mattphillips90

Ive been looking at long arms. All 3 links have long arms but some long arms dont mention a 3 link system. So is it a square being a rectangle but a rectanlge not being a square? Are some long arms literally just longer arms while some change the whole suspension?

xjmarc

You have a couple of different types, 3 link, 4 link and the most common radius arms. All have their pros and cons and each mfg. is slightly different. Some have better ways of attachment and bushings than others as well. All will change the steering geometry from stock quite a bit.

mattphillips90

But does that mean all long arms are 3 or 4 link? Like if i wanted to upgrade my regular lift to long arms, do i just replace the lower control arms?

Lowrange2

No, you replace all 4 arms and either replace the entire transmission crossmember or add brackets to the frame rail for the arms to mount to.

Sounds like you need to do A LOT more reading...

Lead Foot

You have ALOT of tech and reading ahead of you. To really become educated on each subject you will have to do a lot of searching. I'll try to give you a general outline of each setup.

You can not generalize the terms long arm and 3 link or 4 link together. 3 link, 4 link, radius arm, and triangulated 4 links are all types of suspension systems. Short arm, mid arm, and long arm are part of a description of that system.

Let's start easy. As a general statement, Stock fixed arms, aftermarket fixed arms, and aftermarket adjustable arms are all known as short arms. I would say that an arm with a length anywhere between 14" and 20" is a short arm. 20"-29" are mid arms. And 29"+ are long arms.

Now. To figure out a standard link system you count the Links in the direction from front to back but not the pan hard (track bar) when applicable. 3 links, 4 links, and radius arms have links that run near parellel front to back (less then 25 degree triangulation) therefor they require a pan hard to locate the axle side to side. A triangulated 4 link has links with overall triangulation exceeding at least 40 degrees preferably. Because of this they don't need a pan hard. NOTE- you should not run standard mechanical steering using a drag link combined with a trangulated link system.

4 Link-
So as read above. The XJ stock front suspension system is a 4 link. Though the stock system is made with weak, flimsy arms; it is still a decent system for a stock rig. Once you start lifting it and putting bigger tires on the rig, you will find that your tires sit further back in the wheel well, you may have issues properly adjusting caster, and the weak arms don't hold up to the off road abuse you are throwing at it. This is where slightly longer aftermarket fixed arms and fully adjustable arms come in to play. These are usually a very strong upgrade over stock and do very well at relocating the the axle back to its proper location in the wheel well as well as offering more caster adjusting possibilities. Note that all of these setups are still short arm 4 links. There are also a few companies that offer a 4 Link Long Arm Kit. They hold the same basic suspension design but offer longer control arms with new mounting lcoations on the frame side, sometimes equipped with a higher strength crossmember.
Pros - 4 links to hold axle in position front to back therefor will hold up better to a high speed rough impact after catching some air through the dessert. The 4 links attach at 4 seperate locations on the frame and on the axle. With proper geomtery your caster will stay somewhat consistent.
Cons - Generally speaking, they dont offer as much flex because of the inherent bind between the pan hard bar and 4th upper link. Because of this at least 2 of the joints in a 4 link system must be "soft joints" (rubber or poly instead of heim joints or rebuildable johnny style joints) This bind reduces flex and also decreases soft joint life. Possible clearance issues between upper arms and drivetrain in a long arm set up.
Uses - Equipped on most stock vehicles where flex isnt a concern as well as high speed desert racing vehicles where really high strength is a greater concern over flex.

Radius Arms-
One of the most popular after market, long arm suspension systems sold are radius arms. This is most likely because of their more simplistic design. A radius arm set has 2 lower control arms just like a 4 link and 2 upper control arms. BUT, these 2 upper control arms do not attach to the frame at their own location, but instead about 1/3 of the distance down the top of the lower arm. The whole axle "swings" or pivots off of the 2 frame mounting points. This causes the pinion and caster angle to change drastically in any long travel suspension system, which we are all going for right? Because this system has 4 control arms, some mistake as a 4 link and even some manufactures have even advertised it this way. Dont be fooled.
Pros - Cheaper to fabricate thus cheaper to buy. Lesser possiblity of clearance issues between control arms and drivetrain since the upper arms dont go all the way back to the frame. Generally easier to install because of only needing 2 attachment points at the frame.
Cons - Just like a 4 link, they dont offer as much flex because of the inherent bind between the pan hard bar and 4th upper link. Because of this at least 2 of the joints in a 4 link system must be "soft joints" (rubber or poly instead of heim joints or rebuildable johnny style joints) This bind reduces flex and also decreases soft joint life. The caster also changes drastically throughout travel.
Uses - Stock applications and long arm upgrade kits for the novice builder where cost, simplicity, and ease of installation is a concern.

That's enough for now. I will continue when I get to a computer and not on my phone. Lol

mattphillips90

Wow a lot of good info! So a basic short arm setup that comes stock on the jeep. Is it a 4 link? 4 control arms and the need for track bar or does it not count because of the degrees of the arms?

SeriousOffroad

No, the stock configuration is actually a 5 link. The 5th link is the trackbar. There are no kits on the market that are true 4-links.

In order to eliminate the trackbar you'd have to build a double triangulated system, and that's no small task.

Lead Foot

Correct. Standard 4 link. Once you go beyond somewhere around 20 degrees (rough guess) a pan hard will actually bind the suspension system, but without a pan hard the links will be susceptible to a high amount of stress when trying to locate the axle side to side. Thats why I specified less then 20 degrees plus pan hard and more then 40 degrees minus pan hard for a triangulated 4. there's a 20 degree "grey area" there where one system or the other MIGHT work but wouldn't be nearly ideal.

Lead Foot

You're going to confuse him man... YES there are FIVE links but it is not identified as a 5 link, rather a 4 link. The general consensus is YOU ONLY COUNT THE LINKS RUNNING NEAR PARELLEL FRONT TO REAR.

mattphillips90

Ahhhh ok ok ok its all starting to make sense. So most standard long arm kits will still use a pan hard bar? So whats the missing link between a 3 and 4?

Lowrange2

ALL production long arm kits use a track bar.

The missing link between the 3 and 4 link is one of the upper control arms...

My 3 link has two lower control arms, one upper driver side control arm and a track bar.

mattphillips90

Nowwww i got it. So i must ask, why no passenger ca? I know that 3 links are better for crawling so i understand that one less arm gives your axle more freedom but is that it? And I guess 3 links arent the safest for daily driving

Lead Foot

Sorry if Im leaving you hanging, I am going to work on the other suspenion descriptions when I get some more time.

There is nothing true about 3 links being unsafe for daily driving. That is a common misconception. I daily drove my last 3 jeeps on 3 linksand so have many others.

Lowrange2

Drive my 3 link down the highway all the time.

I just wouldn't suggest making that upper link out of PVC or anything similar.

Lead Foot

Haha! Why no PVC you ask? Ill be sure to touch on that in the description!

Yep, no problem down the highway, I have actually driven my jeep lifted 6.5" on 35s over a winding mountain pass hitting speeds of 90 mph. No problems, and dare I say no sway bars either?...