LongArms... Radius style vs 3-4-5 link

Caver Dave

Caver Dave

Just holdin' it down here in BFV
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Would like to know the real differences regarding "radius arms" ("Y" tubular type like IronMan/IRO/RE/etc) vs the others. I've read that radius arms will bind due design, but have also read that some (specifically a reply from Rusty's) will not because of joint selection?

I'm leaning towards the radius style over a true 3/4/5 link due to packaging/simplicity. However, if they leave *that much* on the table, would consider the alternatives (as a zillion of them have been sold, I have a hard time believing they don't function pretty good)...

Could someone explain this "binding" & the claims by Rusty that theirs do not? I'm a picture guy and having a hard time following the descriptions...

:beer:
 
Call Andy at Iromman I'm sure he can set you up well
 
Picture your axle as just a piece of tube. Now picture two pieces of tube welded to that tube (axle). Now picture the ends of those two tubes attached to your frame with joints. It will only travel up and down like a swingarm. It won't allow one end of the tube (axle) to go up while the other goes down. The welds would have to rip in order for that to happen. That is a radius arm setup. The bushings that connect the tubes to the axle deform to allow the axle to 'flex' (one end up, other end down).

A 3 or 4 link is a much preferred setup.
 
drkelly said:
The welds would have to rip in order for that to happen. That is a radius arm setup. The bushings that connect the tubes to the axle deform to allow the axle to 'flex' (one end up, other end down).
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No, not quite. You're thinking of a stock-ish 66-79 Ford front end with rubber radius arm bushings. The Y-link style arms that he's talking about will have more flex due to the additional bushings and the pivot at the mid-arm. How much depends on the geometry and the bushing design, but I've seen y-link setups with stupid amounts of travel.
 
shawn said:
No, not quite. You're thinking of a stock-ish 66-79 Ford front end with rubber radius arm bushings. The Y-link style arms that he's talking about will have more flex due to the additional bushings and the pivot at the mid-arm.
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That's my understanding, the Ford radius arms will bind pretty good. But, the Y-links aren't as bad for those reasons.

shawn said:
How much depends on the geometry and the bushing design, but I've seen y-link setups with stupid amounts of travel.
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Exactly! I've seen some longarmed TJ's & XJ's that had ridiculous flex (ramp champs) and worked just as well on trail...

For those in the know, what's the best (your favorite) combo to accomplish this?
IOW, what are the pros/cons for each joint type (OE\urethane bushings/various cartridge joints/heims) in each location (axle lower/axle upper/mid-to-lower/frame) for a 98% offroad only application? Others have said that some joints are pure crap and require rebuilding after every ride, while others (like RS heims and certain cartridge joints) are generally good for years...
 
i would suggest a heim/cartridge joint at the frame & mid-to-lower mounts. You could also run one at the upper axle mount. I would run a bushing at the lower axle mount to prevent twist in the lower arm. Heims on the upper allow you to adjust caster & pinion angle.

also, I am guessing this is for the front not rear?
 
if you have adjustable joints at all locations, there is enough misalignment in the heims to allow it to "flop" around... not a big deal, just annoying. running a bushing somewhere will help prevent this.

on the flip side, the more threaded joints you have (bushings or heims), the more adjustment you will have in your suspension.
 
Caver Dave said:
That's my understanding, the Ford radius arms will bind pretty good. But, the Y-links aren't as bad for those reasons....
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It all depends on what bushings and joints are used on both designs.

I took the easy/cheap way out when building my cab truck, and used Ford late 70's radius arms. I would take the extra time now to do a true 3-link front with panhard rod. That is what I plan to change my cab truck to one day when I get time. A properly setup 3-link/panhard suspension system will outperform a radius arm setup.
 
paradisePWoffrd said:
if you have adjustable joints at all locations, there is enough misalignment in the heims to allow it to "flop" around... not a big deal, just annoying. running a bushing somewhere will help prevent this.
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Gotcha! ;)
paradisePWoffrd said:
flip side, the more threaded joints you have (bushings or heims), the more adjustment you will have in your suspension.
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Outside of adjusting caster when changing lift heights, how much more is needed/beneficial?
 
drkelly said:
It all depends on what bushings and joints are used on both designs.

I took the easy/cheap way out when building my cab truck, and used Ford late 70's radius arms. I would take the extra time now to do a true 3-link front with panhard rod. That is what I plan to change my cab truck to one day when I get time. A properly setup 3-link/panhard suspension system will outperform a radius arm setup.
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This is also how I feel. A well setup 3 link is stonger and your joints will last longer too. Packaging a 3 link is pretty easy to do, just remember to take into account that you will need a panhard bar that runs parallel with the drag link and has to clear the upper link if you rin it on the pass side. This is sometimes the hardest part to figure out.

I personally don't care for radus arm setups. they have become pretty popular in the aftermarket nowadays because of cherokees. It allows you to bolt on a crossmember that has 2 link mounts made into it and not have to modify the exhaust or axle brackets. They flex really well with the right joints, but do bind. One of the bronco companies made a thing you weld into an axle tube that allows it to twist. It completely eliminates the binding issues but seems a little excessive when you could just do a three link and not worry about it.

Make a peace sign with both hands. Make your pointer and middle finger look like the upper and lower links of a Y-type radius arm in front of you on each hand. Pivoting at your wrist lower one hand and raise the upper as if your finger tips were connected to the axle tube. You'll notice that the axle tube would have to twist in order for this to work. Everytime this happens you're forcing the bushings to give. That IMO wears them out a lot faster than they should wear.

If you do end up doing a radius arm setup I'd do poly at all the points where the links mount to the axle and a johnny joint at the frame. Then a heim or JJ where the upper meets lower so you can adj. caster. Call Andy from IronMan he has bushing he uses that work great for this setup. He's put in the time and research to find one that holds up for a long time.
 
Fact: All radius arms create bind. There is no way around it. The amount of bind and how it affects your mounts depends on the joints themselves. In most cases travel is limited by well.... common sense. This does not always happen. When you have taller lifts, large amounts of wheel travel and coil ejecting droop, bind becomes very real very fast. The true benefits of a good radius arm setup are the minimal amounts of caster change throughout the cycle of the suspension. I will tell you right now I have had customers that put the longest shocks they could on their jeeps, did not run limit straps and went for the super flex cool kid pictures and ripped the LCA mounts off of their Dana 30's. At this point the flex is not doing any good on the trail. The amount of flex becomes counter productive and even dangerous to the point of helping the vehicle tip over.

We use a 95 durometer poly graphite bushing at the axle end with a threaded stud direct tapped into 2.0x.281 Dom with 6" of thread at the axle. This allows light deformation of the poly to allow for bind without splitting the poly. We then direct tap 9 inches into the other end of the tube and run 8-9" of a 1.5 CRS stud double welded to a Currie johnny joint for the frame. This allows for the builder to rotate the arm to the ideal angle for the upper arm to mount.

We then use 88 durometer on the upper arms that have the same specs as our standard uppers but with a 1/2" 12 pt. grade 9 through bolt. There is tremendous stress on this joint. anything less is well.... less.

The point of the poly on all points axle side is to allow some give when the arms bind. If you properly limit your up and down travel, set your caster to the correct angles and use some common sense with your setup a radius arm will out perform a 3 or 4 link on the road to and from the trail. It will also work very well on the trail and last for years. The 3 and 4 link will have more caster change in most cases on factory vehicles because there just is not enough room for the right lengths to eliminate that.

If a 3 link fails you lose everything up front.

In my humble opinion a proper radius arm is going to be the best driving setup as well as most reliable on the street and trail.

If the vehicle is trail only. Do a four link with a pan hard or just a triangulated 4 link. while 3 links create no bind, any failure is catastrophic and usually involve replacing everything frame down in a front end.

Andy Carter
7047963502
www.ironman4x4fab.com
 
I have owned and driven both styles. I will say and admit that i dont know why one is better than the other. I will say my 3 link set up on tj outperforms the long arm radius arm setup i had in the past by leaps and bounds. It drives better on the road and on the trail.
 
IronManAndy said:
I totally agree, It just puts a whole crap load of force one 2 singular points. The design works great but the assembly must be taken very seriously and have no weak points.
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Just like on a radius arm setup......since there are only 2 joints taking the majority of the load in that setup and it offers as much, if not more potential damage if one of those joints lets loose.........

Radius arm setups work well for those applications where a properly set up 3 link/panhard design seems not doable. In a radius arm setup the pinion angle does not change through the suspension cycle but the castor/steering does. Radius arm setups offer some less desirable suspension characteristics to their properly setup counterparts. However, they are much easier to design/ install........
 
OK, yet another question... Do either/both of these require (will likely want) the use of a "sway-bar" (like Currie's Anti-Rock)?
IIRC, most of the 3/4-link folks use something to keep the suspension from doing a total list to the downhill side, where I don't recall seeing that on the RA-style links... maybe the "binding" inherent to RA links negates it more?
I guess where I'm going is that packaging longarms/coils/shocks/trackbar will be hard enough... without having to add upfront/go back after the fact to add a swaybar...
 
if you are running coil springs and shocks up front, you will not likely need a swaybar with radius arms or 3 link if it is offroad only. sway bars are nice when driving on the road or at speed though, with any of the suspension designs.
 
Packaging a antirock style swaybar can be challenging but you should be able to do it if needed. You may not need one depending on the coil that you end up using but I would try and plan for it just to be safe so you can put one on in the event you feel you need it to balance the front coils/rear leaf suspension setup.
 
paradisePWoffrd said:
if you are running coil springs and shocks up front, you will not likely need a swaybar with radius arms or 3 link if it is offroad only.
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Are you running an antirock (or similar) on the Bronc?

zubz said:
You may not need one depending on the coil that you end up using but I would try and plan for it just to be safe so you can put one on in the event you feel you need it to balance the front coils/rear leaf suspension setup.
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Guessing that tall(5"-10" lift)/softer coils might require one, where say a shorter(OE-4")/stiffer coils might be able to overcome the unloading on sidehills/angles?

The only time I've ever noticed it was on a buds 4-linked (and un-"swayed") LWB Jeep... 5* past perfectly flat, the uphill side completed unloaded/the downhill compressed and the whole rearend listed like it was gonna flip! He added a DIY "antirock" type setup that totally cured it...
 
Caver Dave said:
Are you running an antirock (or similar) on the Bronc?



Guessing that tall(5"-10" lift)/softer coils might require one, where say a shorter(OE-4")/stiffer coils might be able to overcome the unloading on sidehills/angles?

The only time I've ever noticed it was on a buds 4-linked (and un-"swayed") LWB Jeep... 5* past perfectly flat, the uphill side completed unloaded/the downhill compressed and the whole rearend listed like it was gonna flip! He added a DIY "antirock" type setup that totally cured it...
Click to expand...

On my buggy, I am not running one with air shocks. the bronco didnt need them with coils up front but did with air shocks

I have been in rigs with air shocks & coilovers that needed them. I have also driven a few taller jeeps that needed them on the road but not off.

I would say your logic might be close. Suspension design does come in to play some, but "feel," "comfort", and shocks play a big part deciding if you need a swaybar.

as said, they are typically not that difficult to package in afterwards if needed
 
zubz said:
Radius arm setups offer some less desirable suspension characteristics to their properly setup counterparts. However, they are much easier to design/ install........
Click to expand...

I've seen a few XJ's with those radius arm setups display some weird axle hopping motion when the rig is spinning the tires trying to climb an obstacle.
 
I have radius arms. When I first built them I didn't know what I was doing and both broke on the trail. That was in 07. My axle rolled up and made a mess as a spring popped out. I got it home and then fixed my weak point. I then found because of my design I had ALOT of binding. So I wristed the passenger side. It flexes pretty awesome now and the only thing stopping my droop is shocks. I love my setup and I know it works great. I am building a long arm Y link set up now for a friend. We will over build it big time so we have no points of failure.
 
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