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Unread 04-30-2013, 06:32 PM   #1
PHARIS88
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why adjustable lower arms, and upper stock arms are bad idea?

Ok, my father is being stubburn and saying there is NO need to get both upper and lower control arms for my jeep. He wants to know why you can't just extend the lower arms and keep the stock upper arms.

I told him the pinion angle would be way off, he doesn't believe me, can someone please give me a detailed explanation WHY and HOW doing this would mess up the angles?

He says you can adjust the lower and lengthen them and keep the upper where they are at and the axle will still move forward and no need to spend more money on the uppers as well.

I'm going to buy both but I would like to have an explanation why that is a bad idea in PLAIN ol ENGLISH haha

Thanks yall

**ZJ has about a 4" lift, ALONG with death wobble which I am currently trying to fix, still stock wheels and 30X9.5X15 tires, which in a week I'll have new wheels and tires installed**

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Unread 04-30-2013, 07:17 PM   #2
ZJMatt
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Quote:
Originally Posted by PHARIS88 View Post
Ok, my father is being stubburn and saying there is NO need to get both upper and lower control arms for my jeep. He wants to know why you can't just extend the lower arms and keep the stock upper arms.

I told him the pinion angle would be way off, he doesn't believe me, can someone please give me a detailed explanation WHY and HOW doing this would mess up the angles?

He says you can adjust the lower and lengthen them and keep the upper where they are at and the axle will still move forward and no need to spend more money on the uppers as well.

I'm going to buy both but I would like to have an explanation why that is a bad idea in PLAIN ol ENGLISH haha

Thanks yall

**ZJ has about a 4" lift, ALONG with death wobble which I am currently trying to fix, still stock wheels and 30X9.5X15 tires, which in a week I'll have new wheels and tires installed**
The upper control arms work to "rotate" the axle, while the lowers control how far it is front-to-back within the wheel well. That rotation controls where your pinion yoke is, on an axis, thus affecting the angle that your driveshaft connects to it and the stress on the u-joints and pinion.

I ran a 3" lift with just lowers and about 20k miles later my rear bearings were howling. I attribute it to that, though it may have just been a coincidence with 215k+ on the jeep.
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Unread 04-30-2013, 07:27 PM   #3
PHARIS88
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Quote:
Originally Posted by ZJMatt

The upper control arms work to "rotate" the axle, while the lowers control how far it is front-to-back within the wheel well. That rotation controls where your pinion yoke is, on an axis, thus affecting the angle that your driveshaft connects to it and the stress on the u-joints and pinion.

I ran a 3" lift with just lowers and about 20k miles later my rear bearings were howling. I attribute it to that, though it may have just been a coincidence with 215k+ on the jeep.
Thank you!
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Unread 05-01-2013, 11:54 AM   #4
ratmonkey
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Either lower or upper arms can be used to set pinion angle. Though with stock upper arms you need to shorten the lowers instead of lengthen. That limits the tire size you can run even more and sucks the axle further back causing other issues with steering. If you lengthen them your pinion angle will be terrible and you'll have nasty vibrations that will eventually cause front axle pinion failure. You'll also end up with too much caster causing terrible handling characteristics and possibly worse speed related death wobble.

If you only get one pair of adjustable arms for the front, get upper, AND buy fixed lower arms. Or better yet, both adjustable. At 4" you've exposed every part of the stock suspension that's even slightly worn out to a lot of stress. Causing control arm bushings and the track bar to pretty much give up the ghost.
At your height, if everything isn't new you'll end with problems like death wobble. Get the full adjustable set including track bar and do it safely.
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Unread 05-01-2013, 12:36 PM   #5
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Originally Posted by ratmonkey View Post
Either lower or upper arms can be used to set pinion angle. Though with stock upper arms you need to shorten the lowers instead of lengthen. That limits the tire size you can run even more and sucks the axle further back causing other issues with steering. If you lengthen them your pinion angle will be terrible and you'll have nasty vibrations that will eventually cause front axle pinion failure. You'll also end up with too much caster causing terrible handling characteristics and possibly worse speed related death wobble.

If you only get one pair of adjustable arms for the front, get upper, AND buy fixed lower arms. Or better yet, both adjustable. At 4" you've exposed every part of the stock suspension that's even slightly worn out to a lot of stress. Causing control arm bushings and the track bar to pretty much give up the ghost.
At your height, if everything isn't new you'll end with problems like death wobble. Get the full adjustable set including track bar and do it safely.
Yeah I already have adjustable front and rear track bars, I am going to buy adjustable front upper and adjustable lower arms, just needed an explanation to pass on to my old man why doing just one was a bad idea.

Ordering front arms through kolak
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Unread 05-01-2013, 10:58 PM   #6
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Is this the same for the rear? The need to shorten the lowers? I got lower adjustables only for my 3.5 IRO lift and am now thinking I should get their uppers too? I just put oem uppers in I don't want to unnecessarily wear things in the driveline. My logic for the adjustable lowers was from all the other 3.5 or 4'' kits came with longer lower arms(RE, zone, RC)
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Unread 05-02-2013, 11:19 AM   #7
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Ordered adjustable front upper and lower control arms, now I'm sure I'll want to save another 300 or w/e for the rear :/
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Unread 05-02-2013, 01:09 PM   #8
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im at 4" lift and 31s, adjustable lowers with stock uppers.
adj. uppers from IRO are in the garage <-- last suspention parts on the list

any pointers on installing these? start fromt stock length and go from there?
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Unread 05-02-2013, 01:28 PM   #9
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Originally Posted by baldygo View Post
im at 4" lift and 31s, adjustable lowers with stock uppers.
adj. uppers from IRO are in the garage <-- last suspention parts on the list

any pointers on installing these? start fromt stock length and go from there?
I was planning on making them about 1/8-1/4" longer than stock and popping them in... and see how they fit... These will be the first control arms I will ever be installing so I'm sure something will come up lol
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Unread 05-02-2013, 02:07 PM   #10
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I thought I saw somewhere on here that if you have both upper and lower adjustable it's about 1/2'' more than stock, but closer to 1/4'' if you only have one or the other. I'm curious now about ratmonkeys comment. Actually making the adjustable arm shorter for only the lowers if you have oem uppers... I would love more input on that. Or if that applies to the rear just as much as the front...
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Unread 05-02-2013, 02:11 PM   #11
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Originally Posted by moparlover1992 View Post
I thought I saw somewhere on here that if you have both upper and lower adjustable it's about 1/2'' more than stock, but closer to 1/4'' if you only have one or the other. I'm curious now about ratmonkeys comment. Actually making the adjustable arm shorter for only the lowers if you have oem uppers... I would love more input on that. Or if that applies to the rear just as much as the front...
But then your axle and tires will be closer to your doors... and would have to run a smaller tire... I really want to push my front axle farther out front, maybe a tad bit more than center? like 1/4" - 1/2 inch more towards the front bumper

but hmm I'll start at 1/2 inch then and go from there

and right now I'm having steering issues with the axle sucked too far in to, which is why i broke down and just got both at the same time.
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Unread 05-02-2013, 02:15 PM   #12
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Quote:
Originally Posted by moparlover1992 View Post
I thought I saw somewhere on here that if you have both upper and lower adjustable it's about 1/2'' more than stock, but closer to 1/4'' if you only have one or the other. I'm curious now about ratmonkeys comment. Actually making the adjustable arm shorter for only the lowers if you have oem uppers... I would love more input on that. Or if that applies to the rear just as much as the front...
you push the axle in whichever direction makes the pinion angle right. for the front it's most likely shorter, for the rear it's longer.

you won't like the vibes if you don't set them right.
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Unread 05-02-2013, 02:25 PM   #13
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Originally Posted by PHARIS88 View Post
But then your axle and tires will be closer to your doors... and would have to run a smaller tire... I really want to push my front axle farther out front, maybe a tad bit more than center? like 1/4" - 1/2 inch more towards the front bumper

but hmm I'll start at 1/2 inch then and go from there

and right now I'm having steering issues with the axle sucked too far in to, which is why i broke down and just got both at the same time.
get both adjustables then. i did it and i still run with my front adjusted out at least an inch from factory.

if you go to far you'll know it because you'll run into steering issues
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Unread 05-02-2013, 02:27 PM   #14
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Originally Posted by ratmonkey View Post
you push the axle in whichever direction makes the pinion angle right. for the front it's most likely shorter, for the rear it's longer.

you won't like the vibes if you don't set them right.
You are talking about if you keep the uppers stock length right? I can adjust the upper and lower in the front to be BOTH longer than stock to push the axle out, and keep the pinion angle better.

B/c if I length the lower control arms and keep stock uppers I will have vibes and pinion angle will be bad/off.

I'm understanding this correctly right?
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Unread 05-02-2013, 02:29 PM   #15
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Originally Posted by JohnnyZJ View Post
get both adjustables then. i did it and i still run with my front adjusted out at least an inch from factory.

if you go to far you'll know it because you'll run into steering issues
Yeah I have both adjustable upper and lower fronts, coming in I ordered through kolak, figured I would lengthen BOTH by 1/2" and I should be fine.


Rear arms upper and lower are stock though
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