Radius Arm Suspension

[MountNGoat]

Neat... but you won’t need the traction bar with the 63’s if you’re using the right 3/4 ton springs. Extra weight.

You should start with a sway bar in the front first instead of the rear. Why do you need quick connect fittings?

What shocks and valving are you starting with for the rear?

A lot of work to use radius arms when with the same amount of effort you could have a bind-free and caster-controllable 3-link.. whatever though. Looking forwards to how it performs.

We'll see how it drives before adding the front, but pretty sure I'll have one. I am typically loaded very heavy in the rear with gear and food for long trips, so it makes sense to control the rear sway. King shocks/bumpstops all around. Valving is being set up by the provider. I considered a 3 or four link setup but wanted to give this a try first since it is more straight forward. My 80's manage the Rubicon just fine with radius arms and I like their street manners. Changing out to a linked suspension is still an option. As for the traction bar, I disagree. The 3/4 ton 63's that I'm running sit nearly perfectly flat when the truck isn't loaded. between my turbo diesel, H55F first gear and Black Box second transfer case, a lot of torque can be delivered to those springs either on or off the trail. As is often done in Alaska rigs there will also be air bags in back to help keep it level as load is added. As for quick connect fittings, it's goes on and off the trail enough that having an easy disconnect of the sway bar is a good thing. I do the Rubicon a couple of times a year, and also longer 'overlanding' trips as well.

Converting a 60 front to radius arms seems like a great idea. I would probably look into Bronco radius arms though rather than 80 arms. Bronco arms seem to allow a ton of flex and their are a ton of aftermarket options.

Interesting thought. From what I understand about about radius arms I would think that longer arms would contribute the most to better flex - maybe the Bronco's are longer.

Interesting concept and awesome parts. Got any pics of how you packaged the coilovers?

The coilovers haven't arrived yet. The plan is to use the compact (shorter end caps) 12" units from King.

 

[cruisermatt]

We'll see how it drives before adding the front, but pretty sure I'll have one. I am typically loaded very heavy in the rear with gear and food for long trips, so it makes sense to control the rear sway. King shocks/bumpstops all around. Valving is being set up by the provider. I considered a 3 or four link setup but wanted to give this a try first since it is more straight forward. My 80's manage the Rubicon just fine with radius arms and I like their street manners. Changing out to a linked suspension is still an option. As for the traction bar, I disagree. The 3/4 ton 63's that I'm running sit nearly perfectly flat when the truck isn't loaded. between my turbo diesel, H55F first gear and Black Box second transfer case, a lot of torque can be delivered to those springs either on or off the trail. As is often done in Alaska rigs there will also be air bags in back to help keep it level as load is added. As for quick connect fittings, it's goes on and off the trail enough that having an easy disconnect of the sway bar is a good thing. I do the Rubicon a couple of times a year, and also longer 'overlanding' trips as well.



Interesting thought. From what I understand about about radius arms I would think that longer arms would contribute the most to better flex - maybe the Bronco's are longer.



The coilovers haven't arrived yet. The plan is to use the compact (shorter end caps) 12" units from King.

You shouldn’t need to add air bags to keep the truck level, that’s what the sway bar is for.

You’re going to created a very inverted driving experience with only a rear sway bar. Name one OEM vehicle that only has a rear sway bar, or has a larger rear sway bar then front. Front sway bars are later diameter for a reason.

@GLTHFJ60 runs 3/4 ton springs behind a powerful 4BT with an axle that weighs twice as much with no anti-wrap bar. And I’ve seen him hammer on it with no rear axle wrap whatsoever.

 

[MountNGoat]

You shouldn’t need to add air bags to keep the truck level, that’s what the sway bar is for.

You’re going to created a very inverted driving experience with only a rear sway bar. Name one OEM vehicle that only has a rear sway bar, or has a larger rear sway bar then front. Front sway bars are later diameter for a reason.

@GLTHFJ60 runs 3/4 ton springs behind a powerful 4BT with an axle that weighs twice as much with no sway bar. And I’ve seen him hammer on it with no rear axle wrap whatsoever.

Air bags are for supplemental load carrying and ride height adjustment, not for reducing sway. By keep it level I meant keeping the rear from sagging - I'm well aware that air bags are not used as sway bars. I've discussed the issue with the build team of front only, vs. front + rear, vs. rear only for the sway bar, and as I said above after a driving experience I will probably add a front as well. I am aware, for example, that 60's had only a front, whereas 62's had front and rear, and that a rear only is not normally used. Just taking it one step at a time.

 

[GLTHFJ60]

You really don't need an anti-wrap bar with the 3/4t chevy 63" springs, especially not with a 1HZ turbo. In fact, with one you'd wear out springs faster and reduce overall articulation.

 

[Cruiserdrew]

You really don't need an anti-wrap bar with the 3/4t chevy 63" springs, especially not with a 1HZ turbo. In fact, with one you'd wear out springs faster and reduce overall articulation.

True! Why will an anti-wrap bar cause the springs to wear out faster? Curious.

@MountNGoat I've looked for axle wrap with mine in low/low/low and it really doesn't wrap with the 3/4 ton chevy springs. I think that heavy overload leaf is what really prevents the wrap.

 

[GLTHFJ60]

True! Why will an anti-wrap bar cause the springs to wear out faster? Curious.

I haven't read up on it in a while (since I decided not to run one) but the jist of it is that the arc that the sway bar forces the axle to follow through the available suspension travel does not match the natural arc of the spring. This will cause the springs to s-shape faster, the more time the axle spends away from the equilibrium point, where both arcs match.

This post sums it up well, from a company that sells a "traction bar" that combats the problems of an anti-wrap (aka ladder) bar:

Anti-Wrap Traction Bar

 

[MountNGoat]

Lots of good opinions here, even if they don’t all agree.

I will take measurements of the 63 leafs, and all the geometry and compute the axle rotation (from spring wrap) vs applied torque to get a feel for how much movement occurs. And the torque that can be applied from either the gear box or braking may not be as large as the torque from running the tire into something big that doesn’t move. Not going to happen in the next two weeks but it will happen.

 

[FJ60Cam]

Back to the original question(s)...

I’ve enjoyed my 80 series radius arm setup up front. It’s flexier than the SUA heavy leaf springs it replaced, but less than a three link (which requires more vertical room/lift than I have/want).

When I ran the OME stock replacement springs, it had a really soft ride and gave a 2-3” lift. With the OME medium springs I have now, it handles more like a sports car, and is in the 4” lift range. The downside is it needs a touch more castor correction (I have the plates now).

If you get it centered just right, you can stuff 35s without having to trim anything. It’s also nice not having the front springs in the way when you approach rocks.

The coil bucket, frame brace, panhard, and steering box relocation are fairly straightforward, but 60s & 62s will need a different approach to the rear arm mount, since it lands right in the middle of the transmission crossmember mount on the late FJ60s. (pre-85 60s & 62s are different)

As long as you keep money and time out of the discussion, it is totally worth it

 

[Beams37]

Back to the original question(s)...

I’ve enjoyed my 80 series radius arm setup up front. It’s flexier than the SUA heavy leaf springs it replaced, but less than a three link (which requires more vertical room/lift than I have/want).

When I ran the OME stock replacement springs, it had a really soft ride and gave a 2-3” lift. With the OME medium springs I have now, it handles more like a sports car, and is in the 4” lift range. The downside is it needs a touch more castor correction (I have the plates now).

If you get it centered just right, you can stuff 35s without having to trim anything. It’s also nice not having the front springs in the way when you approach rocks.

The coil bucket, frame brace, panhard, and steering box relocation are fairly straightforward, but 60s & 62s will need a different approach to the rear arm mount, since it lands right in the middle of the transmission crossmember mount on the late FJ60s. (pre-85 60s & 62s are different)

As long as you keep money and time out of the discussion, it is totally worth it

View attachment 1673926

Hey Cam,

I would love to look at this sometime and go out for a test drive. I'm very interested in this project.

 

[MountNGoat]

Hey Cam,

I would love to look at this sometime and go out for a test drive. I'm very interested in this project.

Perhaps if you offer up some semblance of coffee making know-how as a sacrifice, you will be blessed with an opportunity to drive the beast. Cam-ron is a java phenom.

 

[FJ60Cam]

Hey Cam,

I would love to look at this sometime and go out for a test drive. I'm very interested in this project.

Sounds like a plan!

Perhaps if you offer up some semblance of coffee making know-how as a sacrifice, you will be blessed with an opportunity to drive the beast. Cam-ron is a java phenom.

I actually owe him a test drive, since he already let me drive his sweet Erod-converted 62.

 

[FJ60Cam]

I’ll add that if using the 80 series front axle & steering setup, the turning radius and low speed steering effort are greatly improved due to the better Ackerman geometry.

This translates to easier parking lot and trail maneuvering.

 

[Beams37]

I’ll add that if using the 80 series front axle & steering setup, the turning radius and low speed steering effort are greatly improved due to the better Ackerman geometry.

This translates to easier parking lot and trail maneuvering.

We really need to explore this. Maybe I can swing by this weekend.

 

[507TLC60s]

Where did you get the bumper?

 

[507TLC60s]

Back to the original question(s)...

I’ve enjoyed my 80 series radius arm setup up front. It’s flexier than the SUA heavy leaf springs it replaced, but less than a three link (which requires more vertical room/lift than I have/want).

When I ran the OME stock replacement springs, it had a really soft ride and gave a 2-3” lift. With the OME medium springs I have now, it handles more like a sports car, and is in the 4” lift range. The downside is it needs a touch more castor correction (I have the plates now).

If you get it centered just right, you can stuff 35s without having to trim anything. It’s also nice not having the front springs in the way when you approach rocks.

The coil bucket, frame brace, panhard, and steering box relocation are fairly straightforward, but 60s & 62s will need a different approach to the rear arm mount, since it lands right in the middle of the transmission crossmember mount on the late FJ60s. (pre-85 60s & 62s are different)

As long as you keep money and time out of the discussion, it is totally worth it

View attachment 1673926

Where did you get the front bumper for the 60s

 

[FJ60Cam]

Where did you get the front bumper for the 60s

It's a custom one-off we made a few years ago.