i was looking at suspension systems and have seen a lot of debate about them. i dont really know what is better or what exactly the differences are so some schooling would be appreciated. i know what a 3 and 4 link front setup is but what i was wondering what exactly a radius arm setup is and why alot of guys bash it. i was looking at iron rocks " iron y" kit and rk's kit and was just trying to figure out the differences. also why would u run a 3 link instead of a 4 link especially when jeeps are notorious for death wobble. im not looking to start a suspension battle im just trying to learn a little bit about each one and get a few experienced opinions about them.
Death wobble does not come from your arms, it comes from worn out parts or poor geometry. More often than not, it seems to be caused by bad balljoints.
Just to touch on these but not get into detail..
Stock XJ suspension is a 5 link, or 4 link with panhard (trackbar). When you articulate the suspension, the trackbar moves your axle left and right - depending on how your suspension is setup, it may move the axle several inches. With 4 control arms, the twisting, plus shifting sideways, causes the links to bind up and you will have your suspenion flex limited.
A 3 link with panhard removes one of those links from the equation and removes the binding. You get more articulation. Also, it is easier to package - if you aren't running a stock style setup, sometimes finding somewhere to put two upper control arm mounts can be very difficult - the driveshaft or exhaust get in the way.
A 4 link uses triangulation and not a panhard to keep the axle location in place. You dont get the side to side movement with suspension travel which can be optimal for go-fast driving, and there is very little binding so you can get a LOT of articulation - but the setup has its own drawbacks.
A Y link or Radius arm suspension hooks the upper arm to the lower arm (or just has one welded arm), so its effectivly a 2 link plus panhard. easy to package, and you don't get binding up up/down movement, but do get a lot of binding on articulation (the axle wants to twist a little, and this will not accomodate it).
You can learn a LOT reading on pirate. If you have questions, and articulate your (technical) question well, the responses can be a wealth of knowledge. Forget the forums for now, start with the BillaVista tech page. Read there for a couple of days - he does not answer the specific question you asked, but you will walk away more prepared to ask the questions you need.
http://www.pirate4x4.com/tech/