3 link rear

[Israel]

This is actually regarding my ZJ, but I've found it much easier to get help without drama on than anywhere else so I'm posting it here. Plus, it would be beneficial for anyone considering linking the rear of their XJ.

What I would like to do is build some long arms for the rear of the ZJ. A triangulated long arm looks to be pretty tricky to pull off and have a full exhaust back there. I’ve mostly seen kits that require chopping the tailpipe off immediately after the muffler and welding on a turndown. I’ve heard a lot of good about 3 link + panhard front suspensions, but can’t seem to find a whole lot about doing it in the rear except for Richard’s XJ buggy. I would put the single upper on the drivers side so it would be opposite the muffler. The trackbar/panhard would connect to the frame on the passenger side and to the axle on the driver’s side.

Does this sound like something that would be stable? I’ve heard a lot about the 4 link calculator, but I have yet to find anything about a 3 link calculator program.

Any thoughts?

 

[Weasel]

there is a 3 link number cruncher as well.

 

[IntrepidXJ]

3-link calc: http://mysite.verizon.net/triaged/files/3LinkV1.0bBETA.zip

 

[Israel]

3-link calc: http://mysite.verizon.net/triaged/files/3LinkV1.0bBETA.zip

Thanks for the link. That will give me something to plan better with. BTW, is there any particular reason the 3 link rears aren't as common as the triangulated 4 links?

 

[Matt S.]

Thanks for the link. That will give me something to plan better with. BTW, is there any particular reason the 3 link rears aren't as common as the triangulated 4 links?

I think most of it has to do with the bling factor. Most comp buggies are going to the 3 links front and rear because of the ability to change roll center so easily. They are also easier to fit in tight spaces.

Good luck!

 

[Weasel]

There is a difference from a 3 link or a panhard setup.

 

[TNT]

A true 3 link uses one link to locate/center the axle.

There are alot of 3 links being built that use a panhard bar to locate the axle instead.

The panhard bar can then be used to adjust roll center.

Link to vender that built the following set-up

http://www.trail-gear.com/trail-link.html

 

[TNT]

 

[Israel]

A true 3 link uses one link to locate/center the axle.

Isn't that a wishbone suspension, or am I thinking of something else?

The pictures you posted are exactly what I want to do, but packaged in a full-body ZJ. But the third link will be on the drivers side as shown.

 

[Goatman]

There is a difference from a 3 link or a panhard setup.

Sorry....no there isn't. Technically, there is no such thing as a triangulated 3 link, it is simply a 4 link with two of the arms meeting each other at the attachement point......still 4 links, and it acts like a 4 link. A 3 link has a single arm on the top to control axle torque, so there is no triangulation and a panhard bar is required. In race car chassis books, they count the number of fore and aft facing links, they don't count panhard bars.

 

[Goatman]

I think the major issue you'll have to deal with is getting a good position and length to the track bar. The coils will be in the way, so you'll have to go behind them and still clear the gas tank. The best setup will be with the track bar as long and as level as you can make it. I wouldn't worry about any ideal length for the track bar, just make it as long and level as you can and go with it. Also, the track bar height determines your roll center height on a 3 link, so higher is better for trail stability. Unfortunately, higher also decreases handling predictability going fast on the street, but unless you're a race car driver you'll probably never notice. Race cars go with a low roll center for better feel, and control stability with spring and shock rates and sway bars. Since you're fitting the suspesnion under the ZJ, just go as high as you have room for, and you'll be fine.

BTW, did you notice that the 3 link calculator includes a panhard bar?

 

[vetteboy]

I think the major issue you'll have to deal with is getting a good position and length to the track bar. The coils will be in the way, so you'll have to go behind them and still clear the gas tank.

Remember though that the rear suspension in a ZJ already has a panhard in place, with the same orientation as what he's describing. It shouldn't be too difficult to play with the axle-side mount to get it flatter at a greater lift height.

What rear axle are you using for this? You'd probably want to truss it and/or weld the tubes to the center to help distribute the torque loads a little better.

 

[XJ_ranger]

A true 3 link uses one link to locate/center the axle.

There are alot of 3 links being built that use a panhard bar to locate the axle instead.

The panhard bar can then be used to adjust roll center.

Link to vender that built the following set-up

http://www.trail-gear.com/trail-link.html

holy terrible frame side panhard bar mount design!

 

[Weasel]

Sorry....no there isn't. Technically, there is no such thing as a triangulated 3 link, it is simply a 4 link with two of the arms meeting each other at the attachement point......still 4 links, and it acts like a 4 link. A 3 link has a single arm on the top to control axle torque, so there is no triangulation and a panhard bar is required. In race car chassis books, they count the number of fore and aft facing links, they don't count panhard bars.

A wishbone with a center single link, and then two seperate lower links is a three link. I guess it doesn't really matter but in the books I have you only count the links opposing lateral motion and a joined upper link is a three link.

 

[Israel]

I think the major issue you'll have to deal with is getting a good position and length to the track bar. The coils will be in the way, so you'll have to go behind them and still clear the gas tank. The best setup will be with the track bar as long and as level as you can make it. I wouldn't worry about any ideal length for the track bar, just make it as long and level as you can and go with it. Also, the track bar height determines your roll center height on a 3 link, so higher is better for trail stability. Unfortunately, higher also decreases handling predictability going fast on the street, but unless you're a race car driver you'll probably never notice. Race cars go with a low roll center for better feel, and control stability with spring and shock rates and sway bars. Since you're fitting the suspesnion under the ZJ, just go as high as you have room for, and you'll be fine.

BTW, did you notice that the 3 link calculator includes a panhard bar?

While peppy, the ZJ is no race car and I don't drive it like one, so I'll try and keep the track bar as high as I can. I've taken down some measurements so I can start playing with the 3 link calculator. If you all don't mind, I'll post a screen shot of what I'm getting so you can see if it looks good. Of course I know I'll never hit anything near ideal, especially since I'm restricted in design by the body, but the calculator should give me a good idea of the direction I need to go.

 

[Israel]

What rear axle are you using for this? You'd probably want to truss it and/or weld the tubes to the center to help distribute the torque loads a little better.

I'm planning on an 8.8, welding the tubes to the center and trussing it with a TNT truss. The truss was in the plans more to help with reinforcing the upper CA mount and panhard mount, but should also help with torque from one side of the axle to the other as you mentioned.

 

[Israel]

Well, here's where I'm at so far. I'm thinking of making the upper link bracket on the axle with holes 1" above and below so I can adjust my AS a bit. I'm also not set on the length of the links quite yet. I set my sprung mass CG at 33", but it's just a rough guess for now until I can find a good way to calculate it.

How's it look?

 

[Matt S.]

Where about on the frame rails are you wanting to mount the links? Pics?

 

[Israel]

Where about on the frame rails are you wanting to mount the links? Pics?

I realize it isn't ideal for JV or other rock garden areas, but I'm thinking of mounting the lowers to the bottom of the frame rails and the single upper will be on the inside of the frame rail as high as I can get it without cutting the floor. 90% of my off-roading is moab trails and forest roads, so I'm not too worried about hanging up on the mounts.

What would you like pictures of?

 

[Matt S.]

I realize it isn't ideal for JV or other rock garden areas, but I'm thinking of mounting the lowers to the bottom of the frame rails and the single upper will be on the inside of the frame rail as high as I can get it without cutting the floor. 90% of my off-roading is moab trails and forest roads, so I'm not too worried about hanging up on the mounts.

What would you like pictures of?

Oh! Obviously you have to comprimise on things, and mounting your lower below the frame is probably one of those you will have to make. Not a huge deal. I was just wanting to see what you thought may work for mounting.

I would make you lowers shorter than you are thinking now, maybe around 26-29" and make your upper a little longer. This will really help out keeping your rear pinion in good geometery. Also allowing you to not have such noticable rock grabbers. Make sure you keep as much vertical seperation at the frame as possible as well.

Consider lowering your axle mounts for the lowers down. You should try to get your IC closer to the top of your front tires.

I have nothing to back this up, but if it were me, I would make your AS lower... that way when you load the shit out of it on the trail, you wont have your numbers jump WAY up.