TOTM: Front suspension

[rstrucks]

Alright guys. Here's the topic, lets talk about it. Try to stay focused on tech and past experience on what works and what doesn't. I thought about going with a suspension thread in general (to include the rear) but I thought there is plenty of material to cover on just the front. So lets kick around some ideas about radius arms, three links, four links w/ panhard bar and triangulated 4 links. I know there is a seperate discussion about what exactly constitutes a "link" and if a panhard/track bar counts towards the total, but for the sake of simplicity lets assume that a panhard/track bar does not count.

Post up pics of what you did, how you did it, what you like, what you don't, why you "upgraded", the geometry, etc.....

[ATL ZJ]

thanks for taking this over Ryan. we're off to a good start on the panhard classification

Caster takes precedence over pinion angle

Tri 4 link > 3 link > claytons "radius" arm > ford radius arm > shortarm > stock garbage

front axle in front of crank pulley for maximum performance and best weight dist.

shoot for 7-8"+ of vertical separation

[downtowncb]

... 3 link > claytons "radius" arm ...

Along these lines, has anyone converted a Clayton radius arm to a 3 link? It would be a tight squeeze but I think you might be able to fit an upper on the driver's side. Just been rolling around my head for a while.

Why exactly is a 3 link better than a radius arm? I've heard because it unloads on steep stuff but why? If I were to route my winch for suck down duty on my Claytons setup would that be about as good as a 3 link?

From my personal battle to eliminate bump steer and potential sources of death wobble. When designing a front end from scratch, make the track bar (from bolt to bolt) and the drag link (from center of TRE to center of TRE) the same length and as close to parallel as possible.

This took some revision to get perfect.

[AgitatedPancake]

I've been pondering the same question about claytons, and I don't see why not. I'll most likely be doing a 3 link when I do the 609.

There is one catch though, and I've pondered it for a while...as you know with a 3 link it is recommended to have hard joints (such as heims or johnny joints) on all ends of both lowers and the upper, to avoid the looseness inherent with bushings, as it's the most apparent on a 3 link setup. Do you think you can successfully/reliably get away with possibly doing poly bushings on one end of both the lowers? I'm talking like replacing the clayton LCA bushings with poly's and use the lowers for the 3 link.

I mean I know this setup would "work", but how would it feel on the road? Would the polys be firm enough to hold up to having a single upper link, especially if the upper has hard joints on both ends?

[jfowlzj95]

There is one catch though, and I've pondered it for a while...as you know with a 3 link it is recommended to have hard joints (such as heims or johnny joints) on all ends of both lowers and the upper, to avoid the looseness inherent with bushings, as it's the most apparent on a 3 link setup. Do you think you can successfully/reliably get away with possibly doing poly bushings on one end of both the lowers? I'm talking like replacing the clayton LCA bushings with poly's and use the lowers for the 3 link.

Been thinking this same thing, as I'm running Ballistic's poly joints on the front lowers. Was thinking about just going ahead and keeping the lowers as is and using heims on the upper.

[OverkillZJ]

FWIW: I tried a single upper link with a large grade 8 bolt and poly bushings - it worked for awhile but I chewed up bushings. I think heims or johny's (I know they're kind of poly) would work much better.

Obviously some of you know about the first fiasco where it didn't work when I accidentally put a grade 5 bult in the single upper, and it broke.

[rstrucks]

Along these lines, has anyone converted a Clayton radius arm to a 3 link? It would be a tight squeeze but I think you might be able to fit an upper on the driver's side. Just been rolling around my head for a while.

Why exactly is a 3 link better than a radius arm? I've heard because it unloads on steep stuff but why? If I were to route my winch for suck down duty on my Claytons setup would that be about as good as a 3 link?

I will soon be converting my Rusty's radius arms to a 3 link. I plan on installing forged flex joints on the axle ends to replace the OE style rubber bushings and removing the arm bracket for the upper links. I then plan on building a new third link, again using flex joints, and mounting it next to the t-case linkage on the driver side. I may have to modify the floor pan to do so though. The other end will mount to the top of the diff housing.

The 3 link is better than a radius arm set up because of less binding. When a radius arm moves through it's arc of travel the axle will obviously follow that arc. The problem comes in when the other side is staying put or articulating in the opposite direction. Because both upper arms are fixed the bushings have to deflect to absorb some of the difference or you will twist off a mount as the arms in effect try to twist the axle tube. That is why my axle end lower arm bushings are shot. I haven't replaced them either because I figure the bushings need this and I have plans on replacing the radius arms anyway. As far as the unloading goes, I haven't really noticed that too much. I have seen a number of radius arm suspensions axle hop a good bit.

[Cody]

I've run lengthened and jointed radius arms on the front of my last 3 ZJs. The buggy was triangulated radius with 1.25" heims at the frame, the 93 was Clayton/RE style "Y" radius arms with Tera joints at the frame, and my current one is lengthened ford arms with Tera joints at the frame.

All three used triangulated rear suspensions, and the two full bodied ZJ's used identical rear suspensions and even though the execution on the radius arms was different ("Y" arm style vs. true radius) they both behaved very similarly.

All that being said, whether you use radius, 3 link, 4 link or anything else, I've found the thing that makes the biggest difference in how the rig can climb is a center limiting strap. I can't overstate how much of a noticeable difference this simple modification makes to a front long arm suspension.

Weld a tab to the center of the axle, and route the top to the motor mount. Buy a strp that will leave about an inch of slack at ride height. Motor mount may not sound ideal, but I haven't had a problem in 8 years of doing it this way.

[OverkillZJ]

X2 on the center strap - made a world of difference on my junk.

[downtowncb]

All that being said, whether you use radius, 3 link, 4 link or anything else, I've found the thing that makes the biggest difference in how the rig can climb is a center limiting strap. I can't overstate how much of a noticeable difference this simple modification makes to a front long arm suspension.

Ok cool, so it would seem that using my winch as a suck down winch would accomplish this effect while not loosing down travel while going fast.

[Cody]

Ok cool, so it would seem that using my winch as a suck down winch would accomplish this effect while not loosing down travel while going fast.

It sure would, but I found it far easier to weld a tab and play with 2 bolts than it was to safely route a winch cable around my bumper and through the steering in my front end. Obviously if you start from scratch you can engineer the solution.

I drive plenty fast, and quite honestly 90% of my offroad mileage is in the high-range, back-road-bombing variety, and my front strap is 100% transparent to me.

I will note, that I've had one for so long I may not know what it feels like without it.

[faststang1]

I been thinking of a 3-link for a while to,but then again my claytons works awsome.but I want to try a 3 link.I have talked to clayton and there going to build a 3 link upgrade for the ZJ.there going to use a 2.5 JJ with a 9/16 bolt at the axle end and at the frame.

[IndyZJ]

I've been pondering the same question about claytons, and I don't see why not. I'll most likely be doing a 3 link when I do the 609.

There is one catch though, and I've pondered it for a while...as you know with a 3 link it is recommended to have hard joints (such as heims or johnny joints) on all ends of both lowers and the upper, to avoid the looseness inherent with bushings, as it's the most apparent on a 3 link setup. Do you think you can successfully/reliably get away with possibly doing poly bushings on one end of both the lowers? I'm talking like replacing the clayton LCA bushings with poly's and use the lowers for the 3 link.

I mean I know this setup would "work", but how would it feel on the road? Would the polys be firm enough to hold up to having a single upper link, especially if the upper has hard joints on both ends?

I've been wondering about the same thing. I've always read that you need all "hard" joints in a 3 link (w/ panhard) because any give would lead to unwanted axle movement, specifically rotation. The IRO kit with a single radius arm has made me wonder though, because it essentially has the same kind of attachment to the axle. It uses all rubber mounts at the axle and I haven't heard any complaints of bad road manners yet. I have driven an old Ford with a wristed radius arm setup that is essentially the same idea, and it felt very sloppy compared to a normal radius arm or link setup. The only thing I can figure out is that the IRO kit has enough seperation at the axle to make a difference and the solid radius arm must help to a degree, too. That or nobody with the IRO kit knows any better

When I get to the ZJ, I really want to go to a 3 link, but I may have to go with a mid-arm setup because I'm not going to run more than 3" of lift and I really don't want to run radius arms because of the bushing-killing binding and potential unloading. Unless I run a very bent upper or severely hack the floor, I don't think I'll be able to fit a true "long arm" 3 link. With so little lift, I'm thinking I wouldn't have the anti squat/dive issues associated with radius arms, but I'd rather go with a 3 link if I can make it fit. I may end up giving in and going with a single-sided radius arm design similar to IROs, but a little beefier and with hard joints instead of the goofy caster adjuster they use and factory bushings. It'll come down to whatever I can fit without a ridiculous amount of work. Either way it will get a center limit strap like Cody suggested.

As far as 3 link setup goes, I'd go with what ATL posted and just run as much seperation as you can make fit at the chassis side (assuming we're talking about full-body ZJs/WJs). The best results seem to come from making the upper link as close to horizontal as possible.

Has anybody run this? It looks to be the pre-made solution that uses the biggest bolt (14mm) in the D30 cast-in upper mount. Genright usually only sells high-quality stuff but the RK name makes me wonder.
http://www.genright.com/ProductInfo....ductid=SUP2100
The other option I know of is a Johnny joint that uses a 1/2" bolt and presses in.

[FortCollinsZJ]

I had been wanting to upgrade from the radius arm Claytons, to a three, or fourlink, and decided to go the way of a fourlink, my uppers both have a 15* bend in them (passenger side needed to clear the exhaust) I had to trim the pinch on the inside of the frame rails on both sides, and weld the "frame" back closed. I also used a holeswaw to cut a clearence in both frame rails to insert a piece of tube to act as bolt pass throughs for the frame side upper bolts. After getting it all in and testing the flex, it is outstanding, with no bind in any normal amount of travel, tested at 14" droop (shocks disco'd), and full bump. The pinion angles are acceptable through the entire travel range.

Any brake steer that I had before is gone completely. It handles ALOT better on and offroad than the radius arm setup ever did. I have had one shake down run on a rocky trail at speed, and it was very predictable and better described as "tight". I have yet to test it in a rock crawling scenario, that will happen this weekend.

I chose the four link over the three for the simple reason that I didn't want to have to trust a single 1/2" bolt on a single upper. And for the fact that a three link is more prone towards brake steering than an four link.

I will have to get some pictures soon, I am very pleased with the way it all came out.

[jfowlzj95]

Here's a question for those who want to convert Clayton's to a 3-link.

At the body/frame, would you mount the upper on the center cross-member piece? Think it would be a strong enough spot to mount an upper to with 4 grade 8 bolts and the transmission holding it into place. Or would you mount it at a more 'fixed' spot, like the inner frame rail or maybe even on top of the outer cross-member piece where the lower mounts? If there is enough room there, would most likely consider a heim in this situation.

[FortCollinsZJ]

Mount it to the "fixed spot" Not on the removable section. That would be a PITA everytime you want to remove the center section. The center section also has no room, the driveshaft hovers right over the spot you would be placing the link mount. One glance under the jeep and it's worth a thousand words.

[downtowncb]

I had been wanting to upgrade from the radius arm Claytons, to a three, or fourlink, and decided to go the way of a fourlink, my uppers both have a 15* bend in them (passenger side needed to clear the exhaust) I had to trim the pinch on the inside of the frame rails on both sides, and weld the "frame" back closed. I also used a holeswaw to cut a clearence in both frame rails to insert a piece of tube to act as bolt pass throughs for the frame side upper bolts. After getting it all in and testing the flex, it is outstanding, with no bind in any normal amount of travel, tested at 14" droop (shocks disco'd), and full bump. The pinion angles are acceptable through the entire travel range. ...

Get some pictures up ASAP please. I remember when you were posting up CAD drawings of your ideas a while back, or at least I think it was you. Glad to hear you made it into a reality. Why do you say a 3-link tends to brake steer?

[jfowlzj95]

Mount it to the "fixed spot" Not on the removable section. That would be a PITA everytime you want to remove the center section.

Agreed it would be a PITA, but for just a single upper I don't think it would be too bad. There are actually some designs where they mount the upper and lowers to the transmission cross-member.

The center section also has no room, the driveshaft hovers right over the spot you would be placing the link mount. One glance under the jeep and it's worth a thousand words.

What if you were to run a pass drop axle and tcase? I'm planning on going this route, looks like it would free up a ton of space to mount that upper on the drivers side.

I am in favor of mounting the upper on the inner frame rail, just curious if that center piece would be strong enough for the single upper the way it mounts to the other pieces, or would it just be more prone to failure. We've all seen what happened to Matt's buggy when that bolt to his upper failed.

x2 on getting pics of yours ASAP. After seeing your planning on it, it's become my back up plan if I decide to ditch the 3-link.

[FortCollinsZJ]

Here are some bad cell phone pictures I just snapped. These are pretty much all passenger side pictures. Packed pretty tight in there, but it all fits no problem.














DownTownCB, I took off a single upper off of my radus arm setup for a day to see how it felt, under HEAVY braking, the axle would pivot on the soft rubber on the axle end of the lower CA's and would cause a bit of steering slop and a pull to the right. I have heard of it being similar with a three link with any poly or rubber in the setup. I just wanted a setup that would eliminate as much movement as possible.

[IndyZJ]

Get some pictures up ASAP please. I remember when you were posting up CAD drawings of your ideas a while back, or at least I think it was you. Glad to hear you made it into a reality. Why do you say a 3-link tends to brake steer?

If it's what I'm thinking about (and the possibly the scariest part of driving a rig with wristed ford radius arms), brake steer is to what happens under hard braking and the suspension has an uneven "give" to it from one side to the other. Under braking the axle tries to rotate forward and the links try to keep it from doing so. With an "incorrect" setup (usually soft joints, not enough seperation, lowers too high, etc.), anti-dive acts predominantly on one side of the axle, allowing one side to dive while the side with the upper fights it. I've only seen this complaint from people who have joints with any kind of significant give in them and/or have the lowers mounted at or above the centerline of the axle, giving the lowers little to no leverage against the axle trying to roll forward under braking.

With a 3 link w/ panhard, if the lowers are at the axle centerline, the upper has to counter most, if not all of the rotational force of the axle. Since the upper pretty much has to go on one side, the force will try to act on that side of the axle. Heims for every joint should keep any deflection from happening, but it would be more "correct" to mount the lowers below the centerline and make them do some of the work. That's what makes sense to me anyway from seeing and driving a few different setups - some good, some not so good.

Hope that makes sense. Drive a bad setup and you'll understand very fast. I have way too much freetime lately to do way too much research on this stuff...

[rstrucks]

Questions I'd like to see answered:

What kind of seperation should you shoot for at the body/chassis end of the links?

What about link length? I thought the upper link should be around 70% of the lower is that correct?

You can put the third link of the passenger side right? I can't think of a reason not to. There may be a little more room on that side so it may be a viable option. You'd obviously have to build a very strong mount since it will be taller than a mount on the driver side but beyond that is there any downsides to a pass. side upper?

[ATL ZJ]

What about link length? I thought the upper link should be around 70% of the lower is that correct?

not necessarily. That's what I made mine because I was told that having uppers ~70% the length of the lowers keeps the pinion angle constant throughout the range of travel (and it seems to work), but it's not a hard and fast rule. But nowadays you see a lot of rigs running equal length uppers and lowers so they can carry one spare link that fits in every location...

You can put the third link of the passenger side right? I can't think of a reason not to. There may be a little more room on that side so it may be a viable option. You'd obviously have to build a very strong mount since it will be taller than a mount on the driver side but beyond that is there any downsides to a pass. side upper?

"Let me answer your question with a question"... should the axle-side panhard mount be on the opposite side of the axle-side attachment of the upper link in a 3 link? Or does it even matter? I have never built one personally, but if so, I suspect this is why you see upper links on the driver side in rigs with driver drop axles...

[SirFuego]

I don't have much to add to this discussion due to only have experience with Clayton's radius arms, but I will say this.

My front uptravel is only about 1/2" more than stock (5" bumpstops on a 5.5" lift) and my downtravel is limited (by limit straps at each side of the axle) to where the coil spring just unseats. I haven't checked my bushings in a month or so, but I haven't noticed any real wear issues with them in the 2+ years I've been running my Clayton's setup that way. The primary reason for setting it up that way was to be able to turn at full stuff and also to keep front driveshaft in check. The bushings seem to be a nice side effect of setting it up that way, though. The geometry of radius arms make them bind -- there is no doubt about that, and I'm not saying that my setup is ideal (I wouldn't mind more droop for going over ledges) but I'm just throwing that out there because they can be setup to prolong the life of the bushings.

One more thing -- I know folks have beat on 3 links HARD without failure, but I'm personally leary of only running 1 upper in the event that it fails. Also keep in mind that in a 3 link, the upper arm sees more force than a 4 link, so be sure to brace the upper brackets accordingly.

Cody -- how much droop does your center limiting strap allow?

[ATL ZJ]

I will also agree with Cody et al that the center limit strap is the best thing since sliced bread. I use my winch for it, which is nice because it's adjustable, but the motor mount straps work too. I just prefer the winch because I can cinch it down to have about an inch of slack on steep climbs and use my full 10" of droop when I'm haulin arse

[Cody]

Cody -- how much droop does your center limiting strap allow?

Maybe an inch? I can get a picture tomorrow. I have to work on the rig a little to get it ready for fall wheelin season