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Discussion Starter #1
I've been on this board for a while now, and i've done more reading than I ever would have expected, and I find myself with an aching brain fairly often. I've searched around and read countless posts about 3 links and 4 links and different designs as far as triangulation, and though i've learned a lot I still get confused about roll center, antisquat, etc. especially when comparing multiple designs. I was thinkin it would be good to have one thread that explained in laymans terms exactly what works, and how to set it up. and since this is the PBB i'm definitely talkin for rock crawling.

What I'm lookin for is some simple tech mainly on triangulated 4 links and wishbone style 3 links, since they seem to be the most popular. I dont need all the engineering #s, I just wanna know what works the best, how to set up the links, vertical separation at the frame and axle, horizontal separation, and any ill handling effects from either. Also since some of us still like to drive our rigs to the trail I'd like to know what setup works on a street driven trail rig.

I know there are some awesome minds on this board, and there is already a shitload of suspension tech on here. I'm just hoping these suspension gurus can dumb it down for some of us so maybe we can build our own setup that works without a mechanical engineering degree (i wont have mine for another 4 years or so). Thanks guys.

Dallas
 

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This has been asked for many times. What it always turns into is a pissing contest between folks who like to use big words and acronyms in order to look smart.

It would be nice to lay it down in general terms (as you've requested. on a triangulated 4-link, you want to keep the links a few inches apart which does this. Etc.

Good luck man. Bring on the next pissing contest!

Jack
 

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Discussion Starter #3
thats exactly what i'm talkin about. the big words are makin my head hurt and i'm a fairly intelligent guy :p I'm just lookin for some basic rules on what works and why, in words anyone with a high school education can understand.

Dallas
 

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i hacked all the shit outta the way(gas tank, shock/leaf spring mounts), then setup the 1/4 elip. springs and drew links on actual pics of my truck and posted here. a couple of pointers from guys who have done it before and i ended up with a real nice setup.

you can throw down perfect link lengths, mounting angles, vertical seperations and roll axis points, but whether or not you can actually get it to fit your frame and around your vehicles ancillaries(gas tanks, floorboard, crossmembers, etc)is another, there is no generic setup that we all can use.

like iron bender said, youll end up with soooooo may comments from fawkin morons that dont know shit, youll have to filter through it all. i had to read forever through all the posts to slowly figure out who the hell was a genuine person with some worthy knowledge and who was some jackass pulling his ass inards out and smearing it on the internet....good luck, youll love wheeling without axle wrap and hopping:D
 

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if you really don't want to figure all the stuff out you should just copy somone elses design that works.

I learned most of the suspension terms and shit by reading the milken book and talking with friends, it is not that hard to learn, just hard to remember (if you don't do it everyday)
 

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I to did a bunch of research on this subject only to find out that there is NO perfect setup for all rigs, even if they are all rockcrawlers. Wheelbase, width, height, horsepower, weight, driving style, terrain ect all factor into the design. I think you should start with a tried and true setup, with a resonalble antisquat, a fairly high and level roll center and go from there. Reguardless you will have to make some adjustments after you get out there and see how the rig responds. I think you need a baseline setup that is well thought out and then adjust from there cause there is just to many variables to play with on paper.

Search under my user name for 4 link to get an idea of the thought process that went into my Rear double triangulated 4 link..

Good Luck!
 

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Booger Weldz said:
i hacked all the shit outta the way(gas tank, shock/leaf spring mounts), then setup the 1/4 elip. springs and drew links on actual pics of my truck and posted here. a couple of pointers from guys who have done it before and i ended up with a real nice setup.

you can throw down perfect link lengths, mounting angles, vertical seperations and roll axis points, but whether or not you can actually get it to fit your frame and around your vehicles ancillaries(gas tanks, floorboard, crossmembers, etc)is another, there is no generic setup that we all can use.

like iron bender said, youll end up with soooooo may comments from fawkin morons that dont know shit, youll have to filter through it all. i had to read forever through all the posts to slowly figure out who the hell was a genuine person with some worthy knowledge and who was some jackass pulling his ass inards out and smearing it on the internet....good luck, youll love wheeling without axle wrap and hopping:D
:D ok paul youre so smart, just tell me a few things
1. how far is the distance from the top of your axle tube to where the rear of the frame flattens out
2. how long are your lower links,
3. what angle are they at relative to each other and the ground
4. same for upper links
5. did you use f350 springs ( i have a set)
6. can i do this?
i am a moron and just want to basically copy exactly what you have since you already did all of the work:D
7. oh and when will you guys take me thru the con:D
8. do you have any papers, i am all out:D ?
 

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Discussion Starter #8
alright, i think i may have stated this a bit wrong. I'm not actually building a 3 or 4 link for my rig. I'm quite happy with my leafs. However eventually I will be doin a link setup on my next project rig (sammi) and probably build a buggy as well. I really just started this thread to see if we could get some good basic tech. Just some general rules to follow to start to design a suspension that works. i know there is no one size fits all solution, i'm just lookin to see if we can agree on what works for most people as far as link angles, separation, length, etc.

I said triangulated 4 link and wishbone 3 just because they seem to be really popular and i'd like to see some tech for the garage mechanics. I'm all about the little guy :flipoff2:

Dallas
 

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Why do you need to search and caulculate 4 links so much? I have built two and i did it just by looking at the milkins book and learning the princibles and then appling them to the rear of my jeep and a freinds ramcharger and the results are bitchin. NO rear steer a little to much unpredicted off camber body roll but nothing some leaves up front cant take care of. 83% antisquate and ample articulation. JUST BUILT IT! offroad BB's are the root of procrastination for building 4x4's.
 

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fullsize80cherokee said:
Why do you need to search and caulculate 4 links so much? I have built two... a little to much unpredicted off camber body roll.
You critisize people for too much time spent designing, and then explain exactly why they do it. Way to contradict yourself. :flipoff2:
 

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I think the closest thing you'll get to a "Links for Dummies" is the article in the July issue or Petersens 4wheel, but that is still far from perfect.

FWIW, the basic suggestions everyone seems to repeat over and over again is
- try to make your links parallel when veiwed from the side
- make them as long as you reasonably can
- make them as flat as you reasonably can
- make the roll axis as high as you reasonably can
- vertical separation should be 6" or more. More especially for more horsepower and/or bigger tires.
- make the triangulated portion 40 degrees or more for decent lateral control.


And like others have said, there is NO perfect setup, nor is it very easy for anyone to give you a specific range of things to shoot for... :(

My suggestion is just to do a LOT of searching and reading and drawing and thinking, and re-reading, and thinking some more.

Like Booger said though, there are lots of people spouting off that don't know what they're talking about, but after a while you start to figure out who knows their shit and who doesn't.
 

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ErikB said:
- try to make your links parallel when veiwed from the side
IGNORE THIS!

Is that strongly worded enough?
There are a handful of people on here who really perk up my ears when they talk link design (PIG, Gordon, and a couple others) and I've yet to hear them recommend parallel upper and lower links.

A lot of people who have read enough to be dangerous (myself included here) will recommend parallel links, IMO because you can set them up without extensive trial and error, math, or test-fitting. However, I have yet to hear a convincing explanation for an infinite instant-center (what parallel links give you) being a good setup.

Somebody prove me wrong, or STOP POSTING THIS. Please.
 

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This is how the pissing match gets started.

Tntoy - instead of blurting out "ignore this" and then go on to spew some crap about nothing and then beat your chest and say that "Somebody prove me wrong, or STOP POSTING THIS. Please." What you should do is simply explain why keeping the links parallel is not the best way to go. If you carnt do that then just keep you mouth shut and let the good tech flow.

Now I agree with what ErikB has said. I do think that for sombody that doesent necessarily understand all the intricate ins and outs of anti squat, roll axis blah blah blah that this is the best way to try and build it.

So to say it again (cut and paste job here)-

- try to make your links parallel when veiwed from the side
- make them as long as you reasonably can
- make them as flat as you reasonably can
- make the roll axis as high as you reasonably can
- vertical separation should be 6" or more. More especially for more horsepower and/or bigger tires.
- make the triangulated portion 40 degrees or more for decent lateral control.

If you do this then you will end up with as little anti squat as possible and with the least body roll as possible and as the suspension cycles things will remain as stable as possible. Now IMHO this is the best place to start when building a link suspension - something that gets the power to the ground in the most stable way possible ..... meaning that it has the least possible chance of starting to hop on throttling climbs or walking a wheel undernieth on slow articulating climbs and it has the least chance of rolling you over on the off camber climbs.

If you do this you will have a linked setup that will be the most nicely behaved setup that you can produce - you will break less rear axles and diffs and you will roll over and flip over backwards the least.

Now if you find that your rear suspension doesent really hook up and bite into the rocks on the throttling climbs and it doesent hop at all then you can start to experiment with more anti squat. Easest way to do this is to lower the chassis mount of the upper links. If you are smart you will build this option into your links when you first build it so that you can play with it later. But IMO you are best to start with the least amount of antisquat as possible and then work your way towards more antisquat. Most people build links because their rigs hop and buck and generally behave really badly when the power comes on so IMO you are best to start with the other extreme.

In the majority of cases IMO you will still end up with more antisquat than a totally 100% neutrally handling rig. Just by running a lifted rig with big tyres will generally give more then enough anti squat even if you try to totally minimise it.

As a side note I just got a copy of the super crawl video from last year. Now if you watch it carefully you can look at the rigs that hop badly on the climbs, the rigs that hop a little bit and the rigs that dont hop at all. Now it is easy to see that the rigs that dont hop at all run the least amount of antisquat (by looking at the rear link angles) ... the ones that hop a little bit have a bit more antisquat and the ones that hop a lot run a lot of antisquat. Its that simple.

Sam
 

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I have a good rule of thumb for ya ...

Always try and tuck your rear's lower link brackets up and out of the way ... the best suspension in the world won't help you if yer hung up on a low hanging bracket.
And make them tough because they take the brunt of all the climbing forces.
 

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Jaffer said:
I have a good rule of thumb for ya ...

Always try and tuck your rear's lower link brackets up and out of the way ... the best suspension in the world won't help you if yer hung up on a low hanging bracket.
And make them tough because they take the brunt of all the climbing forces.
Agreed, mine are almost totally above the chassis and behind the tires.



Although I must say I have seen many a longarm used as a ramp to help slide the rig up, I am just not sold that it is easier then the tire pulling you up.

Also only the mounting points really matter, having an arm that isn't straight doesn't effect the handling assuming the mounts are in the same location.
 

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OK I take a stab at link for dummies. Most will be like ErikB posted which are good. I'll expound a bit more.

-I would recommend a Tri-4link or 3link wishbone, for the rear. If planning front I would also recommend unless physically impossible due to driveline configuration.

-Place the converging Links on top of the axle with upper tri or wishbone, OR at the lower crossmember for lower links. This will keep your roll center fairly high. You can do both for a double Tri-links.

-Keep the tri links angled as much as the chassis you are building will allow or axle. It hard to go with a hard fast number here because widths of chassis and axles vary so much. Example: my 48" on center widthed chassis isn't going to allow for as much as a regular sized frame.

-Keep the remaining links wide on the axle attachment point. This will allow for more stability. Here again you have to account for the tire throughout their travel and if they steer. Just like leaf spring, you don't want the tires rubbing a lot on the links, so would be OK, but I like none.

-Vertical separation is important to take the torque rotation from the axle under power, and even more important with portal axles. Place the lower link attachment points at the axle so the brackets are not lower than the axle tube. You can go lower but will take away clearance and hang up on stuff. Then place the upper axle mounting position fairly high, again you chassis setup will dictate this a lot (especially in front under the engine). See how much compression you want, what the links will hit and make slightly lower. Once under the rig it will be clear how much, and too much isn't necessarily a good thing.

-After all of the above, you should have the axle mounting placed, or a good idea where they will go, then focus on the chassis. The lowers should be placed in the chassis to be tucked away so you have good clearance and don't get hung up. This would be either frame mounted or cross member mounted. If you have to build lower because of chassis clearance issues build a ramped mount.

-The last set of links to place are the chassis upper, all others you should have a good idea where they go from the above text. Here is where I would build in some adjustment to the suspension. All other points can be solid mount with no adjustment because they take into account other thing for best placement. Make a attachment point with several (3 min) holes that are on the same arc as the link at ride height. You will also see that the body or chassis will dictate the location of this bracket and will probably allow for some positions that have less link separation that at the axle and maybe one parallel. These adjustment holes will allow for some tuning of your anti-squat and IC. They will allow for smaller adjustments than if the lower chassis mount was adjustable.

-Lastly build strong brackets, especially at the chassis and convergence of the tri link or wishbone.

That will give you a good start. This is by no means the be all end oll of building a link suspension I probably left out a ton of stuff. Look at a lot of different suspensions and you will get a good idea. You really have to see what will fit with your chassis and axle, and go from there. Unless your are building a full on tube chassis from the ground up, your configuration will dictate a lot of how the links will end up. This is even the case when building custom chassis, its just easier to move stuff when building from scratch.

Take a look at my site and you can see mu link setup and my adjustment brakets. Oh and Good luck.
 

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aaron t said:

:D ok paul youre so smart, just tell me a few things
1. how far is the distance from the top of your axle tube to where the rear of the frame flattens out
2. how long are your lower links,
3. what angle are they at relative to each other and the ground
4. same for upper links
5. did you use f350 springs ( i have a set)
6. can i do this?
i am a moron and just want to basically copy exactly what you have since you already did all of the work:D
7. oh and when will you guys take me thru the con:D
8. do you have any papers, i am all out:D ?
honestly i dont know dick about link type suspensions, i too am a moron, but i can copy other peoples work like nobodys business:D mine was a conglomeration of desertoys, dustin emmicks and some helpful hints from people here.

1. i dont know i sold the truck
2. 47"
3. see #1
4. 36"
5. no, long side of the f250 (31"), but f350 work great as well
6. yes
7. any weekend you get your sand covered ass up here:flipoff2:
8. no, i use a glass pipe:D
 

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links

i want to thank you guys for the great pics on your site and the info ,i myself am going threw a front linkage set up , when i finally got the links rite i had to deal with the steering of which i have come to a dead stop and wanting to go on the up comeing trip to the dusy trail,i am takeing the links all off and going back to leaf for now , i want my rig to be freeway safe so i have to come up with a safe steering system till then its back to the leafs. my point is that links are great but theres more to it than the links ,its the steering thats the hard part its binds easy unless you have full hydro or have a really complecated bell crank set up, so you guys have to take that into consideration when makeing the choice of what you want to do,as i would,nt feel safe going 65mph relying on power steering hoses,valves,hydrolic pumps etc etc. unless some body can show me a good design thats works well on the trail as on the freeway. your input will be greatly apreciated
 

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OK, no one mentioned this basic point ...
It's generally a good idea with a CV set up to keep the rear's upper links shorter than it's lowers so the pinion's yoke will stay pointing towards the TC's yoke.

Edit:
Though it is (gently- thank you) pointed out below that this geometry does make the pinion yoke point down and away from the TC on full droop it is also true that as the axel rises the pinion will also nose down and remain more oriented towards the TC because the longer arc of the less horizontal bottom arm quickly overtakes the the arc of the shorter top arm.
 
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