to rotate, all the other joints don't move much if you don't have binding at the frame.

They are a bit more stable on the road due to its swaybar nature. My old Bronco never had bad body roll and I never had a swaybar.



Sent from my little magic box.
 

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Iron Rock Off Road has a radius arm kit for the xj and zj that removes the radius arm on the pass side. That would get rid of the bind issues.
Here is a link to one of there kits.
http://www.ironrockoffroad.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=IROR&Product_Code=IR-X8CPK&Category_Code=PFX
Think this is a bad Idea to do this to a JK?

I'm working on the 3 link in the rear right now. And it's close to being done. Got my homemade brackets welded on this morning. Next I was planing on doing the radius arms up front. Mainly because it would be easier for me not to make the upper mounts for the long arms. And cut the exhaust.

I have looked at many pics online at the RE long arm kits on the JK and they seem to flex pretty darn good. I don't mind changing two bushings ever now again if I had too. Then again why not add flex joints on all ends. Why do they not do that? Cause of drivetrain vibes. Someone please school me on this.
 

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yeah stay away.... the the radius arm doenst work at all.....




On a JK you dont have enough room to get the front end to bind... I run Raduis arms and have zeros issues with flex/travel. The Bushing issue that was mentiones is in the rear for the RE kit so that isnt even a valid arugement. Also if you fell like the upper bushing on the axle side is binding they make a Jhonny joint replacement kit so that joint will flex as well. Its awesome to see guys toss shit out that have no experiance with this particular application...
 

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yeah stay away.... the the radius arm doenst work at all.....


On a JK you dont have enough room to get the front end to bind... I run Raduis arms and have zeros issues with flex/travel. The Bushing issue that was mentiones is in the rear for the RE kit so that isnt even a valid arugement. Also if you fell like the upper bushing on the axle side is binding they make a Jhonny joint replacement kit so that joint will flex as well. Its awesome to see guys toss shit out that have no experiance with this particular application...
My only experience is helping put three sets of bushings in an RE front radius arm kit within six months, same JKU owner had the same problem with his TJ's Nth degree kit. Another TJ on 42s with one-tons a friend of mine bought with an RE radius kit, same thing. They all flexed well, but the two TJs and a JKU I delt with did not seem to hold up well. All were front axle bushings.
 

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ok, stupid question, what exactly is control arm binding? Is it the point where the joint can no longer articulate? Or do I have that wrong?
 

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ok, stupid question, what exactly is control arm binding? Is it the point where the joint can no longer articulate? Or do I have that wrong?
You have right. The radius arm itself is designed to be a ridged assy.
Little motion at the axle and all the motion at the frame. If designed wrong when your frame side it at max, what is left are the bushings at the axle.

The other binding issue is due to the two control arms being ridged, as one side drops and the other stays, the only way for it to deal with the mismatch is to twist the housing.

I've had some mad flex on my Bronco, with now issues. The other plus is it has a bit more stability, by acting like a swaybar.


Sent from my little magic box.
 

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ok, stupid question, what exactly is control arm binding? Is it the point where the joint can no longer articulate? Or do I have that wrong?
What I have seen is the upper axle mount front control arm bushing go. Basically the bolt would completely max out within the mount. If you call how a bolt goes through a normal control arm mount 0 degrees, along an X-axis, the bolt under "bind" would pretty much be at a 45* angle. The bushing is what would have to take that and eventually fail.
 

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Iron Rock Off Road has a radius arm kit for the xj and zj that removes the radius arm on the pass side. That would get rid of the bind issues.
Here is a link to one of there kits.
http://www.ironrockoffroad.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=IROR&Product_Code=IR-X8CPK&Category_Code=PFX
Think this is a bad Idea to do this to a JK?

I'm working on the 3 link in the rear right now. And it's close to being done. Got my homemade brackets welded on this morning. Next I was planing on doing the radius arms up front. Mainly because it would be easier for me not to make the upper mounts for the long arms. And cut the exhaust.

I have looked at many pics online at the RE long arm kits on the JK and they seem to flex pretty darn good. I don't mind changing two bushings ever now again if I had too. Then again why not add flex joints on all ends. Why do they not do that? Cause of drivetrain vibes. Someone please school me on this.
FWIW, I ran the Iron Rock Radius LA kit on both my WJ and my XJ. My XJ flexed like hell with that kit and rode great. It had johnny joints at the frame side. It was very easy to adjust the caster and I never noticed any binding. There is no upper link on the passenger side with this kit.

Here's my XJ with the 5.5" kit on the RTI ramp at Gulches:
 

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Besides binding (that you can work with sometimes) and bushing eating due to torque load (that you can sometimes fix with a big ass bushing) you have one thing that you can not and that is a pinion/caster angle that changes through the entire suspension arc.
this can be a severe problem with a short radius arm and can still be a problem with a long one even though this lessens the change and is something to keep in mind should either caster or pinion angle change be a problem with your setup.

Also a radius arm is not realy tunable and you are stuck with the numbers you got.

They "work" but I do not care for them. You also better have a beefy frame mount and radius arm as all the rotational torque is transfered directly through them.
 

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On the JK you will run into coil bind or shock bind unless your running a 10 inch lift before the arms bind. The companys that make a JK RA kits all offer a 1/4 replacement tranny crossmember where the arms mount. Ill agree with doc dialing them in is a bit more difficult but its is not impossible.
 
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