TOTM: Front suspension

[rstrucks]

I highly encourage using the calculator... it is stupid simple to use and having built suspensions with and without the calculator, they definitely come out better when you use it...

Cam, do you have a link to the calculator you are talking about? I'm sure I could Google it and find one but I thought if you had one handy it might be worth sharing.

EDIT - here is the first one that came back on a quick google search - http://mysite.verizon.net/triaged/4l...tml/index.html

[ATL ZJ]

maybe... not familiar with any web based ones... it has been a while since I used it but here's the excel calc I used: http://mysite.verizon.net/triaged/fi...V3.0metric.xls

[ATL ZJ]

oh... also, this is a pretty cool survey of 4 links among a group of rigs that see the same terrain:

http://www.azrockcrawler.com/_images...inksurvey.html

it's about rear suspensions but everything I've been told about building a tri 4 link front suspension is to build it like it's a rear. so it might at least give you guys some baseline numbers to work from, even if the upper links need to be spread out wider on the axle side to clear oil pan, crank pulley, etc

[zjeepin]

very nice! now this is a good totm

[zjeepin]

maybe... not familiar with any web based ones... it has been a while since I used it but here's the excel calc I used: http://mysite.verizon.net/triaged/fi...V3.0metric.xls

wait a minute.. you used a metric calcuator?

[SirFuego]

I think this is the one he meant to post for us Americans who don't use metric calculations:
http://www.pirate4x4.com/forum/showthread.php?t=204893

The first link I believe is the most recent. There is also a link to the 3-link calculator in that thread, too.

I asked this before, but don't recall getting much of a response and this seems as good of a thread as any. When designing a front suspension, is it done completely independent of the rear suspension? Or can you design it to counteract some of the characteristics of the rear suspension?

[zjeepin]

I think this is the one he meant to post for us Americans who don't use metric calculations:
http://www.pirate4x4.com/forum/showthread.php?t=204893

The first link I believe is the most recent. There is also a link to the 3-link calculator in that thread, too.

I asked this before, but don't recall getting much of a response and this seems as good of a thread as any. When designing a front suspension, is it done completely independent of the rear suspension? Or can you design it to counteract some of the characteristics of the rear suspension?

i don't know about the two counteracting each other but you do want the same properties as far as antisquat, instant center in the front as you do a rear.. like cam said a few posts up..

[downtowncb]

I asked this before, but don't recall getting much of a response and this seems as good of a thread as any. When designing a front suspension, is it done completely independent of the rear suspension? Or can you design it to counteract some of the characteristics of the rear suspension?

I don't know about all the intricacies of the link geometries in relation to each other but I know as far as spring rates go you want the rear to be about 10-20% stiffer relative to the wheelbase. This is so the rear can react as fast as the front is when driving at speed and not create pitching.

[ZJ TINS]

Ok having read so far, why is the 4 link always better than the radius arm? For example, for my 95% DD 5% offroad with 4 " of lift, is the 4 link really going to do much more than a radius arm? I mention this due to the cost difference. Is it really worth the money and if so why?

As for caster, by getting adjustable arm's then I can point the axle to any angle I want in it (within reason).

With rubber on the axle side and johnny joint on the frame, for 4" of lift I really do not see that binding, the arc or angle is not great enough. I will double check this later when I get under the ZJ and force it to full compression on one side and droop on the other see what happens. Plus I plan on adding the center strap with 1" of play per Cody.

[IndyZJ]

With a properly designed 3 or 4 link, you can get much better (lower number) anti-squat/ dive than with radius arms. Dual radius arms also bind no matter what height or travel you run by their nature. If there wasn't any give in the joints or bushings, a radius arm suspension would not articulate at all.

Side note: On street rods that run solid front axles with radius arms with rod ends/ clevises, the flex actually comes from a forged axle beam. Guys who run radius arms on tube axles end up braking something.

With only 4" of lift, the arms would be relatively flat and you probably wouldn't notice the downsides of radius arms on a rig that sees little trail time. Wearing bushings out usually happens when you spend a lot of time articulating the front end - on the street, it shoudn't be an issue. Throw in the center limit strap(s) and you shouldn't have a problem with the front end trying to unload from higher anti-squat/dive on climbs.

[ZJ TINS]

Ok so I just measured my ZJ bolt to bolt distance from the motor mounts and it is 24".

So this means from the center of the axle to the motor mount bolt is just under 18" inches for my lift. Given an 1 1/2" tab height (to the hole center or maybe a 2 1/2" tab total height) and that is just under 14 " so according to Cody that means I order 15" straps and triangulate off that. Thats about 1.2" of slack which I can adjust via tab hole height.

[ZJ TINS]

FYI 16" (a little longer i thought) quad thick straps for a pair are $30 shipped to my house. nice!


straps

[ZJ TINS]

ON the anti squat, what is the bad results i.e., how does the vehicle behave with poor anti squat? also what numbers are minimum (below the vehicle is not safe or some other descriptive term) and good (neutral or does not behave any different even thought anti squat number can get better). Did alot of searching and i still do not get a feel for what it means (other than low is good high is bad) .

[IndyZJ]

In my experience, over 100% anti-squat means jacking under load, where lower than 100% will squat. For our applications, you generally don't want your suspension to "jack" under load, especially in a climb. In extreme cases, too much antisquat will literally try to drive the axle under the vehicle. That's the case with my YJ's last suspension - the procrap coil conversion my dad put on when it was cool about a decade ago (the geometry is TERRIBLE). Most coil-sprung Jeeps lifted high on short arms do the same thing.

As has been said, a center limit strap will not allow this to happen, at least not further than the strap will stretch.

edit: With radius arms, the geometry basically is what it is. I'd just make the arms as close to horizontal as possible without killing ground clearance. A center limit strap will go a long way to cover up the high antisquat that tends to come with them.

[AgitatedPancake]

One of my videos perfectly captures nasty antisquat driving my rear axle down and forward. That actually brings up another point, this video also shows how a single triangulated rear 4-link rear steers massively and wants to drive the rear axle up under the jeep.

So heres the link: http://www.youtube.com/watch?v=9G1VBnguT9k

Look at the segment starting at 2:10 when I lose my coil. Thats a pretty severe uphill, so most the weight of the jeep is on the rear end. The rear axle pushes way away from the body and pushes the jeep away from the rock surface. At the same time I'm lifting a front tire without maxing out it's shock, which is showing the binding and unloading on a radius arm. I'd bet that front axle would have tried harder to stick to the ground with a 3 link, not so ready to lift a tire on a climb.

Then at like 3:50 I'm trying to stop my jeep from rolling, but the suspension keeps binding up and pinching, pushing the body up into the air. This part is just really good for actually watching the rear end steer and move as the suspension articulate, because it goes from full bump to full stuff in a split second.

[ZJ TINS]

FYI I looked at the the link calculator and found the most critical dimension by far to get the anitsquat down is the height difference from the top arm to bottom arm on the frame end. Put both underneath the belly and that is hard to do. I am kinda wondering if this is being overthought since most of the kits out there (good ones) use radius arms up front.

[ATL ZJ]

FYI I looked at the the link calculator and found the most critical dimension by far to get the anitsquat down is the height difference from the top arm to bottom arm on the frame end. Put both underneath the belly and that is hard to do. I am kinda wondering if this is being overthought since most of the kits out there (good ones) use radius arms up front.

keep playing... you have just discovered the tip of the iceberg...

having run both a one-size fits all suspension kit and a true tri 4link I designed, I will say that radius arm kits suck in comparison...

[rstrucks]

Can you guys that have completed a custom front 3 link or 4 link build post up some pics (or a link to a build thread) of your suspension? I think having some pics for reference would really add to the thread. If you have any that show mounting points at the axle and at the body/frame along with some "flex" shots, that would help people decide what route they want to go. Also, if you have extensively modified an existing "kit" post those pics too.

If you have measurements, angles, seperation, anti-dive %, etc... that info would help as well.

I know a lot of people (me included) are considering building a custom system and would like to see more info to help them decide what to go with (3 link, 4 link, radius arm).

[ZJ TINS]

One thought (may have been done already):

run the upper from stock axle location to back wall. place it as far down as you can go except keep the pivot point 6 inches above the lower arm pivot point.
run the lower arm in the stock axle location and run back 42+ inches to underneath belly. trade off ground clearance vs distance from top long arm pivot point to gain anitsquat.

I think I am going to get some 2 in pvc pipe to play with geometries and see what I come up with for clearances and such.

[zjeepin]

I'm going to be redesigning some of my rear suspension over the next few weeks. Im trying to figure out how to post up my calculator work along with pics so hopefully we can all learn something..

i've got my johnny joints in and link material so i'll be diving in over the weekend..

since this is a front suspension discussion should i start a new thread?

[rstrucks]

since this is a front suspension discussion should i start a new thread?

Nah, post up what you can. If need be I can move the info into the rear suspension TOTM that is not too far in the future, or we could even change the title of this thread to simply "suspension". The more you can share the better, we'll all benefit.

[SirFuego]

Im trying to figure out how to post up my calculator work along with pics so hopefully we can all learn something..

Print Screen takes a screenshot. Paste it into Paint and crop it.

If you have a Mac, I'm of no help...

[zjeepin]

Print Screen takes a screenshot. Paste it into Paint and crop it.

If you have a Mac, I'm of no help...

nah, im working in windows xp..

i got it pasted into paint with cams help, just gotta get it cropped small enough to upload and big enough to read.. will probably mess with it this evening..

[ATL ZJ]

Trey use this, it can both resize and host for you

http://www.imagesocket.com/

then just put [IMG] tags around the link like this [img]picname[/img]

or if you just need to resize, http://www.picresize.com/

[zjeepin]

Thanks, will do...