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Suspension links and all that great stuff...(posted also in ORD forum)

BigOrange90Jimmy

BigOrange90Jimmy

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I'm putting coilovers on my Yota and I've been having some trouble brainstorming what kind and how many links I want to run on it and in what fashion.

I'm using the stock boxed Toyota frame, and fullsize axles and I'm wanting to run coilovers. Right now, I can add more bracing to the frame if needed, because it's just a bare frame. The metal thickness is 3/32, so I'm guessing I will be welding maybe 1/8" steel to the bottom and sides of the chassis to give it some more beef. Think this will be overkill or should I use a thinner gauge metal?

Now for the suspension talk. I'm wanting to be able to kick this pig down the highway occasionally, so I need it to be stable. I figure come here because I have no experience building anything like this, nor does anyone else around me. Sure, there are plenty of race car shops, but they don't think with gobs of flex in mind, so they're a lost cause. All I can do is weld, so we're good in that department!

Right now, I'm pretty much set on either a 16" King coilover, or a 16" or 18" Sway-A-Way. My point of view is, it costs the same, why not get the most amount of travel possible.

I was thinking of running what I guess the "Pro's" would call a 3 link setup. I was going to run two links to the axle to locate them using a K link on each arm. I've seen it used on a Grand Cherokee and liked the idea of having the ground clearance of only 2 arms, but the axlewrap control of 4. With this setup, I would be running a panhard bar. Here's a ROUGH sketch of what I'm thinking of:
K link

What I've also seen is a "U" type 4 link (kinda). The sketch will explain better than my typing. U link

The next one is a typical 4 link with the top links meeting in the middle. V link

Or ya'll can suggest one. I don't really care. The drawing board is blank, and I'm open to any suggestions. I've been looking at pictures of the ORD K5 suspension and I'm still trying to figure out what I need to do to work it out. Well help me out if you can. If not, I understand. Thanks guys!
 
I don't know much about links, but my buggy will probably be linked soon, at least in the rear. My current preference (it changes over time) is for a wristed radius arm type setup with track bar in the front (if I do the front). And either a 3 link or maybe even a modified torque tube type thing for the rear (as suggested to me by MJ). Either way, I would recommend you read the "God of Suspension" thread and several others on Pirate. There was also another pretty good thread by TBI<something-or-other> recently.
 
BTW, what you called a "K link" is (sorta) what I call a wristed radius arm. Normally a 3 link has 3 more-or-less parallel links and a track bar. Usually, one link top near center, and two on bottom outside. I've also seen people call it a 3 link with parallel lowers on the outside and a triangulated upper link with the ends spread at the frame and a single joint at the diff. But, that I prefer to call a Wishbone upper...
 
I would suggest you do alot of research on this before you start. A good place to start is Pirate. There are many things to take into consideration when designing the system such as roll steer, anti-squat/dive, etc... I've been researching this stuff for about 2.5 years now and I am just now getting the final design for my willys done. And I'll probably still be making changes to get just a 1/2 of a percent less anti-squat etc. There are also many good books out there on suspension and chassis design. I like Chassis Design by Herb Adams. But most of these are geared torwards on-road cars and such. But the basic design principal is the same. Good Luck!
 
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There are many things to take into consideration when designing the system such as roll steer, anti-squat/dive, etc...

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uh...yeah...what he said. I don't get it, I never will. If it works, it works? /forums/images/graemlins/rotfl.gif Seriously, that stuff gets me lost everytime I even try to read it. I guess all I can do is build it and hope for the best and expect the worst.
 
I would sugest against your U-link, and V-link.

They will allow for straight up and down axle movement (which is good) but will cause alot of bump steer with crossover steering (which I assume you have...if you don't do that first).

I tend to shy away from Radious arms...even more so if they are not wristed.
 
Yeah if your planning on running crossover and not full hydro steering then your best bet for the front is a 3 link with 2 parallel lower links and a single upper link centered. Then a panhard bar that runs parallel and is the same length as your draglink. That way you will almost eliminate bump steer since your axle will travel in an arc as it goes up and down.
 
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but will cause alot of bump steer with crossover steering (which I assume you have...if you don't do that first).


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Hehe, I don't have anything yet, just a bare frame. I had thought about going with a full hydro setup, but I don't know about it on the highway.

I was looking at Stephen's setup on his K5 and I really like how the steering is setup. I can get just about any steering setup to work though, because my frame is so narrow and the axles are so wide. Clearance is not a problem.

I have to address one problem though. I plan on running a diesel in this truck, so that means I will have to have either Hydroboost, or a stand-alone style booster. I don't want to stress the pump too much by having hydro steer and brakes going at the same time.

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I tend to shy away from Radious arms...even more so if they are not wristed.

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Why don't you like them, if ya don't mind me asking? You don't suggest any of these setups. How about hooking a brother up with what you think will work? /forums/images/graemlins/thumb.gif Should I go back and re-think the setups, or what? I'm telling you man, I have no one to help me with this, so whatever you can tell me will be plenty helpful. I've read the multi-page Links thing on Pirate and have the 3D drawings bookmarked, printed, and framed. /forums/images/graemlins/rotfl.gif I just don't understand how they figured out all of these angles and stuff.
 
I like the wristed radius arms in the front when you run a CV shaft. The locked side on the passenger side keeps the pinion pointed correctly. A front 3 link works good with a u-joint shaft since the axle moves (mostly) straight up and down.

As for Stephen's steering, that thing is trick and works well, but simple it aint.
 
Actually, if you design your link system properly you can make it so the pinion points at the t-case no matter where it's at in the travel. My willys suspension is this way.
 
Agreed, it's just easier with the matches I posted. Trying to keep the orientation of the pinion along with anti-dive, minimal flex steer, strength, clearing components that are in the way, etc. just adds to the complexity. JMO, but I match them up that way to make at least one part of the equation fairly simple. Plus, I've seen some fantastic, functional front suspensions using wristed radius arms so I'm not shy of them...

Good luck with your Willys, looking forward to pics. /forums/images/graemlins/laugh.gif
 
I don't like how a with wristed radius arm the axle moves with the side of the axle that has the non-wristed arm. This means that your caster changes in different amounts depending on if you are making a left or right turn. This might be acceptable to some but to me it doesn't sound fun.

If you have a way to pin up the wristed arm for street driving it will act as a sway-bar and eliminate the caster goofiness at the expense of bushings...it will bind horribly if you use heims. With a wrested radius arm the load on the non-wristed arm will take all the torque loads (braking and acceleration) on the axle and because of this must be designed strong enough to not bend (the loads are bending and not axial which makes them weaker).

I think that covers most (but not all) of my reasons for not liking them…aside form the fact that Ford used them.


I would do a 3 link with all 3 links the same length (so you only have to carry one spare) and use a panhard bar to keep the axle from moving side to side. Try and get the 3rd link as close as possible to the center of the truck (you will have to move it off to the side to clear the oil pan). I would angle the lower arms in from wide at the axle in to the frame. With this configuration your roll axis will be the line connecting the middle of your panhard bar to where the 2 lower links intersect. It will also keep the tires from rubbing on the links when you turn. If you play with it you should be able to get it so the roll axis inclines very slightly as the suspension compresses and droops. This will mean that you won’t have problems like oversteer under braking and understeer under acceleration. Your Roll Center (RC) will be fairly high with this setup (depending on where you put your panhard bar) which I think is good on a 4x4. It also allows you to angle the 3rd link however you want (and hence having your IC wherever you want).



If you think it is getting complicated it is!
You should make sure you understand at least a bit, things like Roll Center (RC), Roll Axis, Instant Center (IC), and Anti-Squat/Dive before you start hacking off your leaf springs.

There are some out there (like Camo on Pirate) that think leaf springs are the best front suspension out there for a trail rig. There are many added variables to contend with when “linking up the front” than the rear. If your are going to go through with this you need to know why you are going to do it and have an idea of what you want to achieve. Personally I would suggest you link the rear and leave the front for later…

Lastly:
There is no one "right" way to link up a truck (but many wrong ways!). You have to figure out what you are willing to compromise and what you aren’t.
 
I would go with a 4 link personally. I have never built one but it seems to make the most sense to me. The straight forwardness(is that word???) seems appealing to me. I have however built a remote control monster truck that made about 80 degrees artic... /forums/images/graemlins/shocked.gif
 
If I went with the wristed setup, both sides would be like that, not just one. I like the 3 link with the panhard bar idea. It seems to be the simplest to figure out and build. I don't mind running a panhard bar, and I know how to set it up for the most part. Where can I find this book on suspensions that was mentioned earlier?
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before you start hacking off your leaf springs.

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Too late. The day I got this truck, the sawzall came out and everything that I didn't want on it, I removed. All that's left on the frame now is the cab mounts.

I'm in a mood for coilovers. I'm wanting to break something out that this side of the state hasn't seen yet. I don't mind trailering it everywhere, but what's the fun in that.

Right now, I think I'm set on the 3 link. I can swing doing it, as soon as I get that book.
 
3 link is the best choice IMO
although I am leaning to torque tube now although I havent looked at the math to package it
 
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If I went with the wristed setup, both sides would be like that

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You can't have both "wristed" at the same time. The front end would just flop all over the place.

Look at a ford front end. They have non-wristed radius arms. If you were to wrist them that means to put a piviot in the front end of the radius arm. You do this so it will articulate...if you don't the only way for it to articulate is to twist the bushings. What some people do is wrist both sides but they make them both able to be pined so they won't rotate any more. Then you just unpin one side when you are going to take it off road so it will actually flex. You get to deside which side you want to remove...based mostly on which side your driveshaft likes more.
 
Can you explain to me how Stephen's steering works? I have stared at that picture for long periods of time trying to figure out how it works and cant. Thanks
-fLeXy K20
 
The steering box is in the middle of the frame. The pitman arm pushes the first drag link over to the drivers side frame rail and is attached to a pivot arm. Also attached to this arm is the second drag link which goes to the steering arm on the axle. So the box pushes the first draglink which pushes the pivot out which pulls the second draglink out which pulls on the steering arm, and the other way around for steering the other way... Get it? /forums/images/graemlins/rotfl.gif
 
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