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Suspension Dictionary

Posted in How To: Suspension Brakes on February 1, 2013 Comment (0)
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The theme of this issue is suspension systems, so we thought it would be appropriate to create a list of major, commonly used suspension components, define what they do, and address some things that can go wrong with each.

For those of you that are newbies to four-wheeling, you’ll soon learn that much of the mechanical action of interest takes place underneath your rig. That’s where the magic happens, whether its lockers, axleshafts, and yes, the suspension. For this reason it’s a good idea to know what the major suspension components are, what they do, and what can go wrong with said item. In the end, the understanding of how your suspension works will help you choose what mods you need to make and even what spare parts you may need to carry. Oh, and you’ll be able to join in on the suspension conversation around the campfire.

A-arm
What it does: A pair of these (an upper and a lower) are typically found on each side of an independent front suspension (IFS) and independent rear suspension (IRS). The inside of these arms attach to the vehicle’s frame and pivot up and down via bushings. The outside of these arms are fitted with ball joints that allow the attached knuckles to pivot with steering input. Typically, most A-arms are made from steel, though aluminum is sometimes used.

What can go wrong: Short of a collision, A-arms hold up pretty well and it’s usually the ball joints that fail in the event of a gnarly tire-to-obstacle impact. It’s rare, but the stock rubber bushings can wear out, which can affect the alignment and overall drivability. Aftermarket A-arms often use polyurethane bushings, which require regular lubrication. Shown here is a stock GM A-arm (left) next to an upgraded Rough Country (www.roughcountry.com) A-arm, which features beefier construction and larger, greasable ball joints.

Airbag
What it does: Sometimes called an air spring, this air-filled device can be used instead of a standard suspension spring to offer a range of adjustability. Geby Wager’s Top Truck Champions’ Challenge rig is an example of an airbag-equipped machine. The current Ram 1500 is an example of a vehicle that is available from the factory with airbags in the front and rear suspension. These types of airbags are designed to compensate for heavy loads like towing or hauling, automatically. They can also be used to increase the vehicle’s ride height to improve off-road performance. Several aftermarket companies like Firestone (www.firestoneindustrial.com) offer airbag kits that supplement leaf springs for hauling or towing (shown). Air Lift (www.airliftcompany.com) is one of the companies that offer air springs that fit inside coil springs to help handle heavy loads. Some of these airbags require the use of a compressor and auxiliary air tank, while others can be filled manually via a Schrader valve. They work great for leveling a vehicle used for towing and hauling and they can also add stability.

What can go wrong: Over time airbags can dry rot, leak, or suffer a puncture. Airbags require the use of air lines, which can leak or break. Control units and compressors can also fail. In rust-prone environments, the steel end-caps found on some airbags can rust and fail. It’s also worth noting that more pressure in the bags equals a stiffer ride and less wheel uptravel.

Ball Joint
What it does: Ball joints are basically spherical bearings that fasten the knuckle to the A-arm or “C” on a solid axle and allow the steering knuckle to pivot, which allows you to steer your vehicle. Most modern 4x4s have upper and lower ball joints on each knuckle. So what do ball joints have to do with suspension? Well, in a solid axle application ball joints have nothing to do with the suspension, but in an IFS suspension the ball joints have the additional duty of moving in a vertical plane with the A-arms.

What can go wrong: It’s worth noting that adding larger/heavier wheels and tires and increased wheel backspacing can cause ball joints to wear at a much faster rate than normal in both solid axle and IFS applications. If ball joints are worn the result may be steering wander and/or clunking. If the ball joints fail, the knuckle can even detach. There are heavy-duty ball joints available for some applications from companies like Dynatrac (www.dynatrac.com) and Omix-Ada (www.omixada.com). In an IFS application the ball joints can be a limiting factor in regards to suspension travel because their range of motion is designed for stock wheeltravel. Long-travel IFS suspension systems often include A-arms that are fitted with replaceable uniball bearings that have an increased range of motion and are heavier-duty than a standard ball joint. Camburg Engineering (www.camburg.com) is one of those companies that offer such a joint.

Bumpstop
What it does: A bumpstop cushions the last few inches of suspension uptravel, eliminating a harsh “bottoming out” event where the suspension can slam into the vehicle frame or unibody. Bumpstops are typically made of rubber, though the aftermarket often replaces them with polyurethane. When a vehicle is lifted, a longer bumpstop or a lowering bracket needs to be installed to ensure that the suspension’s final uptravel is cushioned correctly.

What can go wrong: Bumpstops that are well used or old can crack or break. They can even just fall out in the case of OE-style push-fit bumpstops. Oil leaks can cause rubber bushings to soften and become ineffective. It’s important to replace a damaged or missing bumpstop immediately to ensure that the suspension isn’t damaged during full compression. There are many sources for bumpstops from suspension companies including Skyjacker (www.skyjacker.com), BDS Suspension (www.bds-suspension.com), and Rancho (www.gorancho.com). Hydraulic bumpstops, like the adjustable and rebuildable JounceShock from Light Racing (www.lightracing.com) are the pinnacle of bumpstop performance and are basically small shock absorbers that gradually damp the last few inches of uptravel.

Bushing
What it does: Bushings made of rubber or polyurethane are the most common bushings found at pivot points in a suspension. For example, where the IFS A-arms mount to the vehicle frame, where the leaf springs mount to the shackles and hangers, and in the ends of link arms. Basically, the bushings allow the component to move in a pivoting motion without allowing side-to-side movement. Shown here is a metal sleeve being inserted in a large polyurethane bushing in a link-arm assembly.

What can go wrong: Rubber bushings typically hold up well, but will dry out and crack with age. An engine oil leak can saturate the rubber, causing it to soften and fail in short order. Heat is also a bushings enemy. If a bushing does fail, you’ll know it because whatever component they’re in will usually move in ways they’re not designed to and make noise and/or affect drivability. Aftermarket polyurethane bushings like those available from Daystar (www.daystarweb.com) are impervious to oil, but they’re harder than rubber and they need to be lubricated regularly.

Coilover
What it does: Instead of utilizing a separate coil spring and shock, a coilover shock is both of those items constructed as a unit with the coil spring mounted onto the shock. This setup combines ride height and damping in one package. A coil-on-shock strut, as found on many late-model ½-ton IFS pickups, is similar to a coilover, but struts don’t offer the height, compression, and rebound adjustment of a coilover. Fox (www.foxracingshox.com) is one of the companies that offer coilovers with an external shock reservoir to improve cooling and wheeltravel. Shown here is a Skyjacker (www.skyjacker.com) coilover shock assembly on a Toyota Tacoma pickup.

What can go wrong: A coilover can wear out over time, but the beauty is that they’re rebuildable. Typically a strut is disposed of and replaced. If you live in a salt-prone environment the coilovers threaded adjusting mechanism can rust and become inoperable.

Coil Spring
What it does: The coil springs under a typical 4x4 are designed to set the ride height of the vehicle as well as have a rate that isn’t too hard or too soft. Vehicles that carry heavy loads typically have a higher spring rate. Some coilover shocks use two or even three coil springs of different rates and sizes to enhance the performance of the suspension. Some suspension systems set the coil spring by itself, some place it over the shock absorber, and some connect it to a shock (a coilover).

What can go wrong: As a vehicle ages the coil springs can sag. This allows the vehicle to ride lower to the ground, which decreases the amount of usable suspension compression. A heavy winch and bumper or snowplow can hasten coil spring sag. Installing an adjustable airbag like those from Air Lift (www.airliftcompany.com) to help support the extra weight and decrease the stress on the spring, may lead to longer life, but can limit the travel of the suspension. We’ve had numerous coil springs crack and break from just normal use and age, necessitating a replacement. Sometimes we’ve used OE replacements, while other times we’ve used the broken spring as an excuse to install a lift kit.

Leaf Spring
What it does: A leaf spring, like a coil spring, is designed to set the ride height of the vehicle and it’s designed with a specific rate to ensure that the ride isn’t too soft or hard. Also like a coil spring, a leaf spring found in vehicles that carry heavy loads have higher spring rates. Variations found within the leaf-spring family include elliptic, semi-elliptic, three-quarter-elliptic, and quarter-elliptic. A leaf spring has a trait that a coil spring doesn’t have, in that it also locates the axle without the need for link arms.

What can go wrong: Leaf springs can crack from being overloaded, overextended, overcompressed, or simply due to age. When they crack it can cause the vehicle to lean, the axle can be out of center, or they may generate noise. The spring eyes (the circular part at each end of the spring where a bolt passes through the bushing to connect the spring to the hanger or shackle) can also break, which can cause the spring to lose its ability to lift the vehicle and keep the axle from shifting side-to-side. Sometimes the OE center pins can fail, which can cause the axle to shift. It’s a good idea to upgrade the center pin to a higher grade bolt if you’re experiencing this problem. Sagging leaf springs should be replaced and there are many companies that offer complete replacement springs, including Deaver Spring (www.deaverspring.com).

Leaf-Spring Shackle
What it does: As a leaf spring flexes, its length eye-to-eye changes. Since a leaf spring is affixed to a solid hanger at one end, a shackle is located at the other end between the leaf spring and the vehicle frame to allow for movement. Bushings, rubber in OE applications and polyurethane in most aftermarket applications, are also used to allow the shackle to pivot. The shackle shown here is on a rear leaf spring of an ’05 Dodge Power Wagon.

What can go wrong: Like anything else, smashing the shackle into an object on the trail can damage it. If you live in a rust-prone area, shackles can corrode. The bushings used in the shackles can also wear. Summit Racing (www.summitracing.com) has a wide variety of stock and longer replacement shackles. Installing a longer shackle is an inexpensive way to get some lift, but doing this has downsides including an increase in pinion angle, a decrease in approach/departure angle, and if a really tall shackle is used, added side-to-side stress on the shackle hanger and spring eye.

Leaf-Spring Shackle Hanger/Leaf-Spring Hanger
What it does: Hangers are used to mount the leaf spring to the vehicle. Usually one end of the leaf spring is mounted directly to the hanger (this is called a spring hanger) while on the other end the shackle mounts to the hanger (this is called a shackle hanger). Hangers may be a small part physically, but since they are the mounting point for the leaf springs they play a big role. The leaf-spring hanger shown here is on a Dodge 2500 pickup.

What can go wrong: Hangers can eventually corrode due to road salt or age. If this happens, the leaf spring or shackle will lose its mounting point, which can result with the frame of the rig dropping onto the axle. Damage can also occur from contact with an object on the trail or even contact of the leaf spring to an obstacle, which can transfer the shock to the hanger. One of the many sources for new spring and shackle hangers is 4Wheel Parts (www.4wheelparts.com).

Lift Block
What it does: Lift blocks are often found in leaf-spring rear suspension systems. They are located between the axle and the leaf spring pack. Lift blocks have a hole in the bottom that receives the leaf-spring center pin or pins. Many OE 4x4s come with blocks from the factory, though some may use thin stacked pieces of metal (sometimes called a mini spring pack), as shown in this photo of a ’05 Dodge Power Wagon. Many aftermarket leaf-spring lift kits include taller lift blocks to raise the rear of the vehicle.

What can go wrong: Over time the U-bolts that connect the axle to the leaf spring can loosen, causing the block to crack or wear out the holes in the block. If a block fails, the result can be devastating to the rear suspension and/or axle. It’s never a good idea to stack lift blocks due to the potential for them to collapse if the U-bolts become even slightly loose. Lift blocks should never be used on the front axle due to the potential for failure resulting in a loss of steering control. Taller blocks enhance axlewrap and the longer U-bolts needed for the taller blocks can stretch and loosen up, so it’s a good idea to forego lift blocks and get new springs if you want lots of lift. Another lift option is a shackle flip kit, like the Offroad Design (www.offroaddesign.com) kit that’s available for 1967-and-up GM trucks. This kit includes brackets that allow the shackles to be flipped to create 2½ or 4 inches of lift without using lift blocks.

Limiting Strap
What it does: Overextending a suspension can be hard on parts. Depending on the suspension type, overextension can have several side effects from simply unseating the coil springs to damage of the ball joints, shocks, and tie-rod ends. It can even cause driveshaft overextension and/or bind. A limiting strap is designed to halt downtravel. Most limiting straps are made from nylon and include mounting buckles at each end. A strap is typically placed at each wheel, but sometimes a strap is placed in the middle of a solid axle setup to deter driveshaft separation. There are many sources for limiting straps including Off Road Warehouse (www.offroadwarehouse.com). This photo shows a limiting strap mounted on Jeremy Naeger’s Top Truck Challenge-winning buggy.

What can go wrong: It’s important to get the right length of limiting strap. If the strap is too short it’ll impede your vehicles suspension downtravel. If it’s too long it’ll be worthless. Limiting straps can be damaged by trail debris or obstacles or if they get pinched between components, so it’s good to inspect them often. Also make sure that your mounting points are strong.

Link Arm
What it does: Also called control arms, they’re used on solid axle setups. Link arms locate the axle longitudinally under the vehicle. Without link arms the axles would be free to move fore and aft. There are a number of variations of linked suspensions, but most stock 4x4s use a four-link arrangement with a track bar, meaning there are two upper links and two lower links locating the axle front to back, with the track bar controlling the side-to-side movement of the axle. One end of each arm connects to a bracket on the axle and the other end connects to a bracket on the vehicle frame or unibody. Shown here is the passenger-side lower link on a ’05 Dodge Power Wagon. Because the links must cycle with the axle, both ends in this application use flexible rubber bushings, but aftermarket links often use a rubber or polyurethane bushing on one end and a flex joint or rod end on the other to help increase their flexibility. Most aftermarket links are made from material that is beefier than stock and many are adjustable for alignment purposes.

What can go wrong: Road salt can do a number on factory links and their mounts. Bushings can fail due to age, heat, or oil. Some factory links are made from thin-walled material that can bend easily. If lower links come in contact with trail obstacles, they can be damaged. An example is the Toyota FJ Cruiser, which has weak rear stock lower links. All-Pro Off-Road (www.allprooffroad.com) offers its beefy Ultimate Lower Links for the FJ, which are not only strong, but include a Currie Johnny Joint on one end and a polyurethane bushing on the other to enhance suspension articulation. Chances are that there’s an aftermarket company that offers beefier links for your rig.

Rod End
What it does: Due to their high degree of rotation, spherical rod ends are often used on link ends and track bars in suspension systems that are designed for above average suspension articulation. There are a wide range of strengths and sizes available. The Ballistic Fabrication (www.ballisticfabrication.com) rod ends shown here are on Dustin Chernoh’s heavily modified ’83 Jeep CJ-8 Scrambler that we featured in the March 2011 issue of Four Wheeler.

What can go wrong: Spherical rod ends are not rebuildable and they do wear out, so it’s best to carry spares. They also transmit shock and vibration more than a rubber, polyurethane, or flex joint, so they may not be the best choice for a daily driver.

Shock Absorber
What it does: Shock absorbers control the rate of suspension movement in response to bumps. They also help to reduce roll and sway when accelerating, cornering, or braking. Without shocks, your rig would bounce after driving over uneven terrain until the energy was dissipated from the springs. There are a number of types of shocks, and some, like race-ready multi-tube bypass shocks and MetalCloak’s 6Pak shocks (www.metalcloak.com) are high-tech units that feature mega-adjustability and/or long-travel. Most 4x4s are fitted with monotube or twin-tube units. Pictured here is one of the Bilstein 5160 (www.bilsteinus.com) remote-reservoir shocks installed on our Dodge Power Wagon.

What can go wrong: Like any mechanical part, a shock can wear out with age. Sometimes the shock shaft will become pitted causing a leak, while other times it could be overheating, poor suspension geometry, or trail damage (like a bent shaft or damaged body) that will kill it. When most shocks wear out they are just disposed of. Basic shocks can’t handle being cycled for long periods of time over rough terrain. When this happens the oil inside the shock foams and the performance of the shock dwindles. This is why many wheelers choose to run race-style reservoir shocks. These shocks have an external reservoir and this configuration allows the shock to run cooler. An added benefit is that many of these types of shocks are rebuildable. Long-travel shocks are used in conjunction with long-travel suspension systems to maximize wheeltravel. Sometimes the failure isn’t the shock, but rather the shock mounts. The mounts can be damaged by an improper length shock, poor grade hardware, overextension of the suspension, or a missing bumpstop. If a shock mount breaks, the result will be a non-functional shock that will flop around on the other mount possibly causing damage to the remaining mount or the rig.

Suspension Joint
What it does: These rebuildable joints, often called flex joints, are typically used on the ends of link arms. They offer a good range of motion so they work well with flexy suspensions and they isolate shock and vibration well so they’re daily driver-friendly. An example of a rebuildable suspension joint is the Rough Country X-Flex Joint (www.roughcountry.com), shown here.

What can go wrong: Typically, these joints need to be maintained (greased) often, so if you have to factor that into your maintenance routine. And they will wear faster than a rubber or polyurethane bushing, so plan on rebuilding them every so often.

Sway Bar
What it does: A sway bar helps to control body roll, thus making your rig handle better. It does this by connecting a metal bar to each side of the suspension. This bar distributes the force from one side of the body to the other.

What can go wrong: By its very design the sway bar inhibits suspension travel. This is why the off-road aftermarket has created sway bar disconnects, which allow the sway bar to be detached from the suspension off-road so the travel can increase. There are many disconnects available and include those from JKS (www.jksmfg.com) and TeraFlex (www.teraflex.biz). Not only does a sway bar impede travel, we’ve seen sway bar end links break during wheeling where the suspension was cycled to its maximum. Manufacturers such as Dodge/Ram and Jeep have devised ways to detach the sway bar from inside the cab. Our ’05 Dodge Power Wagon has a pushbutton-operated sway bar disconnect (pictured) that disengages the sway bar and allows the suspension to flex to its fullest.

Torque Arm
What it does: Also called a traction bar or anti-wrap bar, this component helps combat axlewrap in leaf spring-equipped rigs. Axlewrap can happen during maneuvers such as hard acceleration or climbing a steep obstacle. What is happening is that the leaf springs are contorting into an “S” shape, and typically the result is that the axle moves up and down rapidly as the leaf springs twist and recoil in an attempt to maintain their intended shape. This is hard on the springs as well as the rear drivetrain. A torque arm has one end mounted to the axle and another to the frame and is designed to keep axlewrap from happening.

What can go wrong: A torque arm can impede suspension travel. Arms designed specifically for off-road travel will include a flexy joint or rod end so it flexes along with the suspension. Some torque arms hang low and can decrease ground clearance. If your rig sees a lot of off-road time, a system like WFO Concepts (www.wfoconcepts.com) universal torque arm is worth a look because it’s designed to mount high and it comes equipped with high-quality QA1 rod ends.

Torsion Bar
What it does: Some IFS rigs are equipped with a torsion bar setup. Instead of using coil springs in some configurations, this system uses long steel bars that act as “springs.” The torsion bars typically slide into slots in the lower A-arms and into “keys” in a crossmember amidships. As the A-arms travel up and down this causes the bar to twist on its axis, which is resisted by the bars torsion resistance, hence a spring effect. In this photo you can see the lack of springs and the driver-side torsion bar is visible.

What can go wrong: Like any other spring, torsion bars can fatigue over time, especially if heavy components like a winch/bumper or plow is fastened to the front of the truck. In salty environments the torsion bars will rust to the control arms and keys, making removal very difficult. Some suspension lifts use crossmember drop brackets to keep the torsion bars properly aligned with the front suspension, but the downside to this is a loss of ground clearance. Finally, adjusting the stock torsion bar keys to create suspension lift decreases the amount of suspension downtravel.

Track Bar
What it does: Found mostly on coil-sprung, but also some leaf sprung, solid axle-equipped rigs, the track bar (also known as a panhard bar) locates the axle laterally. It allows the axle to travel up and down, but prohibits it from traveling from left to right. The track bar fastens to the vehicle frame on one end and to the axle on the other. When a rig is lifted, many aftermarket suspension companies include a track bar drop bracket to correct the track bar angle. Typically, an OE track bar will be fitted with a rubber bushing on at least one end. The track bar shown here is on a Dodge 2500 pickup truck.

What can go wrong: The rubber bushings can wear out over time, causing steering “slop.” Also, the factory track bar can limit wheeltravel. There are many aftermarket track bars available and most are beefier than stock and some are fitted with rod ends to improve suspension articulation. An example of a beefy, rod end-equipped track bar is the KORE Off-Road 3rd Gen track bar (www.koreraceshop.com) for 2003 through 2012 Dodge/Ram trucks.

U-bolt
What it does: There are typically two U-bolts used per side on a leaf spring-equipped, solid axle rig. The U-bolts provide the necessary force to clamp the axle, leaf springs, and lift blocks (if equipped) together.

What can go wrong: If U-bolts become loose the axle may shift, the ride height may change, or the axle pinion angle may change, resulting in driveshaft vibrations. In a worse case scenario there can be significant damage to the suspension and axle. Corrosion may also be a factor in salty environments. Regularly inspect and tighten the U-bolts, especially if you have added a lift and installed new U-bolts.

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