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will build 4-link longarms, who can help?

amazin-red

NAXJA Forum User
Location
at home
Hi,

I've done a lot of searches around the forum, but I could not fount what I expect.
My plan is to build up a 4-link longarm suspension on my rig, but I'm not shure about the dimensions of the arms, and their mounting points.

I would not like to again invent the wheel, so is here somewhere who buil up his own 4-link (I think some does it already), and could help me with some measurements, drawings or what else?

Thanks in advance, and have a nice weekend!

Rgds Red
 
Go do a search at www.pirate4x4.com or rockymountainextreme.com

There are several 4 link engineeing calculaters floating around...

http://rockymountainextreme.com/forum/showthread.php?t=13634

This was my friends first four-link...it may give you some ideas of what to do and what not to do...

If the link doesn't work try searching for all posts under "patriot"...the title of the thread is..."Finally!! started my xj project!!"
 
@Paul, sorry, this question is regarding the front, for the rear I'am thinking in the Tera coil conversion. I get it very cheap, so I need only to build the front myself.

@DA, thanks, I will search for this hints!
 
What you are attemping to do is not easy. Make sure you have a very good reason for doing it, hopefully because of the type of wheeling you do, the performance you are after, and the fab skills that you already possess.......and not because it's cool.

Here's a suggestion, FWIW. Consider a front three link, which is easier to design and build, and can work better than a four link. I'm talking about a real three link, not a triangulated three link or a radius arm. Since you are starting from scratch, seriously consider a mid arm, which also is easier to design and build than a three or four link long arm. The mid arm can give you the same performance without the loss of ground clearance that is typical with long arms. The mid arm can also be a three link, which can have advantages over a four link.

Since I've gone this far, let me give some advantages of the three link over the four link. It's nearly impossible (maybe totally impossible) to build a four link in the front of an XJ that doesn't bind at some point, requireing the use of some rubber bushings. With regular extreme articulation those rubber bushings wear out. The rubber bushings also allow some axle wrap in hard use, and this tendancy to wrap is increased as the bushings wear out. A three link will not bind at any point of axle movement, until the arms just can't move any more.....till then there is no bind whatsoever. This allows the use of hard joints, like rod ends or johnny joints, which will eliminate any axle wrap and usually last longer than rubber bushings. Also, the three link is much easier to design properly in the space that's available under the front of an XJ.

Food for thought. Good luck, and have fun, :)
 
@Goatman, I hope you will not think I am cracy, but I could not follow you, about the third link.

The both LCA in long design are easy, but the third...

From where to where it is mounted?
From the middle of the axle to where?

The skill for this I have, (and a good buddy to help also) only the right design is missing so far.
I run currently through the web, and steal any idea or hint I can find.

Thanks for the help

Rgds Red
 
Since it is for the front...hmmm...some have tried a wish bone configuration so that the UCAs can clear the oil pan...that way you would have some nice flex and droop in the front and probably the least bit of binding and it would be a true 3 link not a 4 link.... Also, many have tried the usual 3 link with your upper coming off of your LCA. I wouldn't recommend it but some would swear by it...personally, depending on how much wheeling you do, I would use the teraflex LCA upgrade kit and put my UCA where the LCAs were previously located...You would havwe to fab your UCA and brackets but that would probably be the easiest route...
 
I should have read Goatmans thread....He's got it in a nutshell...For superiority I would follow his advice..
 
amazin-red said:
@Goatman, I hope you will not think I am cracy, but I could not follow you, about the third link.

The both LCA in long design are easy, but the third...

From where to where it is mounted?
From the middle of the axle to where?

The skill for this I have, (and a good buddy to help also) only the right design is missing so far.
I run currently through the web, and steal any idea or hint I can find.

Thanks for the help

Rgds Red

When the upper arm is connected to the lower arm, rather than to the frame, this is a radius arm. This type of radius arm can have an upper arm on both sides or just on one side, it's still a radius arm design. A triangulated suspension can have four links, or it can use one U shaped or V shaped link that has one attachement point at the axle and two attachment points on the frame (one on each side). This is called a triangulated suspension, and does not need a track bar. It also can be difficult to design a good steering system with this design, causing many to go to full hydraulic steering with a front triangulated suspension.

I assume that you are talking about a four link, with two lower arms and two upper arms, all of them attached to the frame, and using a track bar. It is very tight under the front of an XJ to do a four link long arm. What I'm talking about is a three link, with two lower arms and one upper arm, all of them attached to the frame, and the upper arm on one side or the other.

What I mean by mid arm is something between the length of short arms or long arms. The goal is to get better arm angles, which is what longer arms accomplish. I never get why poeple have to go to very long arms if they don't want the short arms. A somewhat longer arm, with improved mounting locations, is very effective and does not reduce ground clearance like so many long arms do. If a person is limited to what can be bought, then it's either long arms or short arms, but if you're going to fabricate it yourself, and starting with a clean sheet of paper, I see little reason to build long arms, unless you're working with parts that you already have and are looking for a way to make them work. Long arms can work very well, don't get me wrong, but a design that does not compromise ground clearance is VERY difficult to build in the space allowed under the front of an XJ, and very few have been able to accomplish it. A mid arm three link is a much more practical design on the front of an XJ.

Obviously, this is what I have, so here are some pics for you. These pics are with 7.5" of lift and 35" tires.

standard.jpg

standard.jpg

standard.jpg

standard.jpg
 
BrettM said:
Richard, how long are your lowers? it looks to me like the new body side mounts you made are in the same spot as stock...?

You can actually make a big difference within the stock mounting area. I pretty much copied Richard's mid arm, except that I retianed both uppers & therefore made my uppers & lowers the same length to reduce binding. I kept my lower mounts 100% on the 45 degree part of the frame so that I wouldn't lose any clearance. With this I was able to extend my LCA mounting point about 2.5" back from stock, while the back of my LCA mount is no further back than stock, I also reduced my control arm angles from about 26 degrees to about 13 degrees. If anything I might have gained a .25" clearance over stock. I extended my UCA's a little more than my lowers, since stock they are an inch or so shorter.
The only thing I would differ from Richard on is that IMO it was a LOT of work. Just cutting the stock upper & LCA mounts off took forever.
Paul
 
MaineZJ said:
Go with a radius arm system like Clayton makes.

Yeah.......why?


:rolleyes:
 
BrettM said:
Richard, how long are your lowers? it looks to me like the new body side mounts you made are in the same spot as stock...?

My lowers are 19.5" long. The lower arm frame mounts are 2.5" further back and 1" lower than the stock mounting position. One of the reasons the arms have a good angle is that the axle mounts have been moved up quite a bit, they are even with the axle. The upper arm axle mount was also moved up quite a bit.
 
Goatman said:
Yeah.......why?


:rolleyes:

you don't have to build the UCA mounts.
make one of the radius arms removeable, gets lotsa flex
it's a proven design, lots and lots of GC and TJ guys use it
 
MaineZJ said:
you don't have to build the UCA mounts.
make one of the radius arms removeable, gets lotsa flex
it's a proven design, lots and lots of GC and TJ guys use it

But the stock short arm configuration works better, at least for off-road use, & all it requires is buying some quality arms.

Paul
 
MaineZJ said:
you don't have to build the UCA mounts.
make one of the radius arms removeable, gets lotsa flex
it's a proven design, lots and lots of GC and TJ guys use it

You obviously haven't read the previous posts in this thread. The question was about building a four link, not using radius arms. No offense to the Clayton people, or those who have bought and run the kit, but for someone willing and able to build something themselves the Clayton design is not very good. Proven design? Proven for what, to be durable? To unload on steep climbs, and to get hung up easily?

:rolleyes: :rolleyes: :rolleyes:
 
Hi all,

thanks in the first for all the comment, specially to Goatman, for the excellent "newbie-safe" description of a "three-link" suspension.

Well, I have to say that now, 2 days after my question about the 4-link system, it would better be to ask for the "best" LA system, but this question could not be ansered by more than one person.

Maybee it helps to answer first WHY I would like to change my current setup to a LA system, this goes fast:
flex_front.jpg


This is the current flexing, and I think that I am at the end with this LCAs. (procomp)

Now after reviewing your comments here, I think about in doing a system with radius arms maybee, because I understand the problem with a 4-link, and my head would not trust a three-link?!

Next question, a system like the "long arm upgrade" from Tera, does it work correctly, regarding to the amount of time to build it up, or is this a complete "misdesign"? I have a bad feeling, to interchange only the LCAs against Longarms, and do not touch the UCAs?!

What do you say?

Rgds Red
 
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