nick_n_ii

Ok we all know long arms are better.

I've been looking around at all the different kits. Trying to get idea's for building my own. And franky I'm a bit brain scrambled.

I'd like to know Pros and Cons to each of the below.

Radius Arms-

3 link-

Long lower only w/short upper(Tera flex style)-

True 4 long links-

Thanks for any and all input.

EndlessMtnFab

Radius Arms Pros: Simple to design & build. Cheaper to build.
Radius Arm Cons: Bushing wear due to binding. Tendency to "fall away" under heavy droop (both sides at the same time).


3 Link Pros: Pinion change thru axle cycle. Less stress on LCAs. No bushing/binding issue. More easily tuned.
3 Link Cons: Increased cost. Design time is higher if you don't understand the concepts. Space limitations depends on what drivetrain you run.


Long Lowers/Short Upper Thoughts: Amalagation at best. Better than a Radius Arm setup, but the short uppers exaggerate all the movements of the 3 link setup. The more lift, the harder it is to set it up becuase the UCAs are more aggressively sloped than the lowers leading to weird link placement issues.



True 4 Link Pros: Most flex. Most axle control. Greatest ability to tune. Eliminates the track bar.
True 4 Link Cons: Oil pan is in the way. Even more space issues than a 3 link. Takes the most time to design & build if you want to do it right.



Read my build thread for more thoughts & pictures. I went the 3 link route ......



Joe

nick_n_ii

Thank you for some very detailed in sites.

4.3L XJ

My opinion is that three link is the way to go. The way the stock four link is set up, there is the need for soft rubber bushings to compensate for changes in geometry as the axle articulates. Like Joe, I have a three link. It is the best of both worlds.

nick_n_ii

But isn't having 1 upper link a weak point?

Or do you over build that to keep it stronger?

muddeprived

I been wondering the same thing.

EndlessMtnFab

I wouldn't say you "over-build" it .... but you do need to account for the extra stress.


At the very least, consider upgrading the size of the UCA bolts.



If you are keeping the factory cast UCA mount .... replace it with a different bushing. You can get a different MOOG brand bushing, that with a little bit of work, will hold a 12 mm bolt. The factory bolt size is 10 mm.


Personally, I prefer even larger and went with a 9/16 bolt arrangement. That gave me access to more manufacturers joints/bushings/tabs/etc


The UCA I builtis 1.5 OD with a .250 wall. I would have preferred .188 (3/16) wall, but my local metal suppliers did/do not stock this size. The 3/16 wall is way more than sufficient for any single or double UCA arrangement you may choose.



Joe

89eliminator

in order to eliminate the tracbar, wouldnt you need to triangulate the arms? one would think so.

EndlessMtnFab

Yes ... that is automatically assumed that anyone building a 4 link will at least triangulate one pair of control arms. I didn't make any reference to triangulating in the post .... and will assume the OP (nick in this case) at least has a basic understanding if he is going to build something from scratch.


Personally, I prefer the double triangulated. But it's a pain and 2 halves to set it up quickly and the design has some other quirks you need to account for if you want to balance all things "perfectly." I've built them both ways with good results.



Joe

nick_n_ii

Ya, it was under stood in your post.

As for 3 link ( what I'm leaning to). I'd want to keep all 3 links the same in regards to length and end size. Than I'd be able to carry 1 link as a spare for them all.

EndlessMtnFab

Don't do that ... you will end up with some screwy numbers (per the calculator) and your handling characteristics will be a bit undersirable.


Ideally, the upper should be longer than the lower by at least 1 - 1.25 inches and be as level as possible.


Study the screen capture in the thread and you'll see what I mean. Download the program and plug in my numbers. Then start fiddling with the link lengths (making them equal) and you'll see what I mean.



The calculator is *not* the final say in design. It just cuts down a lot of the trial & error process. What feels good to you, may feel awful to me. Best suggestion I can give you ... build in as much adjustability as you can.



Joe

4.3L XJ

If you are going to carry a spare link, the bottom one is the one to carry. The top link on a three link is well protected by the frame rails etc. It shouldn't be an issue

nick_n_ii

Ya, I have the calculators. A few of them.

I'll have to play with the numbers.

It is a DD and right now it's just the planning stage..

Only time frame is by late spring.