Antiwrap install - JeepForum.com
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post #1 of 17 Old 09-29-2020, 04:55 PM Thread Starter
V8FUN
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Antiwrap install

Got my Ruff Stuff anti-wrap kit today. I called and talked to them about the install, and the jist of it was lower bar parallel with driveline, upper bar parallel with frame. That determines clocking of brackets on axle tubes. The plan is to put the mini shackle on the skid plate. Any reason not to for a mostly street driven rig?

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post #2 of 17 Old 09-29-2020, 04:58 PM
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Are you talking the stock skid plate? If so I wouldn’t mount to that. Too flimsy. That bar sees an awful lot of force on it. For mine I added a DOM crossmember from frame rail to frame rail and mounted the shackle to that. Also used that same bar for the tail support for the Atlas 4 speed.



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post #3 of 17 Old 09-29-2020, 05:15 PM
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I think getting the upper bar level with the frame is going to be tough on a Jeep with more than a few inch lift. That said, I don't think it matters whether the upper bar or lower bar is the shorter one but I'd personally shoot to have the shorter bar at least 75% of the length of the longer one. I would recommend that everything gets welded really well. I made my own and used 1/8" tabs to attach the two bars together... ripped those babies right off because my welds sucked and I didn't realize the amount of load going through that.


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post #4 of 17 Old 09-29-2020, 05:57 PM Thread Starter
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Yeah, I was talking the stock skid plate. I may do some tacks, but I got a guy for welding. Plus the tubing needs notched and all that and he's the one with the tools and know how. If I need to come up with a crossmember too, I guess I need to do some more research.
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post #5 of 17 Old 09-29-2020, 06:47 PM
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Yeah I wouldn’t do the stock skid by itself. I think I’ve seen a few people over the years weld a chunk of square tube to the skid plate to beef it up a bit though. So that could be an option if you reinforce it.

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post #6 of 17 Old 09-29-2020, 07:05 PM
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I did go to the stock plate originally. It did crack it. If I remember right we reinforced it and it did work.
When I stretched the wheel base I added a bar.

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post #7 of 17 Old 09-30-2020, 12:48 PM Thread Starter
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I found a few install threads where they attached to the skid, and thats no doubt where the idea came from. I think reinforcing the skid and going that route is how I'll do mine. With a little luck, should have it done by tomorrow.
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post #8 of 17 Old 09-30-2020, 02:40 PM
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Quote:
Originally Posted by Waternut View Post
I think getting the upper bar level with the frame is going to be tough on a Jeep with more than a few inch lift.
Parallel , not level.

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post #9 of 17 Old 09-30-2020, 08:05 PM
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Getting the upper bar parallel to the frame is more important IMHO than the lower matching the driveline angle. Not the best pic, but it's what I have handy.

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If you well the mount to the stock skid it will rip out (even gusseted). I ended up cutting a section of the rolled edge out and welding in a piece of 1x2 tubing then re-enforcing that with some large angle. No problems since then.


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post #10 of 17 Old 10-01-2020, 04:06 AM
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Parallel upper doesn't matter. The two members are welded together. They will act like one member with the average of the two them as far as the suspension characteristics they give. If they were separate it would be another story The best thing you can do is try to keep it as long and frame side mounting point as low as possible. Its very difficult to do that in a Jeep. The longer and the lower (frame side) you get it. The less antisquat it will put on your rear axle. The more you reduce antisquat the less it will want to wheel hop when you are climbing something. One way to to help lower the frame side is run the shackle upside down where it is in compression and not tension.

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post #11 of 17 Old 10-01-2020, 08:33 AM
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I have a Barnes 2 inch drop skid. Its Quarter Inch plate. They are on Amazon with free shipping for $200 even. You could get one of those and you can weld to it. Thats what I am gonna do when I go SOA hopefully this spring
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post #12 of 17 Old 10-01-2020, 10:37 AM
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Quote:
Originally Posted by 87TPIYJ View Post
Parallel upper doesn't matter. The two members are welded together. They will act like one member with the average of the two them as far as the suspension characteristics they give. If they were separate it would be another story The best thing you can do is try to keep it as long and frame side mounting point as low as possible. Its very difficult to do that in a Jeep. The longer and the lower (frame side) you get it. The less antisquat it will put on your rear axle. The more you reduce antisquat the less it will want to wheel hop when you are climbing something. One way to to help lower the frame side is run the shackle upside down where it is in compression and not tension.
Well since there seems to be some debate over this, I popped open the 4 link calculator that I've been using for my 4 link build. I mean technically this isn't really any different in concept than a parallel 4 link but it's more closely related to a radius arm. Regardless, I think the 4 link calculator can mimic what we're trying to achieve here and can shed some light on the situation.

Here's what I found. You could run your upper bar parallel to the frame or parallel to the ground and it doesn't make a lick of difference in terms of anti-squat or the forces seen on the attach points. I simulated a 30" lower main bar and a 26" upper bar but a 30" and 15" bar doesn't make much of a difference. I then attached them at 20" from the ground in the first scenario and 27" from the ground in the second. With both scenarios, you're already running around 200% anti-squat which is crazy high so 190% or 210% probably isn't going to make a noticeable difference. It barely even changes how the pinion reacts under significant axle droop (roughly 1.5° difference). How you mount the axle bracket doesn't really change anti-squat or pinion angle either. So in conclusion, run your bars how you want and mount the upper frame side where it's most out of the way, most convenient, and forget about it.

However, the one thing that does make a difference is how you mount the axle bracket. It doesn't change anti-squat or the pinion angle at droop but it can have a huge effect on the forces going through the anti-wrap bar. If your axle bracket is straight up and down with 8" of vertical separation, the loads will be nearly half that of the same setup where the bracket is rolled back at about a 45 degree angle and there is only 4" of vertical separation. Basically your upper bar is in tension and your lower bar is in compression under acceleration. The big difference is that the high vertical separation is pulling 20k lbs and pushing 30k under extreme load but if you rotate the axle bracket back 45 degrees the same acceleration loads are now pulling 50k lbs and pushing 55k lbs.


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post #13 of 17 Old 10-01-2020, 10:51 AM
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Link calculator doesn’t work for an anti wrap bar. It is essentially a radius arm. You are trying to run calculations on something with 1 pivot point with a calculator designed around 4 pivot points. It’s not apples to apples. Draw it on a piece of paper and make a force diagram you will see why it length of the bar and angle of the bar affects force applied to the axle and the direction of it.

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post #14 of 17 Old 10-01-2020, 04:14 PM
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I'd argue that it's still 4 pivot points since the shackle is another pivot point that effectively changes things back closer to the way a 4 link works rather than a true 3 point radius arm. However, I'll bow out of this one because I don't really know the math behind how it works and since I'm linked front and rear, it's irrelevant to me now. If a reputable manufacturer tells you how to install it, I'd go with what they say. If they don't....who knows.


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post #15 of 17 Old 10-01-2020, 04:31 PM
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This can help explain it. Basically your instant center is fixed at the pivot point.

https://www.dragstuff.com/techarticl...Baselines.html

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