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Spring Over Versus Spring Under

Posted in How To: Suspension Brakes on June 1, 2009 Comment (0)
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It's like Coke or Pepsi, skiing or snowboarding, Democrat or Republican; the debate rages on. "Dude, you're stupid for buying that $600 lift kit when I can do a spring-over for $4 and some gum" Or, "hey, guy, unless you dump a ton of coin into steering corrections, new driveshafts, and a traction bar your $4 spring-over will kill every unborn kitten you drive it past." Really the truth lies somewhere between these two extremes.

Which school of thought is right and which is wrong? We ain't going there. But what we will do is share with you each Jp magazine editor's opinions on the subject as well as highlight some of the finer points of doing a spring-under or spring-over suspension setup correctly.

A heavier, more highly-arched pack used in a spring-over configuration such as this Hell Creek Suspensions FSJ pack will be less susceptible to axlewrap than a flatter spring. The tradeoffs can be (but aren't always) a slightly stiffer ride and less flex than a flatter, thinner pack.

John Cappa Says
I'll go out on a limb and say that 95-percent of the people who ask me about doing a spring-over on their leaf-sprung Jeep CJ or YJ are doing so because they think it's a cheap way to lift it. This couldn't be further from the truth. A properly-done spring-over suspension will be nearly double the price of a simple bolt-on lift kit. And the spring-over is much more labor intensive as well. Simply welding new perches on the top of the axles is the easy and cheap part. It's all the worms that creep out of the can afterward that gets expensive. Putting together a safe and solid steering system, replacing front and rear driveshafts, adding longer brake lines and shocks, and controlling axle wrap are all often overlooked when considering a home-job spring-over. And ultimately when it's all said and done you still end up with sagging, worn out, bent, or broken leaf springs. Plus, there is no such thing as a traction bar that doesn't bind. Don't believe me? Go ahead and flex your spring-over Jeep and try to remove one of the traction bar bolts. It ain't coming out because of the load it's under, no matter what kind of shackle or wacky contraption you put on the end. This bind results in spring fatigue and sometimes failure.

But if you go into a spring-over knowing it will cost more than a lift kit and you want the benefits of more articulation at a fraction of the cost of a four-link, then it might be a viable option if you are willing to accept all of the drawbacks. The spring-over is at least a good stepping stone until you are ready to run link-style suspension on your Jeep.

The number one problem I see happen with a spring-over is driveshaft binding and failure. Typically, whoever did the work attempted to install the longest shocks they could fit and never bothered to cycle the suspension. Raise the Jeep by the frame with the tires on and let the suspension sag. At full droop the driveshafts and yokes should not bind. If they do, you'll need to install limit straps or shorter shocks. If you don't have a traction bar of some sort at least on the rear you can expect to pick your driveshaft up off the ground several times a year. The axle wrap and resulting driveshaft binding often destroys U-joint straps and driveshaft U-bolts alike. Even the largest of U-joint assemblies will eventually fail. So if you've done a spring-over it's a good idea to inspect the yokes and driveshafts for bind damage after each outing. If you notice any out of the ordinary wear or problems, replace the parts and look into a more effective traction-control aid and/or suspension limit straps.

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In a front spring-over application, the position of the spring pack complicates the drag link mount on the axle. Avoid running a goofy S-shaped bend in the drag link to attach it to the tie rod or steering knuckle. The only correct way to do it is to run some sort of crossover steering arm on the top of the passenger-side knuckle to raise the drag link mount high enough to prevent spring pack interference.

Christian Hazel Says
For me, the biggest advantage to doing a spring-over is the ability to run a flat leaf spring. You can get nearly equal compression and droop from a flat spring, allowing for a cush ride and some impressive wheel travel from a modest lift height. Spring-over setups that use lift springs scare me because the center of gravity is raised so much. I've never understood why a Wrangler or CJ needed to be lifted 7 inches or more unless all you're doing is going in a flat, straight line through a mud pit. I also like supple spring packs, such as the factory 5-leaf Wrangler rear springs. Granted, the softer packs exacerbate the axle wrap problem in a spring-over, but it's been my experience that nearly any moderately-soft pack you run is going to wrap to some degree when used with big tires. And if you're using a pack that's thick and heavy enough not to wrap, you're going to be limiting your wheel travel, so why not just go for an easier spring-under setup?

That's why nowadays I prefer a spring-under suspension to a spring-over. They're easy, with no need for a complicated crossover steering arm to accommodate the drag link, no traction bars to counter axle wrap, and a huge selection of ready-made off-the-shelf and custom applications available for the choosing. That's not to say spring-under systems aren't without their caveats. For starters, the more highly-arched spring packs will require longer shackles because the spring has the potential to grow much more than a flat leaf spring. You'll also need to be wary of your axle U-bolts and leafs, as they'll be more vulnerable to damage from trail obstacles. And the spring-under will still require nearly all of the same brake line, driveshaft, and shock corrections and considerations as the spring-over. But at the end of the day, a properly selected spring-under suspension can offer nearly the same travel and comfort as a spring-over setup, but with a whole lot less fuss and muss.

Pete Trasborg Says
For me, being a guy with a moderate income and an overabundance of Jeeps, the important thing is the ability to build the spring-over lift as you go. Yeah, we aren't supposed to talk about it, but the reality is most of us are on budgets, and building a little at a time can be the only option we have available. Once you accept the fact that to make it work correctly you'll likely spend the same as you would for a spring-under lift, you can move forward.

Consider the need for the fabrication tools such as a welder, grinder and reciprocating saw at the very least and right away you are in the $500-$1,000 ballpark. Or, maybe you just bribe a buddy with beer and pizza until the job is done. Even if you have all the tools and steel needed, you will still need longer shocks, longer brake lines, a slip-yoke eliminator, driveshafts, and so on. Buying that stuff piecemeal is more expensive than in a kit.

If you are just mud-running, you can get away with lowering brake lines, and relocating shock mounts, or doing away with them entirely. That is, until you've got the cash for the right parts. Look, it won't handle well on-road, especially with no shocks, but around town it'll be fine, and some poor handling for a little while is better than a blown motor from a deep mud pit.

That said, I agree with Cappa about blowing up driveshafts. I've done it myself plenty of times thanks to my short-term cost-cutting methods and just flat-out not running a traction bar of any type. The other thing with using stock leaf springs in a spring-over configuration is that the springs will sag pretty quickly, and while I can likely find stock YJ springs for free, I have gotten really adept at swapping them out, and, if you use new u-bolts each time like you should, there are additional hidden costs there.

I used to be a fan of spring-under lifts just because I could put them together as the bank account allowed. Now I'm more inclined to cut sheetmetal before going through with a spring-over conversion.

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