Leaf springs vs. 4 link

[Justin]

I have a line on a well priced set of 12" travel coilovers for the rear of my rig. For a 60-70% street driven rig on 37s, what are the pros and cons of switching to a 4 link in the rear? The obvious one is more travel and flexibility off road and a better ride on road, but I'm not sure what the potential down sides are. I had planned to do more reading, but this has changed my timeline a little and any help is appreciated before I spend more money on the project.

[Kinder]

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[crawlercreations]

Ride quality is huge on the street. It rides way nicer on the street than my 11 leaf pack did. Rode better with softer Springs but had a ton of sway. Also there is no axle wrap at all so no worries with a hard accel. Being spooled it no longer jumps around turns, just smoothly let's the tire spin with out the hops the leafs allowed. Off Road is pretty obvious. Dirt roads with washboard are so much better too. My father in law was attempting to keep up with me on a very long dirt road once. He broke a front shock in his 2005 F- 150 in that attempt and couldn't go nearly as fast due to the bouncing. The road to Holy Cross is easy and comfortable to go as fast as I want. I wouldn't second guess doing a 4 link again. Easily one of the best things I've done to my bronco for street and off road. DO IT!

[Justin]

Thanks, I was hoping you'd chime in. Kirk, you may also want to check out the replies to the other places I've posed this. Nothing surprising, but they just went up this AM.

http://www.colorado4x4.org/vbb/showthre ... -vs-4-link
http://classicbroncos.com/forums/showth ... p?t=246354
http://www.pirate4x4.com/forum/general- ... -link.html

[landshark]

I would like to hear more as well.

I hear sway can be a bit extreme on the road without a sway bar setup on the rear. Is this true? What about weight in the back? What if your carrying allot of gear around, camping/hunting/ etc? I would love to do this as well but the simplicity and adaptability of the leafs are hard to beat.

I know jeeps landcruisers and icon broncos are all linked in the rear and seem to do just fine but see they run sway bars as well.

Not high jacking but curious to the advantages.

[crawlercreations]

I invite anyone to ride in my bronco for sway concerns. My Springs are pretty stiff so there is very little sway on the road. My load carrying capability is great. I've had over 800 pounds in the back several times and it handles the weight great with less sag than the leafs I had. Really I have yet to find a negative to the 4 link. Mine isn't even set up super great. I put quite a bit of thought into it but didn't work on the calculators too extensively.

[Justin]

Chris, one of the reasons I'd like to do coilovers is the ability to change preload to accommodate additional weight for long trips. Jason, I have to admit that your rig sways more than I'm used to, but my current setup corners really flat and handles well for a lifted rig. I'm guessing I'll be wanting sways with mine since I street drive it quite a bit more than you do yours. The level of stability your truck has does speak to how well it runs despite not having bars. 4-links are a fairly common setup for street use-just look at how many Jeeps are running around with factory coil rear suspensions. I'm wondering if the handling compromise is to run a less triangulated 3 or 4 link and a panhard/trac bar similar to Digger's setup.

[Kinder]

My big thing is that my Bronco has moved outside the norm, which is good, it's quickly becoming what I want in a all around vehicle. I've been daily driving it for over a year now, commonly load not only my camper and bronco trailer, but I also towed my flatbed w/ project 33x2 on it down to the springs. Over the last two weeks I've been scouting really hard in it, put well over 100 backroad miles on it in very demanding conditions, most of that time was in 4 high w/ some low mixed in when it got really nasty. I'm not too concerned with body roll, I don't hit corners very hard, even with the camper it's okay wth the current leaf setup.

So... is 4 link for me?

[crawlercreations]

Your rig, to me, is all about utility and simplicity. My opinion is that a 4 link is not for you. There would be no real world advantage you would see. You would get a nicer ride but in the end I don't feel a 4 link would add enough for you to go through the hassle of setting one up properly.

[Digger]

Awesome discussion so far. I'll toss in a few thoughts for what it is worth.

I would expand the conversation to include any arrangement of linked/coil suspension vs. leaf springs, including 2-link, 3-link/torque arm, 3-link/ radius arm, 4-link & 5-link.

Coils vs. Coilovers is another option to consider. Both have advantages and drawbacks.


Really the only reason to continue to run leaf springs is that they are so bloody simple to mount and cheap to replace. A linked suspension is 3x more complicated but the payoff is that you can divorce spring rate from suspension geometry from joint options, etc. The biggest downside to leafs is their internal friction. It plays hell when trying to adjust damping and spring rates because age and condition of the leafs are always changing the internal friction component.

Coil/linked suspensions on the other hand give you vast opportunities to do great things or screw it up royally. The biggest thing to remember is that most linked suspensions are built with race parts (like rod ends) and race parts are not designed for longevity or good ride quality because that is not important to a race car. This is why the OEMs use bushings and ball joints in their designs. They have to be concerned with more factors than a race car builder.

You should have ZERO concerns about sway and load handling. Those are just factors in the bigger equation. Load handling comes from spring rate. If you think you will be hauling 800 lbs, you would chose a spring rate geared towards, say 400lbs. That way your ride height would be within 1" of the designed nominal regardless of loading. You could also choose a progressive rate spring to help maintain ride height under an increasing load. BUT the truck sitting perfectly level takes a backseat to good handling when loaded.

Sway (roll stiffness) is determined by CG, roll center height, spring rate and distance between springs. Anti-sway bars are added last in the design when your package limitations prevent you from getting all your roll stiffness from the geometry and springs alone.

Personally I like track-bar equipped suspensions (if everyone hasn't figured that out already). Traditional 4-links usually have straight or slightly triangulated lowers and triangulated uppers. Lateral stiffness, which is key to good handling, depends on how triangulated the links are and how stiff the joints are. This is why race cars and trucks use rod ends. They have no compliance, so they are very stiff. However, now lateral stiffness is tied to longitudinal stiffness. With a track-bar equipped suspension, you can achieve different rates for lateral and longitudinal stiffness, which is helpful because you can make the suspension soft in the direction of travel for absorbing bumps from rocks and bridge seams and stiff laterally for good handling. Same goes for torque arms. I used ball joints on the rear mounts of my torque arm to make launches responsive, but bushings in the long arms to absorb rock hits.

Kinder - You shouldn't have any concerns with a multi-link suspension. Yours will just look slightly different because the geometry and spring rate would have to be adjusted for your wheelbase and loading.

[Justin]

Our conversation awhile back has had me thinking seriously about a track bar equipped rear suspension for the reasons you outlined above. It seems like there would also be better potential to control things like axle steer since you're also divorcing the front/rear and side to side movement of the axle through it's swing path. Also, can you speak a little more to coils vs. coilovers? My understanding is that the main differences is in the packaging, but I could see benefits to having the shocks operate on a different path than the springs.

[Jesus_man]

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x2 - so much to consider.

Mine works well as-is, but I'd like to move the rear axle back a few inches, try to eliminate the catch points (spring hangers) all while not sacrificing anything. I have my own thread to discuss, but I still have not decided and likely won't for a few years.

[Gunnibronco]

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x2 - so much to consider.

Mine works well as-is, but I'd like to move the rear axle back a few inches, try to eliminate the catch points (spring hangers) all while not sacrificing anything. I have my own thread to discuss, but I still have not decided and likely won't for a few years.

x3 Thanks for all the info. I'm reading along, and learning what I can. I'm very interested in a rear coil/linked set up. But its a ways off, probably, maybe.

Digger, I've been studying your build thread. Hope you don't mind me stealing your WH track bar riser mods. Above, you said you made your axle torque arm mounts with ball joints, but your long arm mounts with bushings. Looking at your thread, all your ends look to be your "custom modified" bushing ends. Can you explain further? I like the idea of running rubber bushings vs rod ends.

Is there an off-the-shelf bushed rod end you'd recommend over a heim for radius arms? Or any chance you might be going into the rod end business? LOL.

Thanks
Chad

[landshark]

Subscribed.

x2 - so much to consider.

Mine works well as-is, but I'd like to move the rear axle back a few inches, try to eliminate the catch points (spring hangers) all while not sacrificing anything. I have my own thread to discuss, but I still have not decided and likely won't for a few years.

I am in the same boat.. keep catching the spring hangers on stuff but I have been battling the cost/setup of going linked.. i like the idea but priorities keep popping up keeping me from getting serious about converting.

[Unaweep]

This is a great thead. I have been thinking about rear link set up also.

My buddy is selling his off road only Toyota and buying a Razor side by side, he said the ride is way smoother and he can cover more trails in a day vs. the slow and clunky truck.
That made me start thinking about upgrading the Bronco to ride much better and make the off road experience more enjoyable.


J.E.

[Digger]

Our conversation awhile back has had me thinking seriously about a track bar equipped rear suspension for the reasons you outlined above. It seems like there would also be better potential to control things like axle steer since you're also divorcing the front/rear and side to side movement of the axle through it's swing path. Also, can you speak a little more to coils vs. coilovers? My understanding is that the main differences is in the packaging, but I could see benefits to having the shocks operate on a different path than the springs.

The axle steer is one of the more minor factors, but with the good design you tend to minimize it. It is directly tied to the roll axis of the axle, which affects different parameters. For example, it determines whether the axle has natural under/oversteer, precession/recession, and how much the axle steers itself during suspension movement. For the rear, a downward angle gives you natural understeer, but is hard to package and most OEMs will give it a horizontal (neutral angle) or slight uphill angle so the when the axle hit a bump, it has a tendency to move back and up, producing a smoother ride.

On coils vs. coilovers:

Coilovers package very neatly. They are good for aggressive suspensions (high speed off road) The coils are very stable and they make it easy to switch springs or run dual or triple rates. The more advanced models like the pros use have position-based damping. The shock knows it is nearing the end of travel and is stiffening its damping curve to slow the suspension before bottoming out. However with a coilover the spring and shocks are tied together and use the same mounting points on the frame and axle, typically rod ends. Again, rod ends are for racing. They wear quickly and have no compliance, so there is no damping of the really high frequencies transmitted by the tires and axle. This can produce a harsher feel in the cab of the truck.

Conventional coils and shocks require a more complicated mounting system. But many shocks use rubber bushings to damp higher frequencies that the shock itself cannot remove from the system. The springs are separate from the shocks, so you are not limited to round coils. Leaf springs, coils, air bags, air shocks, magnets, rubber bands can all be used to support the sprung weight of the vehicle. The biggest advantage is that it typically requires less space to package conventional coils and shocks, and they tend to be cheaper.

With either system you can use a secondary suspension like a Jounce Shock (air bump) to control and disperse energy from the system right before suspension bottoming. This is similar to the position based damping of the coil overs.

[Digger]

Subscribed.

Digger, I've been studying your build thread. Hope you don't mind me stealing your WH track bar riser mods. Above, you said you made your axle torque arm mounts with ball joints, but your long arm mounts with bushings. Looking at your thread, all your ends look to be your "custom modified" bushing ends. Can you explain further? I like the idea of running rubber bushings vs rod ends.

Is there an off-the-shelf bushed rod end you'd recommend over a heim for radius arms? Or any chance you might be going into the rod end business? LOL.

Thanks
Chad

Go ahead and mod that WH design , my FEA modeling says it needs it if you are using the truck hard. (Plus just looking at vs. the stock unit gives you some indication)


Due to lack of marketing, the forged ends, cross-axis ball joints and bushings I'm using are a bit of an industry secret. So much so, that I'm the first person to actually build a vehicle with these joints. About two years ago I was starting out at my new job and was tasked with creating what is called a cross-axis ball joint for a popular car control arm we make. Most people know these joints as Johnny Joints, RE Joints, Ballistic Joints, etc. But the OEs are using them more and more to improve handling performance. It is simply a through-bolted ball joint.

Fast-forward to 1.5 yrs ago and our engineering dept made a push to create bigger versions of the original to compete in the off road after market with products like the Johnny Joint. The advantage my design has, it that it is OE styled. So it uses a Moly impregnated Nylon 6/6 race and rubber boots to seal the joint up from dirt and water. However most people look at it and think it's a bushing because of the rubber boots. Here is a cutaway of a smaller unit:


The forged receivers were designed later to provide a direct screw in replacement of the competition like Johnny Joints. To provide maximum flexibility, the receivers and xAxis Joints (our trade name for them) were sized base on standard Jeep control arm bushings. As a result, if you had aftermarket arms that used a Jeep bushing, you could press it out and put our joint in its place. This also works the other way. So I acquired several empty receivers and machined off the retaining lip and pushed a standard off-the-shelf Jeep TJ lower control arm bushing in its place.


The is another joint out there that I really like made by Metal Cloak called the DuroFlex joint. I had a chance to chat with those guys at Jeep Safari two year ago and it's a pretty solid idea. They shaped a bushing to give greater articulation and packaged it in a threaded receiver.
http://www.metalcloak.com/Jeep-Suspension-Builders-Parts-s/235.htm




If is wasn't for my ability to stuff Jeep bushings into readily available receivers, I would have purchased the DuroFlex joint to use in conjunction with my own.

[Gunnibronco]

Cool stuff. Thanks so much for the expert info.

If/when your stuff is available, let us know. I know I'd like to support the local economy.

[Justin]

x2. How do we get our grimy hands on these? I really like the idea of having some extra cushion in the suspension joints, and am a huge fan of anything that's sealed against grit.

[Gunnibronco]

Here are their ball joints:

http://www.amazon.com/s/ref=nb_sb_noss? ... IS%20JOINT

Their web site:
http://www.spcalignment.com/home/291

[Digger]

Here are their ball joints:

http://www.amazon.com/s/ref=nb_sb_noss? ... IS%20JOINT

Their web site:
http://www.spcalignment.com/home/291

Those are the parts. Send me a PM if you are interested in any purchases. I don't make any money off of these, but I can point you towards some better pricing.