another radius arm flip

[bigdfzj80]

Reasons for the flip:
1. Those brackets are a magnet to rocks! I do a little rock crawling and quickly discovered how annoying it it to always hitting the lower bracket on the rocks and inhibiting forward progress.

2. Free up some articulation. This mod has shown to free up some binding in the front. I will be adding some 14" to let the arms flex as much as they want.

3. A flatter arm is better for ride quality. I will be raising the panhard bar mount and modify shock mounts for taller better shocks, no more OME junk.

4. I got the tools so...why not?

I have the slee 4" lift. I'm going to be the test dummy and test the 4" minimum rule for the arm flip...here it goes...

 

[BlueCruiser84]

Cool project.

Why would it free up articulation? It's still two radius arms with four axle mounting points in front of and behind the axle centerline.

All the other points I agree with, wholeheartedly.

 

[ccslider]

Not to be a dick but ...you should get some better jack stands. Those blocks look sketchy.

Good luck on your project

 

[bigdfzj80]

Not to be a dick but ...you should get some better jack stands. Those blocks look sketchy.

Good luck on your project

ya my neighbor said the same thing. I jumped on the bumper and gave it a good side to side push. You cant see it in the picture but i have extra 35" tires on rims stacked underneath if the jacks were to fail.

 

[bigdfzj80]

Cool project.

Why would it free up articulation? It's still two radius arms with four axle mounting points in front of and behind the axle centerline.

All the other points I agree with, wholeheartedly.

Its hard to explain, but when the arms raised they are flatter therefore there is less forward and back movement when the axlemoved up and down. The same as a raised angled parnhard bar. Less forward and back movement frees up binding. Also, i will be spreading the mounts wider by about 1/4 inch to give the arms more room to flex inside the axle brackets

 

[ExpoMax]

Cool

Excited to see the results.

 

[nukegoat]

Its hard to explain, but when the arms raised they are flatter therefore there is less forward and back movement when the axlemoved up and down. The same as a raised angled parnhard bar. Less forward and back movement frees up binding. Also, i will be spreading the mounts wider by about 1/4 inch to give the arms more room to flex inside the axle brackets

Are the radius arms still going to be clamped on both sides by bracket? Are you just going to stack a washer in there?

 

[nukegoat]

Its hard to explain, but when the arms raised they are flatter therefore there is less forward and back movement when the axlemoved up and down. The same as a raised angled parnhard bar. Less forward and back movement frees up binding. Also, i will be spreading the mounts wider by about 1/4 inch to give the arms more room to flex inside the axle brackets

Are the radius arms still going to be clamped on both sides by bracket? Are you just going to stack a washer in there?

 

[Notch]

Its hard to explain, but when the arms raised they are flatter therefore there is less forward and back movement when the axlemoved up and down.

Assuming you're using the same frame mount location (instant center) and axle location, the axle will follow the exact same path it did before. No geometry change.

The "flatter" arm thing you read about is not talking about the actual arm shape relative to the ground. It's talking about moving the instant center to change the antidive characteristics of the suspension. This is where you could possible pick up better or different ride quality, especially under braking or accelerating.

Adding some flex and ground clearance is cool though.

 

[bigdfzj80]

well already ran into problems. the brackets cannot just be cut and flipped because the axle is not the same diameter on each side, which I already knew but its more different than expected. Also I cant reverse the bracket because the axle does not sit in the middle of the two attachment points. So i dont know how this mod can be done using the stock brackets. I may have to make my own brackets

 

[bigdfzj80]

Are the radius arms still going to be clamped on both sides by bracket? Are you just going to stack a washer in there?

cut them, widen them by 1/4 ", then two 1/8" washers on each side

 

[nukegoat]

Assuming you're using the same frame mount location (instant center) and axle location, the axle will follow the exact same path it did before. No geometry change.

Flat out wrong and nor is the instant center at the frame mount points. The relative position of the attachment points is a huge part of suspension geometry.

Edit: Except not wrong, because I am dumb

 

[BlueCruiser84]

Edit* Notch is right.


Seems to me you will have about the same articulation and ride characteristics as a stock LC with regards to the control arms.

Should drive really well with the flat(ter) control arms. And the added clearance under the axle will be a nice bonus.

If you are going to the trouble to cut/widen the stock brackets you will probably be better off just building new ones. Especially considering the prOblems you have already run into.

Keep up the progress!

 

[Notch]

Flat out wrong and nor is the instant center at the frame mount points. The relative position of the attachment points is a huge part of suspension geometry.

Um, how so? Define your version of instant center and educate us then. Is it not the geometric center that the suspension rotates around? This is the rear bushing on the 80 front suspension or a point floating in space if you have a 3 or 4 link where Both ends of the links are free to rotate.

My point was, if you dont change the frame mounting point the geometry doesnt change. A straight link and a bent link behave exactly the same (geometrically) if the pivots are the same distance apart.

 

[Notch]

"RADIUS ARM TYPE

One of the more typical link suspensions for a crawler or daily driver is the Radius Arm system that you would find on something like an 80-series Land Cruiser. This suspension uses two lower arms that attach from the frame down to the axle....

The IC is located by the placing of the lower links at the frame; therefore radius arm suspensions typically have very high AS numbers and are none adjustable."

From this article Suspension Encyclopedia/4Wheel Underground

For those that want to know more, these are all geometrically the same kind of suspension - radius arm, two link, truck arms and ladder bars. They all have a fixed instant center at the frame mount and they are all different shapes to suit the application (not unlike flipping an 80 front arm..cough)

 

[nukegoat]

Um, how so? Define your version of instant center and educate us then. Is it not the geometric center that the suspension rotates around? This is the rear bushing on the 80 front suspension or a point floating in space if you have a 3 or 4 link where Both ends of the links are free to rotate.

My point was, if you dont change the frame mounting point the geometry doesnt change. A straight link and a bent link behave exactly the same (geometrically) if the pivots are the same distance apart.

Hes not proposing making a bent link. He literally is changing where the links attach to the axle. You think the geometry will remain the same?

Edit: Except it will, because I am dumb

 

[nukegoat]

Um, how so? Define your version of instant center and educate us then. Is it not the geometric center that the suspension rotates around? This is the rear bushing on the 80 front suspension or a point floating in space if you have a 3 or 4 link where Both ends of the links are free to rotate.

My point was, if you dont change the frame mounting point the geometry doesnt change. A straight link and a bent link behave exactly the same (geometrically) if the pivots are the same distance apart.

Oh and youre right about instant center. Senior moment. I was confusing it with roll center, which does indeed change when you change the radius arm mount locations on the axle.

 

[Notch]

Its a hinge. You can change the shape of one leg (which is what hes doing) and it will pivot in the same spot.

 

[LINUS]

Its a hinge. You can change the shape of one leg (which is what hes doing) and it will pivot in the same spot.

I think you're oversimplifying what'll happen.

The return spot will be the same but through the suspension flex it won't be in the same spots as a stock setup, for better or worse.
-It's along the same lines as caster plates that rotate on the rearmost bolt in the axle, or the plates that rotate on the axle center.

I'd have to draw myself some pics to prove myself right, but gut is telling me it does change in stroke. But I can be wrong as I'm dumb enough I still have to draw pictures.

 

[cruzer971]

I liked reason #4 on the original post. "Why not?" But a quicker and more effective rock crawling upgrade for me was to delete the ARBb bumper. That thing seemed like more of a rock magnet than my control arms were!