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What's so wrong with radius arms?

anthrax323

anthrax323

NAXJA Forum User
Location
San Antonio, TX
I've been wanting to step up to long arms for ride quality reasons, and seem to be finding a lot of negative press on radius arms (but never any reason).

What's so wrong with radius arms? Up until recently I'd been eyeing the Rubicon Express LA crossmember and IronMan long arms, but if radius arms are really as bad as people make them out to be, I'll likely be more interested in the BDS 4-link long arm kit/upgrade.

Anyway, why does everyone hate radius arms?
 
I have almost 100k miles on my modified Ford radius arm setup. I love it, it wheels great and with a minor mod to convert the passenger side to wristed form, it flexes so much I definately need limiting straps. Cheap, strong, reliable, and works great. My answer would be that there is nothing wrong with radius arms.
 
Fore-most Cons:

Binding when articulating due to design.

Consistant Camber change while driving.

Single point (per side) of attachment and stress transfer to unibody/crossmember of axle.
 
ROBERTK said:
Fore-most Cons:

Binding when articulating due to design.

Consistant Camber change while driving.

Single point (per side) of attachment and stress transfer to unibody/crossmember of axle.
Click to expand...
Ford has run them on their trucks for years with no problems. Without wristing, I still get good articulation.
 
old_man said:
I have almost 100k miles on my modified Ford radius arm setup. I love it, it wheels great and with a minor mod to convert the passenger side to wristed form, it flexes so much I definately need limiting straps. Cheap, strong, reliable, and works great. My answer would be that there is nothing wrong with radius arms.
Click to expand...
I am working on some eb radius arms for my buddies Nissan Hardbody right now, do you have a pic or description of how you wristed the psngr side arm? Do they have a bend in them to make them parallel to the unibody rails? Thanks!
skullverradiusarms.jpg
 
Those are purdy. Mine are a lot simpler. I will see if I can get some pix tonight. I have been meaning to do a writeup for months but like keeps getting in the way.
 
old_man said:
Those are purdy. Mine are a lot simpler. I will see if I can get some pix tonight. I have been meaning to do a writeup for months but like keeps getting in the way.
Click to expand...

Thanks, appreciate it! I know what you mean, life sure has a way of doing that!
 
So I got to learn what "wristing" a radius arm is, and needless to say, it's not something I'm really too keen on doing (as my rig is 99.562% DD).

One thing that perplexes me, though... How in the hell do radius arms bind? It seems as though they'd be the least likely to bind of any suspension link setup I'm aware of. If someone could elaborate on what forces or movement limitations would result in binding, I'm all ears.
 
you should be more concerned about consistant caster change, since it can bring on death wobble if at all not addressed right to start, and even if addressed you are more prone to caster issues if you drive at all fast and careless. Since as the suspension droops (the body moves up) the Caster goes negitive...
 
Look at the arm that Skullver made. Look at the face of the mount where it attaches to the housing. As the suspension articulates - as one arm drops - that angle wants to change. Since the housing cannot twist, you get a bind.

Simple experiment - grab 2 broomsticks and hold one in each hand with them vertical. Now lock your wrists in place and rotate one arm up and the other down. See how the angles of the sticks change?
 
The longer the long arms are the better the castor should do, thats why short arms are so bad as you get higher the angle changes more as it drops the same distance.

Am I wrong there?
 
There are soooooo many threads debating the hell out of this.

If you are this worried about it, pick a setup that isn't radius arms. Rock Krawler, BDS, Poly Performance and Full Traction all make 3/4 link kits for the XJ. I've got the Poly 3 link and it's been great so far, on the street and the rocks.


ROBERTK said:
Consistant Camber change while driving.
Click to expand...

You mean caster, right? Camber doesn't change on a solid axle.
 
DoctorPhate said:
The longer the long arms are the better the castor should do, thats why short arms are so bad as you get higher the angle changes more as it drops the same distance.

Am I wrong there?
Click to expand...

You are correct. But who makes a short radius arm setup?
 
If you're just looking for a better ride for something that spends most of it's time on the road then radius arms will be fine.

Besides the inherit bind that's been talked about, the other big drawback to radius arm type suspensions is the high anti-dive they usually have. This tends to cause front end to lift up on steep climbs, but can be limited with a suckdown winch or center limit strap.

I really wouldn't worry about the caster changes or strength, they've been used on desert racers and stock vehicles for years and have done just fine at speed.
 
sunburned said:
You mean caster, right? Camber doesn't change on a solid axle.
Click to expand...

Yes, just saw that I put camber there and ment caster, as in my other post, sorry.
 
DieselSJ said:
You are correct. But who makes a short radius arm setup?
Click to expand...

Sorry now I'm getting confused, I was thinking control arms this whole time then I realized we were talking radius arms so I looked it up to refresh my piss poor memory and this is what I keep seeing..
0612or_03_z+1994_toyota_pickup+radius_arms.jpg


Is that not a control arm?
 
DoctorPhate said:
Sorry now I'm getting confused, I was thinking control arms this whole time then I realized we were talking radius arms so I looked it up to refresh my piss poor memory and this is what I keep seeing..
0612or_03_z+1994_toyota_pickup+radius_arms.jpg


Is that not a control arm?
Click to expand...

Control arm yes.

Radius arm design...
 
I just got back from a weekend trip that consisted of 325+ miles of 75+mph freeway driving and 30-ish miles of slickrock crawling on 7-8 rated trails, blasting up and down sandy washes and sand dune running and 325+ miles home. I drive my rig daily on the freeway (70+ mph) and have run TnTCustoms Y-link setup (radius arms) for nearly 3 years with no noticeable caster changes. I run an anti-rock swaybar setup which restricts droop to a point, but limiting droop is the only negative for my setup……whoop-de-doo.

The ride is nice, BTW.
 
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