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Can you comment on my ideas to redo my links? (with pics)

5K views 37 replies 11 participants last post by  Bigger Valves 
#1 ·
Note: I didn't build my rig and don't meant to put down the builder. He's a friend of mine and I'm *sure* if I built something I'd find room for improvement later on too.

This is the best semi-recent picture of my rig that I could find. (That's my daughter helping me bleed the brakes.) You can see the front and rear lower control arm hangers and imagine how they get hung up on things from time to time. In the rear, I've figured out how to make them longer, move them in and up, and still having good anti-squat characteristics. In the front I could use the forum's opinion.

Current picture:


Proposed change:
The goal is to stretch the wheelbase about 2 1/2" to 106.5". In addition to more wheelbase I'll be able to lower the rig about 2-3" because the upper control arms will then clear the oil pan. (Unrelated: I'll also move the upper air shock mount to go from 3" to 5" of up travel.) Due to clearance issues I can't move my lower control arms just anywhere I want them. I haven't run the numbers but visualizing the instant center and the anti-squat line tells me it will be somewhere around 150%.



It will look a be a better with the rig sitting lower and it will be a joy not to grind that hanger all the time but what do you guys think? Would you take a flatter bottom over front link geometry? I'm under the impression that the front doesn't matter as much because of 1) The winch can control it to some extent 2) Anti-squat only comes into play when you have traction and if things are rough the front tends to be somewhat light anyway.

Thoughts?
 
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#4 ·
If you lower it 2-3" then the whole belly will hit on things only the hangars hit before... food for thought.

150% is crazy high.. ya sure about that #?

I've hit and drug the front hangars on a bunch of things but it's never held me up.. the rear I could see being a totally different story, however.

You just need bigger tires... :flipoff2:
 
#6 · (Edited)
You're right about the belly hitting and the bigger tires. Then end goal is to get 40" comp tires but that will have to wait. As for being sure about the numbers, no I'm not sure. It's just sort of an "electronic back of the envelope calculation". I'm having a hard time measuring it when I'm looking to change pretty much everything (wheelbase, control arm length, chassis height, mount locations, etc.).

Here's a picture that shows some of the relevant points. (Yeah baby, envy my awesome MSPaint skills :flipoff2: ) I see it as about 200% AS if I didn't lower it and so maybe 150% after I do?

My real question was how important are AS numbers in the front? I'm thinking it's not very important because AS only has an impact when you're have a lot of traction and torque and that's less common for the front end.


Furthermore, I looked at Chris's rig because I know he does a lot of extreme stuff and takes the time to dial it in. If you draw the same imaginary 100% AS line through the instant center I think you'll get a really big AS% (200%) for his front links too.
His pic:

My "back of the napkin image":


So at least one person seems to think that getting the control arms out of the way is more important than AS in the front suspension. :D
 
#8 ·
Make sure you have enough separation at the axle and punch the rest into the 4 link calculator.

In my experence you should keep the front under 150% and rear under 100% You can always lengthen, bend and gusset the uppers/lowers.

have you considered a 3 link front or a parrallel 4 link with panhard? Both would eliminate oil pan issues.


http://mysite.verizon.net/triaged/files/3LinkV1.0bBETA.zip

if you don't have excel you can search and find a html version.
 
#9 · (Edited)
My front 3-link is at 60%ish and I love the crap out of it. There's nothing I'd change; it doesn't unload, hop, dive, etc.

Although, all the design work in the world won't help if you're stuck on a rock magnet. So there are compromises to be made. I would get the AS as low as you can without making too much of a mess of the undercarriage.

edit: Here's the layout so you can get an idea of the angles my links sit at to get those numbers:

 
#10 · (Edited)
My front 3-link is at 60%ish and I love the crap out of it.
Loving the crap out of something is creating visual images that I'm having a hard time living with. :laughing:

But now that you say that I think a three link might simplify my crowding issues. I'm going to give that some serious thought while standing in front of my rig. If I had a nickel for every great idea that fizzled after I thought it through while standing next to the buggy I'd be worth at least $1 more by now.

I don't remember it exactly but isn't there some problem with 3 linking a steering axle? What is the counter argument? Is it relevant to trail rigs?
 
#14 ·
I plugged my front end numbers into the 4 link calculator a while back, I'll check at home and see if I have the spreadsheet still. From what I have seen the front suspension is no where near as critical as the rear since you can winch it down for the big climbs which flattens the link angles.

On your link mounts, I'd definately try to tuck the rear ones up and out of the way. The fronts may not be worth it, mine hang down pretty low but they haven't really been an issue.

Edit - that pic of my rig is deceiving, there is a lot more vertical separation at the chassis end than what the sketch shows. I'd guess 7" at the chassis and around 6" at the axle.
 
#17 · (Edited)
Edit - that pic of my rig is deceiving, there is a lot more vertical separation at the chassis end than what the sketch shows. I'd guess 7" at the chassis and around 6" at the axle.
Which gives a really low anti-dive #. I've got 7-3/4" at the axle and 6-3/4" at the frame, and it's at 25%. Haven't had to use the winch cable much at all so far. The front tires climb right up the rocks without extending the suspension first. The front probably isn't as important as the rear, but it matters.. there's been a few threads about it semi-recently, and it's part of what prompted me to shoot for a low AD % in the front.

Sounds like you already made up your mind on what you want to do and that getting the link brackets off the bottom of the frame is most important to you. if you raise up the lowers without raising the uppers, you're gonna gain a bunch of AS/AD. Can you move the uppers as well?
 
#21 ·
As I understand it, you're correct, but only on something where you're carrying your front tires completely in the air.
If they're on the ground at all, they're helping you, and having a better suspension setup that isn't trying to lift the nose of the rig can only help...
 
#22 ·
Yep...I've been extremely happy with how little unloading my front end experiences in climbing.





(yes, I know the trees are sideways...)

Keep in mind that AS/AD% is directly related to weight transfer. All the AS% numbers from the calculator are computed the same way it's been done for drag cars, which is straight-line, level ground. Acceleration produces a weight transfer to the rear, and the amount of weight transfer that goes through the links vs. the springs is basically your AS%. Lower numbers mean the springs resist the transfer, higher numbers mean the links resist the transfer. 100% AS is when the line of the CG goes directly to the tire contact patch so the springs don't see any of it.

When we climb stuff, those numbers go out the window. I've got no idea what my numbers are on anything except level ground. But we've basically gotten enough data here that we can say "something with an AD% of x will generally do _______ when climbing", so it's still a measurement we can use to compare similar rigs on similar terrain.
 
#26 ·
I just did a 4 link on a Ranger, and on the lower links I put the frame side on the side of the frame so nothing hangs down. I used 3" 3/16" wall box tubing for all the mounts.

If you are having a hard time visualizing it, the bolt goes in from the outside of the frame and the nut is on the inside of the framerail.
 
#31 ·
Also more up travel is never going to hurt you.
-you can winch down the front further
-you have more bump travel at speed
-when winched you will have less belly but if you make it smooth it won't matter
I say don't lower the rig, use the winch to lower ur center of gravity and enjoy not being on the bump stops all the time.
Yeah 7 to 8 inches of vertical separation is the shit.
 
#34 ·
so i guess that's a no.. :flipoff2: Will it sit on the sidewalls you think? Cause if not, then you know the vehicle cg is over the tires and therefore your sprung cg must be higher than that..

Start a new thread.. We can have some fun.. I wasn't able to hit some certain numbers with my setup that I wanted, but mainly because of the specs I wouldn't budge on. I'm hoping for a true cabbed truck that will perch on the sidewalls with the supsension locked out. I don't know if it'll happen, but it's a good goal. My anti-dive is higher than I'd like to have it, but to fix it I have to angle my upper link pretty harsh and I don't wanna do that. If I ever finish the damn thing I can have some real fun.
 
#35 · (Edited)
Will it sit on the sidewalls you think? Cause if not, then you know the vehicle cg is over the tires and therefore your sprung cg must be higher than that..
That would only be true if the sidewalls were really squared off instead of starting to round out toward the tread.

BTW, shouldn't you be contributing tech instead of talking to vetteboy? Where are your thoughts about the importance of anti-dive vs. link position for a front axle?

(Also, it's kind of crazy but I can't think of a good reason not to one-link the rear.)
 
#38 ·
Yea, what you're thinking about doing is pretty much all you can do given the constraints of working with the current chassis.

I didn't post any photos of a buggy on the sidewalls. My current build is a tubed out cabbed rig. I'm not sure whose rig you're referring to but I have seen pictures of such on the boards here and it is sweet.

I'm not a big fan of the one link thing. I think it just leaves out all the inherent goodness of multiple link setups along with the adjustability that you do get. I mean they can be made to work, but I like the tried and true setups and their attributes. With the one link it just seems hard to tune out the funny unwanted characteristics that may arise.
 
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