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Suspension Joints Exposed and Explained

Posted in How To on February 1, 2013 Comment (0)
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Details make the difference, a cliché that rings especially true in the case of suspension joints. There are a variety of suspension joints on the market, and one type does not fit all applications with the same aplomb.

This isn't a shootout. It’s a look at what’s available and the features and benefits of each type of suspension joint. While you’re testing your mettle on the trail, they’re rotating and articulating under your rig.

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Most stock vehicles come with rubber bushings from the factory, such as the upper and lower rear links from our 2004 4Runner. Rubber bushings have their downsides, but they’re desirable on a stock rig seen at the dealer lot. Why? Rubber bushings run silently, and they help insulate the vehicle body from road noise and vibration. Rubber bushings do not rotate or articulate, per se. The rubber is vulcanized and therefore permanently attached to the inner eyelet and outer sleeve of the suspension member. As such, the rubber distorts and twists rather than actually rotating or articulating. This quality also means rubber bushings resist movement and can actually limit suspension travel. Another downside is that much of the time you can’t just replace the bushing when it wears out. Instead, you’ll likely have to replace the entire suspension part.

Rod ends (aka Heim joints) are extremely popular in aftermarket and custom suspensions. They’re available in many sizes and are suitable in many suspension locations. For suspension applications, high-quality rod ends that incorporate a Teflon liner between the ball and the socket should be considered essential. The high-quality, Teflon-lined rod ends last longer, run smoother, and transmit less noise.

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Rod ends allow generous amounts of articulation between the threaded shank and the ball, provided you install a pair of high-misalignment spacers into the bore.

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One of the reasons rod ends are so popular in high-performance applications is that they’re so versatile and can be used in steering applications. In this case, a rod end was used to splice a non-matching tie rod and draglink together during a steering-box swap. Bolt-on parts wouldn’t work here, so some custom fabrication and a carefully placed rod end did the trick.

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If you want ultimate suspension geometry control through the complete suspension cycle, you’ll want rod ends (or spherical bearings, but we’ll get to that in a moment) along for the ride. This Early Bronco bristles with rod ends at every suspension pivot. The shocks are mounted to the links below the pivot plane’s centerline so the rear links don’t flop side-to-side.

The spherical bearing is often called a “uniball,” but the two words describe the same thing. Spherical bearings use the same ball-and-socket construction that rod ends do. The difference is that the spherical bearing is housed in a cup rather than in a housing with a threaded shank. The spherical bearing’s cup is welded to the suspension member.

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There are times when gobs of articulation can be too much of a good thing. One way to limit articulation is to use the “wobble stopper” from Kartek Off-Road. The Wobble Stopper is simply a spherical bearing equipped with a pair of Delrin inserts that prevents the bearing from articulating past a certain point. The spherical bearing itself is otherwise the same. The Wobble Stopper comes as a kit that you weld into your suspension part and is most commonly used at the frame end of lower rear suspension links on desert trucks.

The heat of welding can distort the spherical bearing cup. To minimize the distortion, temporary inserts can be installed into the cup during welding, acting as heat sinks.

Urethane bushings, seen in red on these Total Chaos suspension links, are economical and durable. Like rubber bushings, they provide a measure of damping between the suspension and the chassis. Like rod ends and spherical bearings, they truly rotate rather than merely distort the way rubber bushings do. Urethane bushings also articulate, but not that much. Many times, you can save money by placing a urethane bushing on one end of a suspension member, and a rod end or spherical bearing on the other.

Urethane gets squeaky if it runs dry, so it needs to be greased at regular intervals. Some grease types are better than others, but the interval frequency matters more than what kind of grease is used.

Urethane bushings are available as builder parts from companies such as Synergy Suspension and Autofab. A typical bushing kit consists of an outer sleeve, two bushing inserts, and an inner sleeve. Many bushing kits also include the bolt. When the bushing halves wear out, they can be replaced separately. Urethane bushing assemblies are versatile creatures. Autofab’s extensive line of motor mounts is based on urethane bushing assemblies. In addition to urethane bushing assemblies, Synergy Suspension offers rod ends and spherical bearings as builder parts.

Brainstorming about a suspension joint that offered the articulation of a rod end and the cushioning and easy maintenance of a urethane bushing gave rise to the Johnny Joint. The Johnny Joint is a ball-and-socket joint, but instead of steel, the ball is encased in a urethane socket. The Johnny Joint is a Currie Enterprises innovation and is named after John Currie. This style of joint has become very popular and “Johnny Joint” has almost become a generic term. Only Currie Enterprises offers genuine Johnny Joints.

As seen in the previous photo, Johnny Joints are available with threaded shanks, and weld bungs are also available from Currie Enterprises to help create custom suspension links. If your needs call for a thread that’s not in Currie’s wide selection, you can get the Johnny Joint without a threaded shank and weld a bolt onto the cup. This is not a welding project for beginning welders, though. If you doubt your welding ability, leave a project like this to a pro.

Johnny Joint sizing refers to the outside diameter (OD) of the cup. Inside, you’ll find a ball center, a pair of replaceable urethane bushings, retaining washers, and a snap ring. The 2-inch Johnny Joint on the left is commonly used for axle track bars (aka Panhard bars) while the 3-inch Johnny Joint on the right is saved for severe applications such as fullsize desert trucks and rock rigs using 1-ton axles. Not shown is the 2-1/2-inch Johnny Joint. The uses are only limited by your imagination, so contact Currie and let them help you with your brainstorm.

Currie recently introduced a high-performance Johnny Joint that boasts features beyond the original. A micro-polished ball center runs cooler during high-frequency suspension cycling (think desert whoops). The housing is CNC-machined from 4140 chromoly steel for extra strength and is radiused at the edges to fit and move in tighter confines. This is a 2-1/2-inch high-performance Johnny Joint.

The Johnny Joint comes in sizes up to 3 inches. This 3-inch Johnny Joint sees harsh duty under the Sato Brothers Racing F-150. It’s being used as a radius arm pivot in a twin I-beam front suspension.

Rubicon Express has a suspension joint all its own. A ball-and-socket variety, it’s called the Super Flex joint. Instead of urethane, the ball is encased in UHMW (ultra high molecular weight) nylon inserts. This type of nylon is very slippery, providing free and easy suspension movement. The UHMW inserts provide greater load-carrying capacity compared to urethane. They’re also more rigid, so they transmit more vibration than urethane does. Super Flex joints are part of multiple Rubicon Express suspension kits and are also available a la carte as builder parts.

Super Flex joints are captured in their housings via a pair of threaded collars. You’ll need a Rubicon Express four-pin driver to turn the collars. As the nylon inserts wear, you can compensate by tightening the collars.

When multiple companies are devising ways to innovate, it only makes the marketplace better. The MetalCloak Duroflex joint looks like a familiar part, but it’s got some key innovation up its metallic sleeve. The center of the Duroflex joint is a metal inner sleeve fused to an elastomer outer casing. This is the core of the Duroflex joint. Like OEM rubber bushings, Duroflex joints run silently and absorb noise and vibration. However, the Duroflex joint is made of a material that’s soft enough to articulate. Furthermore, the Duroflex joint is not fused to the outer housing, so it can rotate, as well. It’s an ideal combination of rotation, articulation, and shock absorption. Duroflex joints require special synthetic grease also available from MetalCloak.

Duroflex joints are part of MetalCloak’s suspension systems, but they’re also available as builder parts. The fused center bushing is available separately, so it can be replaced as needed.

Dave’s Customs Unlimited offers the Roc Joint. It’s a urethane bushing assembly that comes with a threaded shank on the housing, so it’s ready to attach to a custom control arm. Inside the Roc Joint is a pair of uniquely shaped bushings that allows misalignment well beyond a standard urethane bushing assembly. A grease zerk provides easy maintenance and lubrication.

To go with the Roc Joint, Dave’s Customs Unlimited also offers an axle bracket that’s specially built to the Roc Joint’s dimensions. Quarter-inch-thick steel plate is abuser-friendly.

Sources

Currie Enterprises
Corona, CA 92880
714-528-6957
http://www.currieenterprises.com
Dave's Customs Unlimited
Fruita, CO 81521
970-216-8179
www.davescustomsunlimited.com
Rubicon Express
Rancho Cordova, CA 95742
877-367-7824
www.rubiconexpress.com
Total Chaos Fabrication
Corona, CA 92880
951-737-9682
www.chaosfab.com
MetalCloak
Rancho Cordova, CA 95742
916-631-8071
www.metalcloak.com
Autofab
Santee, CA 92071
619-562-1740
www.autofab.com
Synergy Manufacturing
San Luis Obispo, CA 93401
805-242-0397
www.synergymfg.com
Kartek Off Road
www.kartek.com

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