Need Help With Lower Control Arm Sizing

Cody Brought said:
I'm building the jeep mainly for cruising offroad and doing small jumps, not much rock crawling is planned at all
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Cody Brought said:
FYI this is my DD and I have cast outer knuckles, so i will not be doing any impressive jumps, mostly high speed cruising offroad and hitting bumps
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Cody Brought said:
Running 33's, plan to get 35's later
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So with your anticipated usage as described above, why are you doing any of the stuff you are doing? Trusses, long arms, why?

You state a bunch of theoretical advantages connected to your mods. But those mods will not solve any problem that you've stated or any problem that might result from your intended usage.

The most likely result of the mods you seem intent on doing is to fuck up your suspension and add a bunch of unsprung weight that provides no benefit within the scope of your intended usage.

If you are not just here to troll, spend some time reading the many many threads on suspension, what works, what doesn't, and why. You keep saying you want to learn but seem resistant to the advice offered. Without knowing what problem you need solved, how can any advice be properly targeted?

My favorite question: what problem are we trying to solve?
 
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astjp2 said:
Your assumption is founded, but if you do some research with real knowledgeable people not trying to sell you something it may change your mind. Control of the vehicle cannot be fixed by control arm length, shocks are 90% of the ride quality and road handling stock geometry is adequate for 80% of most drivers. Those others who need that extra can get by with a midarms. Do some searching on here and you can see the discussions and make your decisions for your build. Good luck 🍀
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I appreciate your advice, but my reasoning for the increased length is to increase the strength of the system. Id like for better ride quality, but that isnt my main concern.
 
Cody Brought said:
I appreciate your advice, but my reasoning for the increased length is to increase the strength of the system. Id like for better ride quality, but that isnt my main concern.
Click to expand...

What specific strength do you believe is lacking? And how do control arms address it?
 
g.hayduke said:
So with your anticipated usage as described above, why are you doing any of the stuff you are doing? Trusses, long arms, why?

You state a bunch of theoretical advantages connected to your mods. But those mods will not solve any problem that you've stated or any problem that might result from your intended usage.

The most likely result of the mods you seem intent on doing is to fuck up your suspension and add a bunch of unsprung weight that provides no benefit within the scope of your intended usage.

If you are not just here to troll, spend some time reading the many many threads on suspension, what works, what doesn't, and why. You keep saying you want to learn but seem resistant to the advice offered. Without knowing what problem you need solved, how can any advice be properly targeted?

My favorite question: what problem are we trying to solve?
Click to expand...

Im not trolling, and the reason im hesitant to take advice is because I dont know the true experience people have on the subject

The problem im solving is Im redoing my control arms and wanted to know if 2” .25 wall DOM tubing is sufficient for lowers. Someone said it is, so thats my question answered. Im well knowledgable on suspension geometry but i like to hear what people with experience have to say. Everything else related to my modifications is for a welding project in my highh
g.hayduke said:
So with your anticipated usage as described above, why are you doing any of the stuff you are doing? Trusses, long arms, why?

You state a bunch of theoretical advantages connected to your mods. But those mods will not solve any problem that you've stated or any problem that might result from your intended usage.

The most likely result of the mods you seem intent on doing is to fuck up your suspension and add a bunch of unsprung weight that provides no benefit within the scope of your intended usage.

If you are not just here to troll, spend some time reading the many many threads on suspension, what works, what doesn't, and why. You keep saying you want to learn but seem resistant to the advice offered. Without knowing what problem you need solved, how can any advice be properly targeted?

My favorite question: what problem are we trying to solve?
Click to expand...

g.hayduke said:
So with your anticipated usage as described above, why are you doing any of the stuff you are doing? Trusses, long arms, why?

You state a bunch of theoretical advantages connected to your mods. But those mods will not solve any problem that you've stated or any problem that might result from your intended usage.

The most likely result of the mods you seem intent on doing is to fuck up your suspension and add a bunch of unsprung weight that provides no benefit within the scope of your intended usage.

If you are not just here to troll, spend some time reading the many many threads on suspension, what works, what doesn't, and why. You keep saying you want to learn but seem resistant to the advice offered. Without knowing what problem you need solved, how can any advice be properly targeted?

My favorite question: what problem are we trying to solve?
Click to expand...

i stated the problem im solving and im hesitant to take advice when there isnt any more information to back it. However I ask further to learn more about it.

To be more direct; my main concern is the strength of my dana 30 front axle. If I were to land hard on it offroading i fear i will bend it, or the small flexing over time will wear stuff out faster. Another concern is since my control arms are at a high angle since i have a 4” lift, they transfer more load to my frame and make it harder to climb obstacles.
 
Cody Brought said:
The problem im solving is Im redoing my control arms
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Sorry, but that is not a problem. "Redoing" your control arms would generally be done to address a specific problem or, in other words, a solution to a problem, which I am 99.9% sure you don't have.

I'm not really knowledgeable on suspension geometry and sorry but neither are you. If you were knowledgeable, you would recognize the value of being able to place the upper frame mounts higher which a body lift enables you to do.

And you would not be so hung up on theoretical benefits of long control arms that you read about or saw in a marketing video or parroting of same BS.
 
Cody Brought said:
.... Im well knowledgable on suspension geometry but i like to hear what people with experience have to say. ...
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What do you know about instant centers, vertical separation, and antisquat? Everything else you have brought up about suspension geometry is either wrong or misguided.
 
I feel bad for new guys like cody. Don't worry, they treat everyone like this . To answer your very simple question, Yes 2" OD 0.25 is plenty for a lower control arm, It will take a serious beating. 1.5" OD .125 is plenty for uppers. They are not likely to receive a deflection that would cause them to bend. Happy fabricating.
 
Cody Brought said:
How do the shocks play into my vehicles strength? And what type of shocks should I get that would fix my issue?
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Good shocks (ie something like custom tuned Fox 2.0) can address several of the shortcomings of a lifted TJ.

Cody Brought said:
I dont have any body lift, only a 4” spring lift. How does the body lift help with my link separation?
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To get the most ideal geometry in the rear the upper link is going to want to occupy the same space as the package shelf without severely limiting up travel. That is why pretty much all “bolt on” long arm kits leave a lot to be desired as they sacrifice good geometry for easier packaging.
 
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Cody Brought said:
I appreciate your advice, but my reasoning for the increased length is to increase the strength of the system. Id like for better ride quality, but that isnt my main concern.
Click to expand...

There are plenty of Tjs running stock lengths with no issues concerning strength. The only reason to change anything with the control arms is to change their geometry and thus how engine torque at the axle reacts with the chassis.

Cody Brought said:
Im not trolling, and the reason im hesitant to take advice is because I dont know the true experience people have on the subject

The problem im solving is Im redoing my control arms and wanted to know if 2” .25 wall DOM tubing is sufficient for lowers. Someone said it is, so thats my question answered. Im well knowledgable on suspension geometry but i like to hear what people with experience have to say. Everything else related to my modifications is for a welding project in my highh
Click to expand...

The true answer to that depends on the arms length. Arm lengths over 24 inches will want 2.0 tubing but under 24 inches something in the 1 1/2 to 1 5/8 would be more than adequate and save weight.
Cody Brought said:
i stated the problem im solving and im hesitant to take advice when there isnt any more information to back it. However I ask further to learn more about it.
Click to expand...

May I suggest taking some time and check out the dozens of threads on here discussing many of the aspects you are asking about and the build threads where folks are putting those discussions to practice.
 
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kmas0n said:
I feel bad for new guys like cody. Don't worry, they treat everyone like this . To answer your very simple question, Yes 2" OD 0.25 is plenty for a lower control arm, It will take a serious beating. 1.5" OD .125 is plenty for uppers. They are not likely to receive a deflection that would cause them to bend. Happy fabricating.
Click to expand...

Well, to keep it in context, 2x.250 DOM would work for a stock length lower control arm, but Cody is talking about going to a longer arm (leaving aside whether or not it is warranted in this case).

Material requirement is driven in part by the length of the arm. On my rig, for example, a 2x.250 lower arm would fold like a toothpick.

Hang in here, Cody. Lot’s of good into to be had from very knowledgeable people here. But you sometimes need to be willing to leave your preconceived notions at the door.
 
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jjvw said:
What specific strength do you believe is lacking? And how do control arms address it?
Click to expand...

I have a large angle on my control arms, and because of that, forces exerted upward on the axle are directed sideways because the control arm moves the axle on a relatively wide arc. That sideways force is also directed through the control arm and into the frameside mount. This shouldn't be a problem, but since I want to do small jumps and this is my DD, id like to have the peace of mind. It would also marginally increase the ride quality because more force is directed to the spring.

My qualifications for physics is a high school credit, so take all information with a grain of salt
 
kmas0n said:
I feel bad for new guys like cody. Don't worry, they treat everyone like this . To answer your very simple question, Yes 2" OD 0.25 is plenty for a lower control arm, It will take a serious beating. 1.5" OD .125 is plenty for uppers. They are not likely to receive a deflection that would cause them to bend. Happy fabricating.
Click to expand...

I really appreciate your answer and your kindness. I found sparse information on the control arms specifics so I figured Id log in and create a thread. I understand that everyones looking out for me, and I dont expect them to be patient with me because im new to threads.

Thank you!
 
jjvw said:
What do you know about instant centers, vertical separation, and antisquat? Everything else you have brought up about suspension geometry is either wrong or misguided.
Click to expand...

Im shooting for at least 8.75" of vertical separation of my mounts because the biggest tire ill run is a 35. I know a little about my centers and the anti squat/dive, but not enough to put this together myself and know what they will be. Thats why im taking measurements now and plugging them into a 4 link calculator.

Do the calculators work? Or should I study the antisquat and dive more as well as instant centers?

What else did I get wrong about suspension geometry if your willing to list it. I appreciate the criticism
 
g.hayduke said:
Sorry, but that is not a problem. "Redoing" your control arms would generally be done to address a specific problem or, in other words, a solution to a problem, which I am 99.9% sure you don't have.

I'm not really knowledgeable on suspension geometry and sorry but neither are you. If you were knowledgeable, you would recognize the value of being able to place the upper frame mounts higher which a body lift enables you to do.

And you would not be so hung up on theoretical benefits of long control arms that you read about or saw in a marketing video or parroting of same BS.
Click to expand...

I am relatively knowledgeable on 4 link suspension geometry, the main areas im unclear in are centers, antisquat, and antidive, but I plan to research it a bit more from what ive learned here. However, im using a calculator so its not a great concern.

I recognize the benefits of a higher upper control arm mount, and I had to do that anyway because my rear truss goes over my diff. I said id set my bumpstops accordingly until i figure it out.

What ive learned has not been from any video trying to sell me something, its been from people building their jeep explaining the pros and cons of longer control arms. I figured since i was trussing my axles and increasing my link separation, id also build my own control arms to help with my ride a little but mostly for strength. Since I was doing that, why not move my frame mounts back. Im cutting them off anyway for my rust repair plates.

All I asked for was advice on the sizing of my control arms, and I explained my modifications and intended usage so people could give me an educated opinion. I really appreciate all advice and criticism because it makes me think and gives me more information.

If your not knowledgeable on suspension geometry, dont tell me im not either. If you dont understand it, dont bash me. I want respectful thoughts, which everyone else has given.
 
Blackjack said:
Good shocks (ie something like custom tuned Fox 2.0) can address several of the shortcomings of a lifted TJ.



To get the most ideal geometry in the rear the upper link is going to want to occupy the same space as the package shelf without severely limiting up travel. That is why pretty much all “bolt on” long arm kits leave a lot to be desired as they sacrifice good geometry for easier packaging.
Click to expand...

Im triangulating the rear upper control arms and cutting out the old upper link and trackbar mount. So at least the links wont interfere with my fuel lines, but ill look into a bodylift soon and make sure i can easily adjust my bumpstop when I do that.

Ill look into nicer shocks and see what benefits those will provide. Although it might be a little until i get some, they are expensive. Thank you for all of your help, I didnt think as much about shocks as I shouldve.
 
NashvilleTJ said:
Well, to keep it in context, 2x.250 DOM would work for a stock length lower control arm, but Cody is talking about going to a longer arm (leaving aside whether or not it is warranted in this case).

Material requirement is driven in part by the length of the arm. On my rig, for example, a 2x.250 lower arm would fold like a toothpick.

Hang in here, Cody. Lot’s of good into to be had from very knowledgeable people here. But you sometimes need to be willing to leave your preconceived notions at the door.
Click to expand...

What ive learned is that shocks will be more important than the arms in terms of ride quality, and for a 4" lift stock length arms would be okay.

I should restate my reasoning and ask a new question to clear some stuff up.

Im trussing my axles so they can withstand the higher forces im putting on them. The front Dana 30 wont do well without it, and while the rear 44 could probably go without a truss, I wanted to experiment with triangulating my upper mounts to remove the trackbar, since the raised mount is dangerously close to my fuel lines and it makes my tire get real close to my spring.

This is for a school welding project, thats the main reason im starting this work.

Im welding frame repair kits on too, and the control arm area plates require the arms be cut off, so I will be making new 1/4" steel ones.

Because I wanted to switch from the rubber joint arms to a rebuildable enduro joint setup, I wanted to make new arms.

My new question: Considering the backstory given and the intended use of the vehicle, is it worth building longer arms?

After adding up the prices, I want the answer to be no, which it seems like people think so.

What benefits would longer arms have? and what drawbacks. My arms are adjustable currently, so should I build the trusses, adjust my front accordingly, and just make 2 upper arms that are the same length as the lowers for my triangulation?

You all have been a really great help with getting me to think about every aspect of my project, I greatly appreciate your time
 
Cody Brought said:
I have a large angle on my control arms, and because of that, forces exerted upward on the axle are directed sideways because the control arm moves the axle on a relatively wide arc. That sideways force is also directed through the control arm and into the frameside mount. This shouldn't be a problem, but since I want to do small jumps and this is my DD, id like to have the peace of mind. It would also marginally increase the ride quality because more force is directed to the spring.

My qualifications for physics is a high school credit, so take all information with a grain of salt
Click to expand...

The angle you have is the same as plenty of Tjs. If your plans are for playing hard you should really start with proper functioning bump stops and shocks. The axle arc with stock length arms really does not present real issues until you are over 11 inches of front shock travel up front and 12 inches in the rear.

Control arm angle does not start having a real effect on ride until you are well above four inches of lift.

Cody Brought said:
Im shooting for at least 8.75" of vertical separation of my mounts because the biggest tire ill run is a 35. I know a little about my centers and the anti squat/dive, but not enough to put this together myself and know what they will be. Thats why im taking measurements now and plugging them into a 4 link calculator.

Do the calculators work? Or should I study the antisquat and dive more as well as instant centers?

What else did I get wrong about suspension geometry if your willing to list it. I appreciate the criticism
Click to expand...

You need to understand that the calculator is a tool and is only as valuable as you make it. It’s accuracy is only as good as the data you provide and understand what it is showing you. For example most folks do not actually know their actual center of gravity so right off the bat your antisquat and roll axis will not be 100 percent accurate.

In order for you to understand what the calculator is showing you you need to understand the relationship between instant center, roll center, antisquat, and roll axis. A good place to start is here. https://wranglertjforum.com/threads/link-suspension-terms-and-reading-material.50637/
 
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Cody Brought said:
I am relatively knowledgeable on 4 link suspension geometry, the main areas im unclear in are centers, antisquat, and antidive, but I plan to research it a bit more from what ive learned here. However, im using a calculator so it’s not a great concern.
Click to expand...

The areas you are unclear on are the basics that must understand to truly be knowledgeable in suspension geometry.

Cody Brought said:
I recognize the benefits of a higher upper control arm mount, and I had to do that anyway because my rear truss goes over my diff. I said id set my bumpstops accordingly until i figure it out.
Click to expand...

If your upper axle mount is much above six inches from the axle tube with no body lift you will have to put in so much bumpstop you will have no up travel.


Cody Brought said:
What ive learned has not been from any video trying to sell me something, it’s been from people building their jeep explaining the pros and cons of longer control arms. I figured since i was trussing my axles and increasing my link separation, id also build my own control arms to help with my ride a little but mostly for strength. Since I was doing that, why not move my frame mounts back. Im cutting them off anyway for my rust repair plates.
Click to expand...
It sounds like you have been watching Dirt Lifestyle and Muddy Beards. While I like some of their content, their vids on long arm justification are just not truly applicable to a four inch lifted TJ. They have both built with much higher lift heights and larger rubber which changes a lot of parameters to maintain decent geometry.

Cody Brought said:
If your not knowledgeable on suspension geometry, dont tell me im not either. If you dont understand it, dont bash me. I want respectful thoughts, which everyone else has given.
Click to expand...

Just a fair warning comments like this will derail your thread with the quickness.
 
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Cody Brought said:
Im triangulating the rear upper control arms and cutting out the old upper link and trackbar mount. So at least the links wont interfere with my fuel lines, but ill look into a bodylift soon and make sure i can easily adjust my bumpstop when I do that.

Ill look into nicer shocks and see what benefits those will provide. Although it might be a little until i get some, they are expensive. Thank you for all of your help, I didnt think as much about shocks as I shouldve.
Click to expand...

So right off the bat you are violating the basics of good suspension. You do not adjust the suspension to things like fuel lines. You adjust the fuel lines, exhaust, and the like to work around the suspension. Packaging matters.

Yes good shocks are expensive. Properly designed and constructed link suspensions are more expensive.
 
Cody Brought said:
What ive learned is that shocks will be more important than the arms in terms of ride quality, and for a 4" lift stock length arms would be okay.

I should restate my reasoning and ask a new question to clear some stuff up.

Im trussing my axles so they can withstand the higher forces im putting on them. The front Dana 30 wont do well without it, and while the rear 44 could probably go without a truss, I wanted to experiment with triangulating my upper mounts to remove the trackbar, since the raised mount is dangerously close to my fuel lines and it makes my tire get real close to my spring.

This is for a school welding project, thats the main reason im starting this work.

Im welding frame repair kits on too, and the control arm area plates require the arms be cut off, so I will be making new 1/4" steel ones.

Because I wanted to switch from the rubber joint arms to a rebuildable enduro joint setup, I wanted to make new arms.

My new question: Considering the backstory given and the intended use of the vehicle, is it worth building longer arms?

After adding up the prices, I want the answer to be no, which it seems like people think so.

What benefits would longer arms have? and what drawbacks. My arms are adjustable currently, so should I build the trusses, adjust my front accordingly, and just make 2 upper arms that are the same length as the lowers for my triangulation?

You all have been a really great help with getting me to think about every aspect of my project, I greatly appreciate your time
Click to expand...

Unless you are trying to do some JeepSpeed stuff or some rock bouncing you really do not want or need the extra weight or hassle of trussing the axles. Adding control arm skids, weld washers and gussets to control arm mounts are all that is required.

Cool that you are getting some shop credit for working on your ride. Since it is involving actual frame repair your money would be best served investing in some of the frame repair sections that are available. That way you can get everything returned back to where it is to begin with. Then take some time to get out and use it. As your skills increase the Jeep will tell you what you need to modify next.
 
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