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Suspension Bushing Basics

Posted in How To: Suspension Brakes on May 1, 2011 Comment (0)
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Photographers: Fred Williams

Every suspension system has a point where it pivots or flexes. This is true for independent, leaf-sprung, and multilink suspensions. While each suspension design works differently, they all rely on a flexible joint to allow the system to cycle without binding or breaking.

At the OE level, many of the top manufacturers use a compound rubber joint as their pivot bushing of choice. This is largely due to its durability, vibration damping, and low cost to manufacture. In the aftermarket, however, there is a variety of joints to choose from. And while many suspension manufacturers produce their own branded joint, most of the basic features and characteristics of both rebuildable and non-re-buildable joints are the same.

To help you determine what's the best joint for your rig, we've broken down some of the most popular endlink styles into their respective categories and listed the pros and cons for each.

Heim Joints
Heim joints, or spherical rod ends, are one of the most commonly used joints in the aftermarket. From suspension endlinks to transfer case linkages, these non-rebuildable joints range drastically in strength and size. A Heim joint's basic design consists of a swiveling steel ball that's pressed inside of a forged steel body. To help the ball rotate freely, some choose to inject a plastic filler or set in a Teflon liner.

Misalignment spacers are commonly used to center the joint so it can achieve the most degrees of rotation. A high degree of rotation means greater flexibility and less bind during articulation.

When used in suspension setups, Heims are often best suited for competition only or dedicated off-road vehicles, as their high strength and mostly steel design tend to transmit more vibration. This robust metal design also tends to be affected more by the elements than flex joints or bushings are.

Pros
•Generally low cost (depending on size and type)
•Versatile
•High degree of rotation/deflection
•Extremely strong

Cons
•Non-rebuildable
•Can have abbreviated life depending on use and element exposure
•Tend to transmit more vibration

Basic Bushings
Compound rubber or polyurethane bushings are the most widely used, cost-effective, and easy to come by. Since they are inexpensive and generally easy to replace, they tend to be a great joint for the entry- to midlevel wheeler. Since they are the least rigid, they tend to allow the joint and attached suspension link to rotate freely while helping to absorb vibrations transmitted from the wheel.

Companies such as Daystar Products (www.daystarweb.com) even offer upgraded versions of the composite-style bushings that replace your worn factory joints with more durable ones. Though both polyurethane and compound rubber joints are serviceable, most tend to see accelerated wear when frequently twisted off-road.

Pros
•Low cost
•Easily serviceable
•Absorbs vibration well
•Available in most parts stores
•More resistant to weather

Cons
•Less durable when used consistently off-road
•Can create a loose or sloppy feel in your suspension
•Not as strong compared to flex or Heim joints

Rebuildable Flex Joints
One of the most popular suspension joints in recent years has to be the re-buildable flex joint. These heavy-duty link ends are designed to offer the vibration resistance of a rubber or polyurethane bushing with the strength of a Heim. While each has its own way of securing inside the link end, most people choose to use a polyurethane insert for the spherical ball to rotate on. These joints are often forged and can range in price, quality, and longevity. Though we've had great luck with one of the original flex joints, Currie's Johnny Joint (www.currieenterprises.com), many aftermarket suspension companies have incorporated similar technology to create a wide variety of heavy-duty serviceable joints. For avid wheelers who still drive their vehicle a good amount on the street, flex joints are likely the best bang for the buck.

Pros
•Good vibration absorption
•Strong
•Easy to service
•Versatile

Cons
•Can be expensive
•The bodies tend to be large

Flexy Trails
For every wheeler who builds his own custom suspension system, there are probably 30 who don't. We mention this not to discourage you from building your own hot setup, but rather to assure you that the aftermarket understands this and generally has a variety of stages or levels of suspension to choose from.

For many companies these levels are separated by a range of parts, but often control arms and bushings are part of the upgrade package. Though you may be tempted to go with that full race setup, be sure to be honest with yourself and the suspension manufacturer. If you know that hardcore rockcrawling and desert racing are in your future, then the more heavy-duty Heim might be right for you. If a little puddle jumping or light trail wheeling is all that you foresee, you might find that a flex joint or even a basic bushing setup is all you really need.

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