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Spring Over Versus Spring Under

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JP Staff | Writer
Posted June 1, 2009

Spring-Over Or Spring-Under?

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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