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Ford Radius arm vs 4 link - using the factory SD brackets on the axle.

Grendel

Iron Sharpens Iron
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May 19, 2020
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Is there any benefit to going 4 link over radius arms, using factory brackets on the axle?

This will be a street driven truck that needs to be on 38's to get into my back yard in the winter.

So, not big articulation.

What I have
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What I could do:
IMG_7622-2_543258a1-9c14-4ee3-b87d-cdc96b3afcfb_900x.jpg

Either would have a pan hard bar. Both would be arms outside the frame rails.

I am not into cutting off all the brackets on the SD60, just not enough value.
 
Better anti dive characteristics with the 4 link over the radius arms. That's the primary difference between 3/4 links and radius arms, AS/AD decreases which is an overall benefit. I'd say go for the 4 link
 
I don't know about only street driven, but off road I always ripped that tab off that welds to the "lower link".
 
Better anti dive characteristics with the 4 link over the radius arms. That's the primary difference between 3/4 links and radius arms, AS/AD decreases which is an overall benefit. I'd say go for the 4 link

I'd agree with this.

Not really what you asked but I have put 05+ axles into a few older trucks on budget swaps. I make a piece to laminate the stock ford arm. You can see where I put a slot in the bottom hole to rotate the axle a bit and gain some caster during mock up, then I welded it up once I got the placement where I wanted.

Obviously to get the arm to sit flat and keep stock super duty like geometry you need a big drop bracket on the frame side depending on the truck and lift. This F-150 was a road cruiser that may see some muddy paths. Not a rock crawler clearly

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I'd agree with this.

Not really what you asked but I have put 05+ axles into a few older trucks on budget swaps. I make a piece to laminate the stock ford arm. You can see where I put a slot in the bottom hole to rotate the axle a bit and gain some caster during mock up, then I welded it up once I got the placement where I wanted.

Obviously to get the arm to sit flat and keep stock super duty like geometry you need a big drop bracket on the frame side depending on the truck and lift. This F-150 was a road cruiser that may see some muddy paths. Not a rock crawler clearly

Nice work. Yeah, this isn't a wheeler. You can see in the pics, that I have adjustable arms by WFO... also did a dropped bracket.
 
in.

but for ford radius arm vs 3 link with panhard


i already hacked off all the stock ford mounts :homer:
 
Nice work. Yeah, this isn't a wheeler. You can see in the pics, that I have adjustable arms by WFO... also did a dropped bracket.

Gotcha, I didn't realize the top picture was your truck I thought you were just considering the options
 
in.

but for ford radius arm vs 3 link with panhard


i already hacked off all the stock ford mounts :homer:

I know that's an option for this, too... but I can't get my head around having that one link on that one side being safe with a 13,500lb truck towing another 20K lbs possible.
 
I know that's an option for this, too... but I can't get my head around having that one link on that one side being safe with a 13,500lb truck towing another 20K lbs possible.

oh ya for road and towing ford radius arm is tried and true, im surprised youre looking at a 4 link setup

im in for the difference in offroad performance, my next project is an 02 f350 for medium crawling, medium desert, medium road use, the typical do all that cant do anything :laughing:
 
oh ya for road and towing ford radius arm is tried and true, im surprised youre looking at a 4 link setup

im in for the difference in offroad performance, my next project is an 02 f350 for medium crawling, medium desert, medium road use, the typical do all that cant do anything :laughing:

Eh, I have a tendency to over complicate things at times.
 
you should plug it into a calculator, the 4 link might (will probably) have better roll steer characteristics which can be a pretty big deal on the street.
 
I've been wondering the same thing about running parallel links vs radius arms and ran across this: https://www.wfoconcepts.com/pr/DMAX-2001-2010-05+-Ford-Super-Duty-4-Link-Kit/9105/10446/18801/18754

Where it says "We recommend the 4 link setup for anyone running 8” or more of lift. We recommend the Radius Arm setup for anyone running less than 8” of lift." but I don't really understand the why especially on something that will probably be street-driven I would think sticking to radius arms is the easiest/most-predictable-outcome. I guess if you're running 8" inches of lift the angles would be too steep for radius arms and you'd have to run a drop bracket on the frame side?
 
I've been wondering the same thing about running parallel links vs radius arms and ran across this: https://www.wfoconcepts.com/pr/DMAX-...46/18801/18754

Where it says "We recommend the 4 link setup for anyone running 8” or more of lift. We recommend the Radius Arm setup for anyone running less than 8” of lift." but I don't really understand the why especially on something that will probably be street-driven I would think sticking to radius arms is the easiest/most-predictable-outcome. I guess if you're running 8" inches of lift the angles would be too steep for radius arms and you'd have to run a drop bracket on the frame side?



Thing is, I may be within spec, may not. Upper links to the frame is always more control.
 
4 link will have slightly less bind making bushings last longer imo, dodge has been running a 4 link for 27 years now
 
4 link will have slightly less bind making bushings last longer imo, dodge has been running a 4 link for 27 years now

Yeah, Ford's run radius arms for how long as well?

How does it have less bind? I would expect a 4 link to have more bind as it goes through it's range of motion. Radius arm doesn't change.

I know it will keep the caster changes to a minimum and as said here, better AD/AS, which considering that I am putting bigger brakes on this for towing, etc, could be enough.
 
Radius arm requires bushings to flex in order for the axle to be in a position other than parrallel with the chassis (assuming you're not doing some wild shit and building asymmetrical arms for circle track or something like that). 4-link does not.

Think about what happens when you drive over something with one wheel.
 
Radius arm requires bushings to flex in order for the axle to be in a position other than parrallel with the chassis (assuming you're not doing some wild shit and building asymmetrical arms for circle track or something like that). 4-link does not.

Think about what happens when you drive over something with one wheel.

yeah, I had that thought after I posted. I was thinking about straight up and down, not Massachusetts potholes.
 
Little hi-jack here but here goes:

Would there be any issue with in-boarding the radius arm frame-mounts instead of being parallel with the frame rails? The idea would be to minimize tires rubbing on the radius arms at full-lock.

Thinking of building a set of radius arms with a slight angle built in so the mounts land directly under the frame rails.
 
Little hi-jack here but here goes:

Would there be any issue with in-boarding the radius arm frame-mounts instead of being parallel with the frame rails? The idea would be to minimize tires rubbing on the radius arms at full-lock.

Thinking of building a set of radius arms with a slight angle built in so the mounts land directly under the frame rails.

Trevor at WFO told me to just run my arms outside the frame, which would be an offset. My frame is 34" wide, OD.

Seems like a non issue to run inside or outside. WFO sells bent arms for the Toyota to Ford SD60 crowd, too.

For me, I decide to stick with my Radius Arms and mounts, since the pumpkin will hit the oil pan before the arm will hit the frame.
 
Little hi-jack here but here goes:

Would there be any issue with in-boarding the radius arm frame-mounts instead of being parallel with the frame rails? The idea would be to minimize tires rubbing on the radius arms at full-lock.

Thinking of building a set of radius arms with a slight angle built in so the mounts land directly under the frame rails.


What truck? On the '88 F250 and '78 W300 I've mocked up with, the radius arms land right under the ~38" frame rails already. Run a little more neutral wheel offset than stock, and I don't think you'll have much tire rubbing problems.

IMG_20171116_141208.jpg
 
It's going under a 78 F150 4x4. From center of one frame-rail to the other its 32.5" (about 34" from outside to outside). On my 2005 Super Duty Dana 60 center of the radius arm mount to the center of the other is 35.25" so there isn't much space to gain by going under the frame.

Thanks for sharing Grendel; not going to overthink this one and just run it outside the frame like you said.
 
It's going under a 78 F150 4x4. From center of one frame-rail to the other its 32.5" (about 34" from outside to outside). On my 2005 Super Duty Dana 60 center of the radius arm mount to the center of the other is 35.25" so there isn't much space to gain by going under the frame.

Thanks for sharing Grendel; not going to overthink this one and just run it outside the frame like you said.

Yeah, you have the same frame width I do. I'd run outside it, not inside. It's what I am doing, offsetting each frame bracket to the outside to get to factory axle bracket width. No way for them to rub.

I've had a few conflicting measurements on the bracket OD, but it's close enough everyone doing these says to send it and not think about it.


Individual brackets are ~85mm ID, 97.5mm OD, not counting the little flare out on the bottom. Meaning, pocket where the radius arm bolts in is ~85mm wide. Brackets are 38 7/8" outside to outside, 31 3/16" inside to inside.




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Notes for later - SD 60 radius arm mounts at the axle are 32 and 1/8" ID and 37 and 5/8" OD with a width of 2 and 6/8" wide.

The joints on the frame end are 2 and 5/8" wide. Frame is 34 and 1/8" OD.

So, I should kick my radius arm brackets at the frame out, 1.75" at the transmission crossmember bolts (give an 1/4" or so).

Seems like I don't have to stress bushings if I do this right?
 
Are you running the IH frame or the super duty frame?
 
It's going under a 78 F150 4x4. From center of one frame-rail to the other its 32.5" (about 34" from outside to outside). On my 2005 Super Duty Dana 60 center of the radius arm mount to the center of the other is 35.25" so there isn't much space to gain by going under the frame.

Thanks for sharing Grendel; not going to overthink this one and just run it outside the frame like you said.

So, here ya go. Pretty much your frame, stuffing a 35 up where a 38 will fit, until the pig hits my engine cross member.

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This is great stuff, thanks for posting it up. I think I might have to steal your frame-mount design. I was going to use the RuffStuff outriggers but I think that's just lazy of me.
 
This is great stuff, thanks for posting it up. I think I might have to steal your frame-mount design. I was going to use the RuffStuff outriggers but I think that's just lazy of me.

I had them cut by Gatsby Trucks. Allen Smith is awesome.

http://gatsbytrucks.com/

Allen Smith 804-815-4175
email [email protected]

They're my design, he'll cut and bend them for you. Tell him I said hello.
 
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