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Discussion Starter #1
I'm just curious...

Different manufacturers come up with different lengths for front fixed lower control arms. Does one know better than the others?

Teraflex are 22 13/16' (website says for 2.5-3" of lift)
JKS are 23" (website says for 0-4.5" of lift)
Synergy are 23 1/8" (website says for 0-4.5" of lift)

So all three would be great for a 3" lift right? But each will make my caster different. Who is right? Or is good caster a small range and all three will be in that range? And does it matter if you have a stock driveshaft vs a 1310?

For the record, I have MetalCloak 2.5" springs which netted me 3.3" of front lift and MetalCloak front lower adjustable arms that my Jeep alignment shop have set at 23 1/8". It rides good. Not looking to make a change. I am thinking about adjusting down to both the JKS and then Teraflex lengths just to see what kind of difference it makes.
 

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I'm just curious... Different manufacturers come up with different lengths for front fixed lower control arms. Does one know better than the others? Teraflex are 22 13/16' (website says for 2.5-3" of lift) JKS are 23" (website says for 0-4.5" of lift) Synergy are 23 1/8" (website says for 0-4.5" of lift) So all three would be great for a 3" lift right? But each will make my caster different. Who is right? Or is good caster a small range and all three will be in that range? And does it matter if you have a stock driveshaft vs a 1310? For the record, I have MetalCloak 2.5" springs which netted me 3.3" of front lift and MetalCloak front lower adjustable arms that my Jeep alignment shop have set at 23 1/8". It rides good. Not looking to make a change. I am thinking about adjusting down to both the JKS and then Teraflex lengths just to see what kind of difference it makes.
Adjusting your front lower CA's shorter than your current length of 23 1/8 will reduce caster and make straight line handling less stable.
 

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Discussion Starter #3
Adjusting your front lower CA's shorter than your current length of 23 1/8 will reduce caster and make straight line handling less stable.
Maybe, maybe not. If you are true and correct, that means both Teraflex and JKS are selling arms that do not increase caster enough which would seem strange to me.

Like I said, I am going to probably test this out some myself because of my curiosity. Meanwhile, anyone else that has experience and knowledge please chime in.
 

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All three would result in different caster readings if the upper CA length is the same.
All three could also have the same caster setting if adj. upper control arms were installed and used to dial in that setting.
 

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Maybe, maybe not. If you are true and correct, that means both Teraflex and JKS are selling arms that do not increase caster enough which would seem strange to me. Like I said, I am going to probably test this out some myself because of my curiosity. Meanwhile, anyone else that has experience and knowledge please chime in.
It's basic geometry.
 

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Maybe, maybe not. If you are true and correct, that means both Teraflex and JKS are selling arms that do not increase caster enough which would seem strange to me.

Like I said, I am going to probably test this out some myself because of my curiosity. Meanwhile, anyone else that has experience and knowledge please chime in.
Hmmm. Depends totally on your alignment numbers, namely caster. You want to balance, as well as possible, your caster and your pinion angle. So...I would say, without seeing your alignment numbers, that if you're around 4.5 degrees caster, then you won't really see an improvement in the balance that you already have. To me that's the sweet spot for both caster and pinion.

I would also keep in mind that there are variances from Jeep to Jeep, and that no 2 Jeeps will yield the same numbers with the same equipment. So really getting the caster number is where to start. With most fixed arms, it's "good enough", whereas with adjustables, you can really dial it in on the money and you're good. Depends on the wants of the vehicle owner.

P.S.

I see you're in Pearland. I'll be looking out for ya neighbor (up by Willowbrook here)!
 

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too much caster can cause your rig to handle like a boat and have negative pinon angle. 2.5" RK lift with about 2.75-3" actual lift up front

I had the Teraflex fixed arms and my caster was 3.3 and 3.4 it handled great.


I then added the alpine TF arms and adjusted them to 23" and was even better.
 

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too much caster can cause your rig to handle like a boat and have negative pinon angle. 2.5" RK lift with about 2.75-3" actual lift up front

I had the Teraflex fixed arms and my caster was 3.3 and 3.4 it handled great.


I then added the alpine TF arms and adjusted them to 23" and was even better.
That's quite a bump from the fixed.
 

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Discussion Starter #11
too much caster can cause your rig to handle like a boat and have negative pinon angle. 2.5" RK lift with about 2.75-3" actual lift up front

I had the Teraflex fixed arms and my caster was 3.3 and 3.4 it handled great.


I then added the alpine TF arms and adjusted them to 23" and was even better.

Great example from experience. Thanks JADMT.
 

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no help. not contributing. go home dude.
I beg to differ... This will probably be the best advice you will get. I have had 3 different sets of aftermarket control arms on his JK. 2 sets of fixed arms and a set of custom length adjustables. The fixed from well known companies with engineered systems that didn't handle well. If you are happy with how it drives and aren't suffering from any issues then why screw with it. unless you are trying to gain something you're just costing yourself $$$.
 

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too much caster can cause your rig to handle like a boat and have negative pinon angle. 2.5" RK lift with about 2.75-3" actual lift up front

I had the Teraflex fixed arms and my caster was 3.3 and 3.4 it handled great.


I then added the alpine TF arms and adjusted them to 23" and was even better.
^this
I just checked the length on my Synergy front lca's(I have adjustables), and my alignment shop got them at 23", I have 2" lift, 5.2-5.0* caster, drives great.

2016-03-16_08-08-32 by SilverFJ RSM, on Flickr
 

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It's just my opinion, but anything more than 2.5 and the TF's are a bit short. I think they are perfect for an RK 1.5...

I would use the Synergy for anything up to 3.5" and the JKS would be great at 2.5. Some Jeeps drive great at 3.2° caster and others wander all over the road. So I would want to be over 4° if I had the option.

I have an RK 2.5 and started with the TF arms and moved to the Synergy's. Wife noticed the difference in a good way. That's all that matters to me.

You can add the Superlift fixed arms to your list too... They are the longest of the bunch and just right for a 3.5" lift.
 

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Along the same lines as the front fixed CA, how about the rears. I can't find the actual lengths listed any where. Say, if you use a rear upper fixed, do you need the corresponding rear lower or is it actually stock length?
 

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Along the same lines as the front fixed CA, how about the rears. I can't find the actual lengths listed any where. Say, if you use a rear upper fixed, do you need the corresponding rear lower or is it actually stock length?
You can only run uppers by themselves. Longer lowers will rotate the pinion down. Yes lowers can be shortened but then the tire is pulled in toward the pinch seem.
Rears are not important unless running 4" of lift, or using a aftermarket DS (2 door)
synergy's rear are +.5 but require uppers as well (wheelbase + pinion)
 

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Along the same lines as the front fixed CA, how about the rears. I can't find the actual lengths listed any where. Say, if you use a rear upper fixed, do you need the corresponding rear lower or is it actually stock length?
most fixed lower rears are longer as are the uppers and really should get a set of rear upper adjustables to set the pinion. I have the tf fixed rears and I like them but if I had to do it over I would have gotten the adj upper alpines.
 

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I have a 2.5" JKS JSpec lift and installed the JKS J-Link Fixed Front Lower Control Arms. Uploading now and will post it soon. Have around 4.4 driver side front and 4.6 passenger side front. Factory wants the passenger side to have around 0.2 higher to combat the crown on the road which makes the Jeep pull to the right if Caster were to be exactly the same on both sides...
 

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