Mid arm setups....

Pro's? Cons?

Discuss....

i want to know as well.

pro - better clearance than long arm,
better ride that short arm.

RJ, did you really just ask this question?? There's this nifty function called a search button. USE IT! This debate has gone on at least 3 times in the past year lasting weeks. Oh that's right, you're not a naxja member, you can't search the old threads. Here's a hint.....JOIN!

Ary

P.S. I don't know how many people besides goatman are running "mid-arm" setups, but he can't seem to say enough good things about his.

vintagespeed just set up one if I am not mistaken:dunno:

offroadman83 said:

vintagespeed just set up one if I am not mistaken:dunno:

Click to expand...

I've seen long arms on the trail and I didn't like the binding and weird problems that the 'radius' arm setup had. Alot of long-arm guys are now running 3 arms vs. the standard 4 proving there was an error in it's design. I like the mid-arm because I get better control arm angles than with drop brackets, less underframe clutter than the drop brackets, and as much flex as I'll be able to use.

When are you going to show us some pics?Id like to see what you came up with,especially the upper link!

Ok, I haven't really organized pics from the buildup cause I'm not really finished yet. Still building steering & misc. stuff like brakes & whatknot. But here's some shots of the build & testing.

Control arm angles & mount profile:

http://www.rockxj.com/images/3link/angles.jpg

I mounted the arms right behind the curve area on the front frame section, still in the thick part of the unibody.

Upper & Lower passenger side mounts:

http://www.rockxj.com/images/3link/both.jpg

(All 3 arms are fixed length with the upper mount having a stock LCA slider & shims for caster adjustment)

Axle mounts (these are now fully boxed in):

http://www.rockxj.com/images/3link/newmounts.jpg

Axle sitting on the ground, note pinion yoke angle and that the d-shaft is not connect and would not be binding even at this massive amount of droop:

http://www.rockxj.com/images/3link/d44_in.jpg

Axle bracket clearance + 13" at the diff w/ZERO psi in 38.5" tires:

http://www.rockxj.com/images/3link/13_inches.jpg

Angles at ride height (during testing):

http://www.rockxj.com/images/3link/rideheight.jpg

And what it looks like today (essentially):

http://www.rockxj.com/images/3link/imag0031.jpg

So there you have it. I would do it exactly the same again, except I raise the TB up above the axle to make clearance for the ram-assist............instead of having to cut off that bitchin' mount.

looks great...bout maxed out your clearance on the garage it looks like =)

how did you attach the lower mounts to the frame? From the angle I couldn't see if they were just welded. I thought about doing it that way, but was afraid of the integrity of the weld there without the mount wrapping around the sides of the "frame" (for lack of a better term).

Yes, they're welded to the 'frame', I made them longer than the stock LCA mounts and wider to try and get as much weld surface as possible. The unibody actually takes a weld really nice in the thick areas, and I doubt they'll go anywhere.

so how long are your arms now? typical lifted XJ arms are in the 16-17 inch range, longarms are typically in the 32-36 inch range, so how long are yours?

man that is some sweet work vintage!

im looking forward to seeing some completed flex shots of that beast!

Yeah, I like mid-arms, or just longer short arms. The issue to me is the angle of the arms, not the length, so the mounting position is the real issue. The compromise, or balance, is between arm angle, arm length, and ground clearance. I have a thing about ground clearance......basically, I won't do any mod that decreases ground clearance. By the time you set up a long arm to not significantly decrease ground clearance, you have increased the angles and removed some of the benefit of the long arms. If you draw out a couple of scenarios on the garage floor in chalk, drawing the arm positions from stuff to full droop, with the axle movement in an arc, it's very dramatic to see what setup will produce the best combination of arm angles and ground clearance.

With a mid-arm (sort of, longer short arm really), you can position the arms for good angles, and keep the mounts both forward and high enough for good ground clearance. The only negative I see to this is that you have to make everything yourself. So, if you aren't able to design and fabricate yourself, you may be better off with drop brackets or a long arm kit (ouch!). The biggest problem with long arm kits is that the LCA frame mounts are below the frame, and way back.......talk about killing break over angle. Some of the guys who have made their own long arms have moved the mounts higher up, inside the frame rails, which is much better. Drop brackets work very well, but you have to live with the 4" lower frame mount. That can be a problem, but not nearly as bad as long arm mounts under the frame rails further back.

I think the focus should be on ground clearance because, in the big rocks, getting hung up stops you more often than a lack of traction.

Here's a link to pics of mine, the first few pics are of my old D30, the D44 pics start in the second row.
http://fototime.com/inv/DFCDB9A8BDAF591

The LCA's are 19.5", and the UCA is 17.5". The mounting position on the axle is just as important as the position on the frame.

I agree with not wanting to lose any clearance.Thats why I mounted mine high and inboard.Since I used a stock "sized" crossmember I didnt lose anything there.At the intersection of where my old lca mounts used to be I had to cut part of them away before I could put the new ones on,so I lost about 1" there!

completed long arm pics

mad maXJ said:

so how long are your arms now? typical lifted XJ arms are in the 16-17 inch range, longarms are typically in the 32-36 inch range, so how long are yours?

Click to expand...

I'll have to measure them again, but I believe they're 24-25", double JJ's, 1.5" x .288 DOM.

proving there was an error in it's design.

Click to expand...

Hmmm.......someone forgot to send me the memo.....mine seem to be going strong after almost 3 years.

CRASH

Ary'01XJ said:

RJ, did you really just ask this question?? There's this nifty function called a search button. USE IT! This debate has gone on at least 3 times in the past year lasting weeks. Oh that's right, you're not a naxja member, you can't search the old threads. Here's a hint.....JOIN!

Ary

P.S. I don't know how many people besides goatman are running "mid-arm" setups, but he can't seem to say enough good things about his.

Click to expand...

Hmmm...Did Ary just give me a load of crap about a simple question?

Feeling a lil ballsy because you actually wheeled last weekend?


Goatman, the longer short arm setup is actually what I'm looking at doing...The fab part is no problem as I have an Ace in the hole fabricator located up the street who like Guinness about as much as me....I also get my RE stuff at Cost (so did Ary.... :flip, so getting some Superflex joints and fabbing the arms shouldn't be a huge issue.

I'm curious about the ratio in length between the Short ams (say RE Fixed at 16.25 for the lowers) and the new Arms...should I add X% to the RE and then the same percentage to the Uppers...Know what I'm saying. It seems like a really simple mod that would help the ride and flex...

Thanks guys.

TOZOVR said:

Hmmm...Did Ary just give me a load of crap about a simple question?

Feeling a lil ballsy because you actually wheeled last weekend?


Goatman, the longer short arm setup is actually what I'm looking at doing...The fab part is no problem as I have an Ace in the hole fabricator located up the street who like Guinness about as much as me....I also get my RE stuff at Cost (so did Ary.... :flip, so getting some Superflex joints and fabbing the arms shouldn't be a huge issue.

I'm curious about the ratio in length between the Short ams (say RE Fixed at 16.25 for the lowers) and the new Arms...should I add X% to the RE and then the same percentage to the Uppers...Know what I'm saying. It seems like a really simple mod that would help the ride and flex...

Thanks guys.

Click to expand...

As far as figuring out the lenght of your new LCA's, first figure out where your going to mount them, then measure the distance from the frame point to the axle point. Keeping in mind you want a 101" wheel base. Think of the LCA's establishing the WB and the UCA's adjusting the Caster.

CRASH said:

Hmmm.......someone forgot to send me the memo.....mine seem to be going strong after almost 3 years.

CRASH

Click to expand...

The early Bronco guys know about that radius arm bind. Someone just came out with a articulating axle for them Fords.

Bind is your friend. I'll take my bind over the gimmicky, unrestricted articulation of wristed radius arms and the like, any day.

Limit the front axle a bit, and watch the rear axle come alive!

CRASH

CRASH said:

Bind is your friend. I'll take my bind over the gimmicky, unrestricted articulation of wristed radius arms and the like, any day.

Limit the front axle a bit, and watch the rear axle come alive!

CRASH

Click to expand...

Call me silly, but I disagree. Bind is what happens right before breakage and I'd rather flex my components freely than push them to their limit & hope for the best.

Also, if you map out the suspension arc of a radius arm (basically a 2 link) front suspension you'll see a ridiculous amount of caster change throughout the axle's range of motion. What I did with mine was to make the axle mounts (upper & lower) exactly twice as far apart as the frame mounts (upper & lower). If you map this out you'll see a very mild, by comparison, caster change through the suspension arc.

I can't take all the credit for putting this together Greg Gavel (C-Rok) and of course the Goatman helped keep me on track with the design & logic behind the layout. Without their advice I would've had lots of trial and error.