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How necessary to replace upper and lower control arms when upgrading rear suspension?

Sloth

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How necessary is it to replace the upper and lower control arms when upgrading the rear suspension? Are the stock control arms limiting articulation in the rear? Is it worth just replacing the lower set and leaving the upper set?
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kodiakisland

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Replacing at the very least the lower arms is one of the best things you will do to increase rear articulation. I would also include the rear track bar as well. Absolutely one of the best upgrades I've instantly noticed on the trail. Keeping both tires in contact with the ground will go a long way toward off road ability.

When I got mine, the lowers were all that were available, so that's all I've replaced so far. It was an immediate improvement. I'll eventually replace the uppers, and would do both now since there are so many readily available.
 

PWillette

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I replaced just the lowers simply for protection, the OEMs are pretty flimsy IMO. I went Fabtech...night and day difference. If lifting over 3" I'd be looking to do the uppers as well.
 

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Having done articulation testing on several lifted Broncos. The OEM arms were not the limiting factor in articulation. The suspension geometry and shocks are.

the stock OEM arms are fairly beef as I’ve-dragged them all over rocks and nothing bent. I replaced them because Gold is sexy (Metalcloak arms) and because in the future I may switch things to where the extra articulation possibility can be used. In the stock location, the coilover allllmost contacts the lower arm at max articulation. With some setups, it does contact. (Looking at you Radflo;).

For notes, my Bronco on MC rear arms scored a 520 CTI. The Bronco with OEM arms scored a 530 CTI… That’s not the fault of the MC arms, it just shows the arms arnt the limiting factor. My MC arms still had plenty of room left for flexing, they were just limited by my King shocks being at the end of their travel

The main benefit you’ll see from aftermarket arms is the ability to set pinion angle after lifting as well as center the axle. This is why I went aftermarket.
Now I’ve seen people on stock suspension claim they gained 1/2” more travel with changing over to MC arms with no other mods. This was claimed to have been done on a flex ramp. I’m not gonna say they were wrong but at 1/2” difference I’d also venture to suggest it was just a error in measurements or inconsistencies from the flex ramp.

All that being said, if you’re lifting your Bronco I do recommend at least the lower arms to help with proper alignment. Beyond that you don’t need them. Also get an adjustable trackbar and a relocation bracket. It helps re center the axle left to right and returns the trackbar angle to normal. I left mine stock and had bumpsteer. I added those components and bumpsteer went away.

EDIT: I forgot to add that with most aftermarket arms too you’ll get smoother articulation. So In a way that can be seen as better articulation because you don’t have to fight as much for it. It can also allow the tires to maintain contact with the ground easier. It’s minimal but it’s there
 
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Having done articulation testing on several lifted Broncos. The OEM arms were not the limiting factor in articulation. The suspension geometry and shocks are.

the stock OEM arms are fairly beef as I’ve-dragged them all over rocks and nothing bent. I replaced them because Gold is sexy (Metalcloak arms) and because in the future I may switch things to where the extra articulation possibility can be used. In the stock location, the coilover allllmost contacts the lower arm at max articulation. With some setups, it does contact. (Looking at you Radflo;).

For notes, my Bronco on MC rear arms scored a 520 CTI. The Bronco with OEM arms scored a 530 CTI… That’s not the fault of the MC arms, it just shows the arms arnt the limiting factor. My MC arms still had plenty of room left for flexing, they were just limited by my King shocks being at the end of their travel

The main benefit you’ll see from aftermarket arms is the ability to set pinion angle after lifting as well as center the axle. This is why I went aftermarket.
Now I’ve seen people on stock suspension claim they gained 1/2” more travel with changing over to MC arms with no other mods. This was claimed to have been done on a flex ramp. I’m not gonna say they were wrong but at 1/2” difference I’d also venture to suggest it was just a error in measurements or inconsistencies from the flex ramp.

All that being said, if you’re lifting your Bronco I do recommend at least the lower arms to help with proper alignment. Beyond that you don’t need them. Also get an adjustable trackbar and a relocation bracket. It helps re center the axle left to right and returns the trackbar angle to normal. I left mine stock and had bumpsteer. I added those components and bumpsteer went away.
Ramp testing aside, what I noticed from replacing my rear arms was I lifted the rear tires a lot less than before on the very same trails. Now, maybe the actual amount of articulation wasn't that much if measured in inches, but the ability to keep both rear tires on the ground was a huge advantage. My factory arms had hard, cracked rubber bushings that had very little give. Same with the rear track bar.

I imagine there are a lot of factors in play and results will vary based on your particular coilovers and the brand of control arms.
 
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popo_patty

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Ramp testing aside, what I noticed from replacing my rear arms was I lifted the rear tires a lot less than before on the very same trails. Now, maybe the actual amount of articulation wasn't that much if measured in inches, but the ability to keep both rear tires on the ground was a huge advantage. My factory arms had hard, cracked rubber bushings that had very little give. Same with the rear track bar.

I imagine there are a lot of factors in play and results will vary based on your particular coilovers and the brand of control arms.
Good point. The hardened rubber was definitely limiting your free movement. Definitely a factor to consider if your OEM bushings are shot or decayed. I edited my post right after posting to talk about the “freer flow” so to speak as well from certain aftermarket arms.
 
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Good information. Thank you all for the feedback! (y)
 

popo_patty

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For your viewing pleasure. Metalcloak arms and trackbar. Rockjock relocation bracket. King suspension tuned by Accutune



 

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Does anyone know what our pinion angle is supposed to be?

My pinion is 7.3 degrees and the driveshaft is at 6.

Longer lower arms would correct my pinion angle.

But I do not notice any issues.
 
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I am at nearly the same setup, and new to it for that matter:

Accutune custom tuned King Shocks (2.5)
Metal Cloak Lowers - set a hair longer then OEM for my initial alignment
Core 4x4 Crawler Adjustable track bar - dual Johnny joints.

The rear of the vehicle is much more supple to me. It is rotating and dropping / moving around in a much smoother fashion. The rear even droops a little on hard acceleration. It's subjective, but it just feels right !
 

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Having done articulation testing on several lifted Broncos. The OEM arms were not the limiting factor in articulation. The suspension geometry and shocks are.

the stock OEM arms are fairly beef as I’ve-dragged them all over rocks and nothing bent. I replaced them because Gold is sexy (Metalcloak arms) and because in the future I may switch things to where the extra articulation possibility can be used. In the stock location, the coilover allllmost contacts the lower arm at max articulation. With some setups, it does contact. (Looking at you Radflo;).

For notes, my Bronco on MC rear arms scored a 520 CTI. The Bronco with OEM arms scored a 530 CTI… That’s not the fault of the MC arms, it just shows the arms arnt the limiting factor. My MC arms still had plenty of room left for flexing, they were just limited by my King shocks being at the end of their travel

The main benefit you’ll see from aftermarket arms is the ability to set pinion angle after lifting as well as center the axle. This is why I went aftermarket.
Now I’ve seen people on stock suspension claim they gained 1/2” more travel with changing over to MC arms with no other mods. This was claimed to have been done on a flex ramp. I’m not gonna say they were wrong but at 1/2” difference I’d also venture to suggest it was just a error in measurements or inconsistencies from the flex ramp.

All that being said, if you’re lifting your Bronco I do recommend at least the lower arms to help with proper alignment. Beyond that you don’t need them. Also get an adjustable trackbar and a relocation bracket. It helps re center the axle left to right and returns the trackbar angle to normal. I left mine stock and had bumpsteer. I added those components and bumpsteer went away.

EDIT: I forgot to add that with most aftermarket arms too you’ll get smoother articulation. So In a way that can be seen as better articulation because you don’t have to fight as much for it. It can also allow the tires to maintain contact with the ground easier. It’s minimal but it’s there
I have a Badlands on 35x11.5 that I want to lift +2-2.25 front and +1-1.25 rear.
In your experience, for such a small lift, are rear trailing arms necessary to get a good alignment?
 

popo_patty

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I have a Badlands on 35x11.5 that I want to lift +2-2.25 front and +1-1.25 rear.
In your experience, for such a small lift, are rear trailing arms necessary to get a good alignment?
For that range you’ll be fine. As long as the lift sits true. At about 2” the trailing arms and track-bar become useful though at 1 1/2” you’d probably see the benefit with the track-bar to keep it all squared up if you notice any jittery feeling in the rear.
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