Radius arm questions

[zukijames]

Just cycled maddies suspension.. It's mocked up with 52 inch lowers and single radius arm on passenger side( like Jeff Stevens suspension but longer links.

We lifted the pass tire up and the diff rotated down.. Alot .

In a radius arm set up does the length of the upper part( the one that mounts on top of lower link and axle)
Have anything to do with pinion dive?

I figured it didnt seeing how factory radius arms are just one piece .


Sorry I suck at explaining I'll go take a pic.

Ps it might be the duct tape streching or have something to do with only having a radius arm on one side.

We plan to add one to the other side but it will be easily removeable for added flex .. Kinda like a wristed radius arm

 

[drtsqrl]

James, the length of the upper arm won't matter, the pinion angle is fixed regarless of the upper arm length. The pinion angle change will be less with a longer lower arm than a short arm with the same shock travel, but at 52" your arms are already super long. My set-up works fine for me, but my front shocks are only 12" travel. Make sure you have enough u-joint angularity at the t-case. A double carden driveshaft would be best. I'm using a single u-joint at the t-case end (one of Tom Woods offset joints), but at anything over about 25 mph with the front hubs in the driveshaft vibration is pretty bad.

 

[zukijames]

dont worry i will put more tape on and sleve the link with another piece of pvc before we take it to the trail.

panhard didnt end up as flat as i wanted but its not bad

 

[zukijames]

Thanks Jeff that's what I thought about it being fixed . And she has a Double cardigan already but i don't know if it will work going to the Dana 60 . Do you think a radius arm on the other side Would help the vibes and stability at high speed?
We are going to try to come down the first week of June.. Let's do Prichett .. Hopefully ya won't have to tow me out

 

[DaveB]

Radius arms do twist the pinion a lot. If you have space remove the radius upper arm and (edited for RockMonkey) add an independent upper arm and it will work better for pinion tip. Also radius arms put twist on the axle when one side is up and the other is down that the links or the axle tubes have to account for.

 

[RockMonkey]

Radius arms do twist the pinion a lot. If you have space add an independent upper arm and it will work better for pinion tip. Also radius arms put twist on the axle when one side is up and the other is down that the links or the axle tubes have to account for.

I must be reading this wrong, because it sounds like you are recommending an upper control arm in addition to radius arms, which is a terrible idea! They would fight each other to move the axle in different arcs, causing binding and breakage. Don't do this!

Radius arms move the pinion in a very predictable arc. If you put the radius arm joints the same distance from the axle as the drive shaft joint, the pinion will always point at the joint.

Triangulating the radius arms will drastically reduce the twisting force placed on the axle during articulation.

 

[zukijames]

Thanks Dave the reason we are running them is because I've read they can have a sway bar effect and her rig is pretty tall and running air shocks front and rear.

So we are hoping the radius arms help keep it decent at speeds..

When shes goin to be running boulders and twisty stuff we will only run a radius arm on one side allowing the whole axle to twist.


Hope that makes since I'm not good with words.. There really is no room .
It's a v8 so dual exaust manifolds.. The t case is clocked and almost flat belly from factory!

So right where the upper link/links should be .. There is exaust ,driveline or t case.


The frame rails inside to inside are 2 inches narrower than my samurai!


Thanks for your help guys .. I know I've been a pecker head on Here a time or two so it's awesome guys will still take time to
Post on my stuff.


One more question. I always thought with a pan hard lowers hadn't be completely strait as In no triangulation..
But buck(raced a yellow landrover in koh 2 years ) said triangulating the lowers a little, bushings on one end of links and panhard, and panhard being slightly negative ( axle mount higher than frame)

Was the best way to set up with a panhard for speed

How much triangulation is too much on the lowers?

 

[zukijames]

Thanks rock monkey! Your the suspension man!

 

[DaveB]

I must be reading this wrong, because it sounds like you are recommending an upper control arm in addition to radius arms, which is a terrible idea! They would fight each other to move the axle in different arcs, causing binding and breakage. Don't do this!

Radius arms move the pinion in a very predictable arc. If you put the radius arm joints the same distance from the axle as the drive shaft joint, the pinion will always point at the joint.

Triangulating the radius arms will drastically reduce the twisting force placed on the axle during articulation.

No way was I suggesting that they add another upper arm in addition to the radius arms but I can see how my wording wasn't clear, I was suggesting that they go with a 3 or 4 link with pan hard bar and NOT do the radius arms.

 

[RockMonkey]

No way was I suggesting that they add another upper arm in addition to the radius arms but I can see how my wording wasn't clear, I was suggesting that they go with a 3 or 4 link with pan hard bar and NOT do the radius arms.

I hoped that's what you meant. I didn't want anyone reading this thread to add any control arms to their radius arm suspensions.

 

[zukijames]

wait so i need to go take the two upper links off of my radius arm set up? dangit guys !

do radius arms really help with body roll .. if not i will add an upper link on the outside of my frame.. but then she wont be able to turn completly lock to lock

 

[I Lean]

Two parallel-ish radius arms do try to twist the axlehousing under articulation, which is where the "sway bar" effect comes from. The more you triangulate those radius arms, the less restriction to articulation you get.

With joints at both axle points like you have mocked up, you probably won't want to use a second radius arm. There won't be much "give" at all, and something will wear out or break fairly quickly. (most likely races in the flex joints, but it could be something else also...like the axle housing)

If you're going to do two radius arms, I like rubber bushings at all the axle connections. That allows for some squish and makes it work out pretty well.

If you do just the one radius arm, your pinion angle will remain constant in relation to that one radius arm--and 52" long, you won't get much caster change really. Then you can add a separate swaybar if you need one.

 

[Herzog]

If you're going to do two radius arms, I like rubber bushings at all the axle connections. That allows for some squish and makes it work out pretty well.

Came to say this. Use rubber bushings at all ends except for the frame side lowers if you do double radius arms. Don't bother with poly, they will wear out super fast. Look into clevite bushings.

Your mockup with the tape is probably deceiving you because with a radius arm the pinion should stay in a static position because the entire housing rotates with the arc of the arms.

 

[zukijames]

thanks guys i should have known to put bushings . my old set up had joints at the frame. bushings on the rest..

my buddy had a setup on his xj . replaced bushings with joints.. the breakage started !