Choosing Your Suspension - Poison PickingPosted in How To: Suspension Brakes on June 1, 2009
Everybody has a favorite. Some guys are content to slap on a dime-store lift and call it a day, while others wanna continually tweak and fabricate until perfection is reached. Still, other guys just throw booty-fab and booger welds at a frame until the axles can flex clear to the other side of the vehicle, spitting coils and snapping brake lines in the process.
Which is right for you? Well, that largely depends on your design and fabrication abilities. Although we're discussing certain pros and cons of suspension types, keep in mind that the simplest well-designed stock suspension will work much better than a complicated, yet poorly designed crazy-fabbed suspension.
John Cappa Says
A well-thought-out four-link suspension like what can be found on the front and rear of TJs and Grand Cherokees and the front of XJs and MJs is perhaps the best-performing off-road suspension your Jeep can have. However, a poorly-engineered home-built four-link with little consideration for spring rate, anti-squat or roll-center will perform worse than any factory leaf spring suspension. So if you have no idea what these terms mean, you have no business building your own four-link. Your efforts will likely result in an overly-flexy RTI ramp champ that's worthless in the real world and scary out on the trail.
A custom triangulated three-link suspension is a great way to simplify a rear suspension and eliminate the sometimes problematic track bar. Although, a four-link rear suspension with a track bar will typically handle better on- and off-road. The track bar locates the rear axle better. A triangulated three-link is not a good idea up front. Your turning radius will be adversely affected and there will be noticeable bumpsteer unless the steering has been completely redesigned to cycle and move in sync with the suspension. You are better off with a three- or four-link with a track bar if you plan to use the conventional steering box and crossover steering commonly found on most Jeeps.
When a link-style suspension is utilized there are a number of different springs that can be used to support the Jeep and provide suspension travel. The simplest and cheapest is a stand alone coil much like what you would find in the front or rear of a '97-present Wrangler. The coils are located by brackets that are welded onto the frame and axles. Spring rate and lift height are limited by the coils that are available for your brackets. Coilovers are a little simpler to mount, but they offer the advantage of a shock and coil in a nice compact unit. They are also much more expensive and infinitely more adjustable in terms of spring rate and valving, giving your Jeep nearly unlimited possibilities based on what it weighs and your driving style. Air or nitrogen shock springs are not a good option for a Jeep that sees real world trail use. They can heat up during faster trail sections causing the spring rate to increase. This will cause your suspension to perform less than ideal in a given situation. An often untapped spring for a link style suspension is the leaf spring. By combining a leaf spring hung on two shackles with a properly designed four-link you end up with an extremely predictable and stable suspension that provides great performance. It is, however pretty complex and can be significantly heavier and harder to install than a coil-over or stand-alone coil spring.
Christian Hazel Says
Like anything, it's easy to base your opinion of something off of a poor example. Somebody who has eaten at Del Taco may think they don't like Mexican food, somebody who has had a rough flight with lots of turbulence may think they don't like airline travel, and somebody who has been to France may think that all French people, well, that's not a good example. Point is, when passing judgment on any given suspension design, you've really got to ride or drive a properly-executed example to make a real determination.
To borrow Cappa's penchant for percentages, I'd bet 95-percent of all off-roaders haven't driven or ridden in a properly set-up link-type suspension unless it's been in a totally stock, factory vehicle. For years, I've been watching poorly-designed link-type suspensions spit coils, induce axle chatter, break components, and nearly tip over at the slightest angle. I got hardened and made up my mind that anybody not running the Baja 1000 should have leaf springs and that's that. But that's not that
For most wheeling situations, there's nothing wrong with a leaf springs. They're simple, they work, and they're reliable. They're the lazy man's suspension and that's why they're my personal favorite. I always say if you run a locker(s), there's no need to keep all four tires planted on the ground all the time. But as my wheeling preferences shift from rocky trails to going fast, I'm developing an ever-increasing appreciation for link-type suspensions and what they can truly do. And while a coil or coilover suspension will never be as predictable as a leaf-sprung suspension with its progressively-increasing spring rates, I'll admit that a properly-designed link setup can run head-to-head with the leaf setup anywhere, and then some.
A correctly-designed link suspension will floor you with its abilities. When I say correctly-designed, I'm not only speaking of geometry, but shock valving as well. Regular coil springs are a cheap way to gain some good flex, but personally I'm into coilovers. Their compact design, flexibility, and capacity for outrageous performance draw me like a moth to flame. I'm getting less lazy about suspension design and building, as I bet most enthusiasts are. While a few years ago I would have scoffed at the thought of internal or external bypass coilovers and thought 18-20 inches of wheeltravel superfluous, nowadays I'm seeing there's more than just rockcrawling and mountain trails out there.
Pete Trasborg Says
Unlike some others here, I hate track bars. I've had more track bar-related problems with mounts torn off axles, frames ripped or cracked, seized bolts, wallowed-out holes, and on and on. Sure it works; and sure you get tons of flex out of it, but what a pain in the butt.
The alternative, of course, is a triangulated setup, be it a three-link, or four-link. You get rid of the track bar, but then it often seems like everything else under the Jeep is in the way of where the link arms need to be. Of course, that results in compromises with link length and frame-side link mount locations which then messes with your squat, anti-squat, and roll center. I've yet to meet or talk to a guy that's home-built his link setup and didn't want to change it after he was done the first time or first few times. Talk about being married to a Jeep, after you put all that time and effort into designing the system, you need to pull it all apart again (often many times) to nail down the way it should be. Or, the more likely scenario is that people will just train themselves to deal with the shortcomings of their setup.
Don't get me wrong, I'm not all doom and gloom on coil sprung/linked setups. They handle washboard and crappy highways like few leaf springs ever could, and if you could stick with the constant prototype loop long enough to get it nailed down it works great. The two major downsides that will keep me away from a custom front and rear link setup almost every time is the long road to having it be dialed-in, and the lack of feedback or "loose" feeling in off-camber slow-speed situations. If I'm building my own suspension, give me a leaf spring and a reciprocating saw any day and I'll see ya on the trail in a few months.