another radius arm flip

[-Spike-]

I think one thing that would change is stress on the bushings though correct? Because having the bushings/arm on the bottom gives the bushings better leverage to limit rotational forces because of being closer to the contact patch vs on top of the housing and further from the tire contact patch.

Yeah, that's one of those things I'm not sure about. The positions of the axle tube mounts are pretty close whether the arms are above or below the tube. I'd guess the relevant spec is the distance from the axle shaft center to the bushings, and the relative angle of the bushings to the direction of vehicle travel. It may or may not matter that the bushings are above the axle, and my gut says it wouldn't as long as the distances (and therefore the leverage) don't change, but the relative angle might affect flex or 'feel', could be positive or detrimental, I have no idea.

 

[-Spike-]

I’m happy with how my junk rambles on down the trail.

I'm with you on that one. Sure, improvements could be made, but at this point I've made all the easy ones, I'm at the point of diminishing returns. Much more work is required for relatively small improvements. It will always be a station wagon, not a buggy. There are better platforms to modify for buggy performance than the 80 series.

 

[baldilocks]

I'm with you on that one. Sure, improvements could be made, but at this point I've made all the easy ones, I'm at the point of diminishing returns. Much more work is required for relatively small improvements. It will always be a station wagon, not a buggy. There are better platforms to modify for buggy performance than the 80 series.

Exactly. It gets to the point where the vehicle in question is under the knife so much over a 5 - 10 year ownership that it was rarely, if ever wheeled. Ground clearance and lockers baby!

 

[baldilocks]

this will all be rendered moot once you start welding on a stock axle tube anyway.......im predicting a bent axle in the very near future. geometry and engineering needs to take a back seat to some basic metallurgy of 25year old already noodly Toyota housing and housing deflection as it relates to your soon to be twisting splines and exploding diff.

What of the many who have done 3 links and welded on trusses, diff armor, gussets, etc. ? Are they magic? Perhaps they are in danger of a catastrophic failure? Would you recommend regular inspections for cracks?

 

[bugsnbikes]

im just saying if you are to the point of welding on all those bandaids because you are going to be pushing 37s pretty hard....... it seems a lot easier to just bump up to a 9.5” and a beefier housing. At the end of the day it’s still an 8” with 27splines.

I think the o.p. Said he planned to beat on em......and I’m seeing close to 1.5” spacers which isn’t going to help the leverage on those axles which tend to bend near the balls.

The flip is cheap and it’s really only time vs $$$. so if they hold up for a while and give a touch better suspension characteristics....have at it.seems like a fun project.

I would however open up the mounting points 1/4” or so as its the mounts which limit twist. You will chew up the bushings a tad quicker but gain a bit of flex if that’s what your after.

 

[baldilocks]

You mean a 9.5 third and a custom housing? I’ll beat my Toyota parts until they show me they need to be replaced. I don’t think I any of us are racing, at least not for money.

 

[mudgudgeon]

Actually now I think about my statement, if the arm is flipped to the top of the axle, the wheelbase doesn't change right? The arm is in a different point in its arc, but the axle hasn't moved. Am I right?

With a flip, axle moves forward fractionally. It's insignificant.

I think one thing that would change is stress on the bushings though correct? Because having the bushings/arm on the bottom gives the bushings better leverage to limit rotational forces because of being closer to the contact patch vs on top of the housing and further from the tire contact patch.

I'm fairly certain there are other vehicles with radius arm suspension that have arms oriented above the axle (just can't think of an example)

 

[nukegoat]

@Notch @-Spike-

I'll eat crow on this one. I spent some time reading some SAE publications on the topic. You both are right (along with whoever else was saying the mounting points don't matter) as far as suspension kinematics are concerned. I'm going to leave my ornery comments in this thread but will edit them to reflect that I am an idiot

 

[Lumpskie]

What about this effect:

Where there is some gain is the bushings mounting the axle are closer to horizontal with the pivot point (frame side). So there is a little less forward and backward movement of one side relative to the other at the bushings (not at the axle), so there may be less bind in the bushings. Though I believe much of that bind has to do with the axle trying to be twisted like a swaybar as one side tries to make it move clockwise and the other side (during articulation anyway) tries to make it twist counter clockwise. How much bind is caused by each? I don't know, but the binding from twisting is what wristed arms alleviate, so I'm guessing that's the lion's share?

I don't know how much effect it has, but there has to be some effect, right?

 

[White Stripe]

Pretty good discussion here and not too much monkey poop thrown. Very informative and nice to hear all the different viewpoints.

 

[HDJdreams]

@Notch @-Spike-

I'll eat crow on this one. I spent some time reading some SAE publications on the topic. You both are right (along with whoever else was saying the mounting points don't matter) as far as suspension kinematics are concerned. I'm going to leave my ornery comments in this thread but will edit them to reflect that I am an idiot

Thanks for the clarification. I THOUGHT the shape of the radius arm and exactly where it attached to the axle didn’t matter, just location of the pivot point relative to the axle centerline. (Assuming stiff bushings with negligible deflection)

This thread got me wondering if there was 5th order kinematic voodoo I was unaware of.

 

[nukegoat]

Thanks for the clarification. I THOUGHT the shape of the radius arm and exactly where it attached to the axle didn’t matter, just location of the pivot point relative to the axle centerline. (Assuming stiff bushings with negligible deflection)

This thread got me wondering if there was 5th order kinematic voodoo I was unaware of.

Right. There's some voodoo with the length of the radius arms and distance between bushings and distance from bushing to axle centerline. That's how the superflex arms do anything beyond what the OE radius arms do. Flipping the radius arms on the 80 axle housing will load the bushings differently (not qualitatively better or worse - that's a judgment call for the user to make) since nobody is going to weld them back on with perfect radial symmetry.

But the roll center and other suspension characteristics don't really care as others pointed out far earlier in this thread

 

[SoCal FZJ80]

Wow, same radius arm flip discussion... just 10 years later. Just for reference, it’s a great mod to do if you have the resources to do it. I’ve done it two different ways, by completely cutting the brackets off, then copying the pattern of the original brackets onto new metal combined with the pattern of the top of the axle tubes. I’ve also made brackets that located off of the original bolt locations and went completely around the axle tube. (Pic Below). First option gets the 4” rise, second option allows you to adjust placement for different heights or forward or rearward depending on what your requirements are.

 

[-Spike-]

@Notch @-Spike-

I'll eat crow on this one. I spent some time reading some SAE publications on the topic. You both are right (along with whoever else was saying the mounting points don't matter) as far as suspension kinematics are concerned. I'm going to leave my ornery comments in this thread but will edit them to reflect that I am an idiot

Lol, you have my respect sir, glad you found some corroborating evidence. Many people wouldn't bother to say anything if they found out they had a misconception like that. They'd just slink off and leave the audience hanging, not knowing how the situation resolved.

Edit: That was worth the 5 minutes I just spent to check out your edits, funny s***.

 

[mudgudgeon]

Edit: It will behave the same because the links are connected to each other, and Notch is a better fabricator in addition to being a better engineer than myself, and has a much stronger, longer lasting head gasket than my own, which always blows too soon

Fixed that edit for you dude.

 

[mudgudgeon]

Lol, you have my respect sir, glad you found some corroborating evidence. Many people wouldn't bother to say anything if they found out they had a misconception like that. They'd just slink off and leave the audience hanging, not knowing how the situation resolved.

Edit: That was worth the 5 minutes I just spent to check out your edits, funny s***.

Agreed on all counts

 

[ExpoMax]

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...
View attachment 1645999 View attachment 1646000 View attachment 1646001

View attachment 1645989

View attachment 1645991

I applaud you for cutting those brackets off that well. I cut mine off last night, and they turned into like 12 pieces haha. I think I’d just have some new 1/4” brackets made that fit the control arms if I was in your position. Be a bit stronger than the factory 3/16” stuff.

 

[bigdfzj80]

THis is a slow project, Im slowly picking away at it. There is no way to use the stock bracket for reasons I stated above. I took my 4" caster correction plates and made some brackets from them. So what i did is cut the bracket in half and made sure the front of the arm bolts in perfectly and weld it to the axle. then I will set the caster in just right and weld another set of brackets for behind the axle mount. So there will be 4 separate brackets instead on 2. This was easier because of the asymmetrical and weird shape of the housing. Plus im moving the axle forward a little bit.
the last photo shows how i spread the bracket to give more movement of the arm inside the bracket

 

[bigdfzj80]

another reason why flipped the arms is because i got a thick heavy duty tie rod and the caster plates tilted the back of the axle down so the tie rod rubbed on the radius arm and made a grinding sound when i would try to turn when the suspension was flexed. There was definitely a clearance issue there.

 

[baldilocks]

@bigdfzj80 - How did this project turn out.? Pics tell the story best.