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Unread 10-04-2012, 12:12 PM   #16
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After spending most of my morning reading the pirate thread and this one instead of focusing on school.. Now i wanna go link the rear of my jeep. Thanks for bringin the info over to jeepforum

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Unread 10-04-2012, 12:16 PM   #17
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Another silly question: Could I get my rear suspension set up with my new rear axle and drive it for a while until I save up enough for doing the front (i.e. keep the wife happy by not putting ANOTHER "useless" axle in the shed and have numerous other parts strewn about the house).
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Unread 10-04-2012, 12:40 PM   #18
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Those mounts are from Poly Performance. They mount on the inboard side of the frame rail and angle outward at 10 degrees to give you a little triangulation in the lower links. I use them front and rear with 23" lower arms at all corners. I'll get better pictures of the suspension once I roll it out of the garage.
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Unread 10-04-2012, 02:41 PM   #19
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Quote:
Originally Posted by cycleguy04 View Post
Another silly question: Could I get my rear suspension set up with my new rear axle and drive it for a while until I save up enough for doing the front (i.e. keep the wife happy by not putting ANOTHER "useless" axle in the shed and have numerous other parts strewn about the house).
I sure hope you can, because I'm thinking of doing exactly that.

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Originally Posted by Imped View Post
Those mounts are from Poly Performance. They mount on the inboard side of the frame rail and angle outward at 10 degrees to give you a little triangulation in the lower links. I use them front and rear with 23" lower arms at all corners. I'll get better pictures of the suspension once I roll it out of the garage.
I think those are the same ones I was looking at using. Link. They come in 10- and 0-degree offsets.
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Unread 10-04-2012, 03:26 PM   #20
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Subscribing for the nice tech in this thread.

I've been on the fence about making my own suspension. I've got a Claytons kit already in my possession, but I would like a 3 link front instead of a radius arm setup. Plus I feel like I could come up with a better rear setup as I've read the clayton rear 4 link likes to flex steer and I'd like to get maybe a 108"-109" wheelbase. I definitely got to thinking about it more after the blow up on Dustin's (AllGood_73) build thread since I'm more than likely going to have EOR finish out the rest my build.

My first question...is the top bolt on the transmission what most people use as the guesstimate for COG? I swear I read that somewhere, but I can't remember where...
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Unread 10-04-2012, 03:47 PM   #21
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Originally Posted by Bama_WJ View Post
Subscribing for the nice tech in this thread.

I've been on the fence about making my own suspension. I've got a Claytons kit already in my possession, but I would like a 3 link front instead of a radius arm setup. Plus I feel like I could come up with a better rear setup as I've read the clayton rear 4 link likes to flex steer and I'd like to get maybe a 108"-109" wheelbase. I definitely got to thinking about it more after the blow up on Dustin's (AllGood_73) build thread since I'm more than likely going to have EOR finish out the rest my build.

My first question...is the top bolt on the transmission what most people use as the guesstimate for COG? I swear I read that somewhere, but I can't remember where...
I think that you're more in the "I'm going to build it myself" territory, here. As for estimating the center of gravity...well...don't. I suppose you can use the top tranny bolt as an approximation, but if at all possible you need to get an accurate location for your rig with your load-out. It's not super-difficult to do - especially if you have some instructions - and you'll get better results in your later calculations from having done so. Plus, it's just kind of fun to do.

And what's this "have EOR finish out" your build stuff?
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Unread 10-04-2012, 04:36 PM   #22
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Like I said.....DO NOT obsess over the numbers. You're NEVER going to be better than "a good estimate." Instead of completely relying on the calculator, ie relying on an estimate, truly learn and comprehend what actually gives you the numbers you want. It's much, much simpler than what the calculator makes it look like.

1) Determine how long you want the arms to be--the longer they are, the larger the footprint under the Jeep. I prefer to minimize that. Also, the longer they are, the better chance of them hitting the frame. I prefer to keep that from happening. That's why I kept my arms shorter and tucked under.

2) Determine where you want the axles. This is easy if you aren't moving them, especially up front. Also make sure the axles are close to ride height, as square and centered as you can get them, and pointing up at the correct pinion angle.

3) Tack up an arm, bolt your mounts to the ends, butt the axle mount up against the tube and butt the frame mount up against the frame. If you're happy with it, tack the frame and axle mount on. Now go to the other side, use the same arm and same axle/frame locations and tack them on. There you go, lowers are taken care of. Build the other arm and bolt it in place. Symmetry is important and you've got a good opportunity here to put the mounts in equal positions and make the arms identical in length. Do that.

4) If you're using something like the Poly mounts, your upper frame mount location is already taken care of....one more variable down. Determine the angle of the upper mounts and determine where that line intersects the axle truss. Mark it.

5) Determine how long you want the arm tube to be and tack one up (if unsure, always go a little long). Bolt it up to the frame end and swing it straight back. Build the link tabs if you have to and tack them on. Do the other side.

DO NOT full weld until you're 100% happy that the mounts are symmetrical and placed where you want them. The same goes for the links--you want to have adjustment in both directions. This can be done in ONE day. It takes longer to get rid of the stock mounts than it does to get the new ones positioned.
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Unread 10-04-2012, 06:16 PM   #23
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Now all we need to do is type the word "coilovers" enough times, and a few more people will probably show up.
what? like these? oh - these are mine

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Unread 10-04-2012, 07:17 PM   #24
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Quote:
Originally Posted by Sundowner View Post
I think that you're more in the "I'm going to build it myself" territory, here. As for estimating the center of gravity...well...don't. I suppose you can use the top tranny bolt as an approximation, but if at all possible you need to get an accurate location for your rig with your load-out. It's not super-difficult to do - especially if you have some instructions - and you'll get better results in your later calculations from having done so. Plus, it's just kind of fun to do.

And what's this "have EOR finish out" your build stuff?
Thanks for the COG link. I'll read over it this weekend while I plan on doing some math for a proposed suspension setup.

About the build, I just have a lot of stuff I want to do. And, frankly, its a bit overwhelming for me as I don't have a welder and if I did have a welder, I don't know if I'd trust my novice welds to hold up on the road. Besides the suspension links, I'm looking at getting some kind of cage, cutting up the front end for a "frenched" winch, a smaller radiator, mounting the coilovers, beefing up the unibody and some other stuff.

Quote:
Originally Posted by Imped View Post
Like I said.....DO NOT obsess over the numbers. You're NEVER going to be better than "a good estimate." Instead of completely relying on the calculator, ie relying on an estimate, truly learn and comprehend what actually gives you the numbers you want. It's much, much simpler than what the calculator makes it look like.

1) Determine how long you want the arms to be--the longer they are, the larger the footprint under the Jeep. I prefer to minimize that. Also, the longer they are, the better chance of them hitting the frame. I prefer to keep that from happening. That's why I kept my arms shorter and tucked under.

2) Determine where you want the axles. This is easy if you aren't moving them, especially up front. Also make sure the axles are close to ride height, as square and centered as you can get them, and pointing up at the correct pinion angle.

3) Tack up an arm, bolt your mounts to the ends, butt the axle mount up against the tube and butt the frame mount up against the frame. If you're happy with it, tack the frame and axle mount on. Now go to the other side, use the same arm and same axle/frame locations and tack them on. There you go, lowers are taken care of. Build the other arm and bolt it in place. Symmetry is important and you've got a good opportunity here to put the mounts in equal positions and make the arms identical in length. Do that.

4) If you're using something like the Poly mounts, your upper frame mount location is already taken care of....one more variable down. Determine the angle of the upper mounts and determine where that line intersects the axle truss. Mark it.

5) Determine how long you want the arm tube to be and tack one up (if unsure, always go a little long). Bolt it up to the frame end and swing it straight back. Build the link tabs if you have to and tack them on. Do the other side.

DO NOT full weld until you're 100% happy that the mounts are symmetrical and placed where you want them. The same goes for the links--you want to have adjustment in both directions. This can be done in ONE day. It takes longer to get rid of the stock mounts than it does to get the new ones positioned.
Good stuff. I'm trying to keep from getting to caught up in the numbers, but the engineer in me wants to. That's part of the reason why I figured the top transmission bolt for a COG number would be "good enough".
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Unread 10-04-2012, 08:04 PM   #25
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A four link kit that includes the 8.8 truss, upper JJ control arms and all the needed bracketry would be perfect.

Imped, could you post some pics of your bracket placement on your axles?
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Unread 10-04-2012, 09:10 PM   #26
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Quote:
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Like I said.....DO NOT obsess over the numbers...
That's a really, really well-written synopsis.

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Originally Posted by spyder6 View Post
what? like these? oh - these are mine
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Quote:
Originally Posted by Bama_WJ View Post
Thanks for the COG link. I'll read over it this weekend while I plan on doing some math for a proposed suspension setup.

About the build, I just have a lot of stuff I want to do. And, frankly, its a bit overwhelming for me as I don't have a welder and if I did have a welder, I don't know if I'd trust my novice welds to hold up on the road. Besides the suspension links, I'm looking at getting some kind of cage, cutting up the front end for a "frenched" winch, a smaller radiator, mounting the coilovers, beefing up the unibody and some other stuff.


Good stuff. I'm trying to keep from getting to caught up in the numbers, but the engineer in me wants to. That's part of the reason why I figured the top transmission bolt for a COG number would be "good enough".
Don't be overwhelmed. Let me give you the advice that someone gave me: "Just poke your head under your Jeep and figure out what everything does." Seriously...do that. I know the whole "I don't have a welder" thing is daunting, but welding isn't that hard, bro; if I can do it, then anyone can. It's just a matter of saving pennies and practicing.
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Unread 10-05-2012, 06:30 AM   #27
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Quote:
Originally Posted by cycleguy04 View Post
A four link kit that includes the 8.8 truss, upper JJ control arms and all the needed bracketry would be perfect.

Imped, could you post some pics of your bracket placement on your axles?
Don't have any, I'll have to grab some for you. Think about this....my lower frame brackets are triangulated outward at 10 degrees.....so I make sure the JJ ball is centered, slide the bolt through and swing the arm with axle bracket attached back to the axle. That's where it goes. Replicate it to the other side. You want the brackets to be inline. The same goes for the uppers.

Instead of letting all of these variables intimidate you, let some tell you where to put others....ie, arm length defines bracket placement. Frame bracket placement and angle + arm length defines axle bracket placement. You're just working with triangles here. Basic geometry.
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Unread 10-05-2012, 07:22 AM   #28
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Instead of letting all of these variables intimidate you, let some tell you where to put others....ie, arm length defines bracket placement. Frame bracket placement and angle + arm length defines axle bracket placement. You're just working with triangles here. Basic geometry.
Good advice here. In addition, and even more simple or basic that really got thinking clicking in my head was simply crawling under the rig with your tape measure. He mentioned his arm length is 23". I'm not sure if that's his actual eye-eye length, or link length. My link length is 23", which makes my eye-eye length a bit over 28". I set my tape at 28" then physically placed it where my new imaginary arms would be, one at a time, factory suspension still in place. You know you'll have a triangulated 4 link with uppers converging at center of truss or link bridge up top-put the end of the tape roughly centered above diff and see where the other end fits at the frame. (assuming you're totally scratch with no parts in hand at this time) Do the same for lowers. You know you want them as far out on the axle as you can get and as high as you can get with most ground clearance. Set the tape there and find where the other end wants to be to clear everything.

With that down and understood better what needed to happen, I just started with one arm at a time, cutting off the factory mounts for each arm one at at time. With the factory stuff out of the way, you are ready to fit the new brackets and arm. Fit it, tack it, check it 1000 times to make sure it's exactly where you want it then weld it. Move to next. I did lowers first, then uppers. I set my pinion where I wanted it to be and with the factory arms in place as I worked one arm at at time around it, everything was pretty darn close to where it needed to be once everything was done.

I went for a lot of up travel which required a lot of extra work in the back end with crossmembers, fuel tank location, truss and link height, tub support bars, ended up needing frame notch and box, etc. With this, there is a LOT of cycling and clearance checking to make sure things will clear. Not just the whole axle up and down, but flexed to each side as well. You'll quickly gain a much greater appreciation for how smooth and unrestricted a good 4 link rear is compared to stock.

Best of Luck,

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Unread 10-05-2012, 03:42 PM   #29
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Thanks for the feedback.

A few more questions, although a bit newbish:

1. I assume you go about measuring things with the Jeep at ride height? So I'd have to take the axles out, roll my new axles under and go from there with the Jeep somehow at my ride height (even though I have no idea what that will be)? Anyway to figure this out on stock suspension?

2. How much is to much/not enough triangulation? Some setups I see have lower links at each end of the axle and meeting together at a new cross member behind the transfer case, in essence making a triangle. While the top links go from the frame to the center of the axle housing, making another clearly defined triangle.

On the other hand, I see others like this:
Quote:
Originally Posted by Imped View Post
My rear suspension:
Like you can tell that it would eventually make a triangle (the top of the triangle being at the front axle), but it's not as defined as the previous setup I described earlier in my post. I'm basically talking about the two extremes.

3. A WJ isn't ideal for a LCOG setup (unless I cut the hell out of it). That brings me to the topic of trying to links parallel to the ground. Messing with the calculator, that variable obviously plays a big role in what numbers you get. I have to run a decent amount of lift (6"-7") to fit/stuff 37s, even with a fair amount of fender trimming. That being said, that kind of limits me as far as trying to keep links somewhat parallel to the ground. Any input on this would be appreciated.
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Unread 10-05-2012, 09:20 PM   #30
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1. I assume you go about measuring things with the Jeep at ride height? So I'd have to take the axles out, roll my new axles under and go from there with the Jeep somehow at my ride height (even though I have no idea what that will be)? Anyway to figure this out on stock suspension?
Sure...just take some measurements at your present ride height and then start extrapolating. If you know you're going to run X" tire with Y" springs, then you can take your stock measurements and start figuring from there based on the differences. You don't need to unbolt anything...just get out some graph paper.

Quote:
Originally Posted by Bama_WJ View Post
2. How much is to much/not enough triangulation? Some setups I see have lower links at each end of the axle and meeting together at a new cross member behind the transfer case, in essence making a triangle. While the top links go from the frame to the center of the axle housing, making another clearly defined triangle.
You're describing a double triangulation. "Enough" in my book is "an amount that doesn't allow the axle to move in an undesired/sideways direction" and "an amount that fits comfortably without undue compromise" and also "an amount that yields the numbers I'm looking for with the previous two issues already considered."

Quote:
Originally Posted by Bama_WJ View Post
On the other hand, I see others like this:

Like you can tell that it would eventually make a triangle (the top of the triangle being at the front axle), but it's not as defined as the previous setup I described earlier in my post. I'm basically talking about the two extremes.
That's essentially a single triangulation...or a triangulation and a half. Whatever. Single triangulation - by my understanding - can allow more rear-steer, and double triangulation tends to abate that effect, somewhat. There are also differences in the roll axis. Actually, here's a very basic primer with someone asking the same questions.

I'll go ahead and repeat something that's been said both here and on that linked thread: often, it's more about what you can physically fit in the given space than it is the benefits or drawbacks of either design. Just as Mike mentioned with his desire for uptravel, there are often a LOT of changes that have to be made in order to make a given design work out; take a look under your rig and see what hits and what fits and the available designs will make themselves known. This is one area where I think that playing with the four-link calculator can give you lots of information; you can move link/axle/mount locations around at will and see where the numbers change, based on your under-rig measurements. Coupled with a good understanding of the terms and their meanings, you can learn a lot this way.

Quote:
Originally Posted by Bama_WJ View Post
3. A WJ isn't ideal for a LCOG setup (unless I cut the hell out of it). That brings me to the topic of trying to links parallel to the ground. Messing with the calculator, that variable obviously plays a big role in what numbers you get. I have to run a decent amount of lift (6"-7") to fit/stuff 37s, even with a fair amount of fender trimming. That being said, that kind of limits me as far as trying to keep links somewhat parallel to the ground. Any input on this would be appreciated.
Personally, I'd stop worrying about center of gravity and start thinking on how the rig is expected to perform and how much work it's going to take to get there. I'm not that familiar with the WJ platform, but it seems to me that you're going to be looking at MASSIVE trimming and modification work in order to allow 37's enough room to move...and that would be more on my mind than the relative sex appeal of my rig's center of gravity height.
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