Suspension Systems Tech Center

An introduction to the most misunderstood part of your vehicle: the suspension

Of course, many people are quite happy not knowing why it is that their vehicle can go over a speed bump without bottoming out. Sure, ignorance can be bliss, but knowledge is power. That's why AutoAnything is here to arm you with more suspension information than you can shake a dip stick at. First things first, we need to understand how your suspension system ties into your vehicle and how it works. Then, we'll investigate the good stuff: how to tweak and tune your suspension for improved handling, daring looks and extreme performance.

Your chassis, your suspension: an integral relationship

When we imagine an automobile, the first thing that pops into our minds is the body. After that, we probably think about the cockpit, the engine compartment and maybe even the chrome wheels. Hardly anyone would visualize a slip yoke eliminator, a pitman arm, a differential or a leaf spring. Why? The answer might be best summed up with an old cliché: out of sight, out of mind. There is a whole other dimension to our vehicles that mostly goes unnoticed because it is hidden away under a glitzy exterior. What's the name of this strange realm, you ask? It's called a chassis.

One of the toughest words to come out of France since laissez-faire, "chassis" literally means "frame," but it refers to more than just your vehicle's platform. The chassis is basically everything on your automobile from the ground up to the bottom of its body. An automotive chassis is made up of 4 components:

• Vehicle Frame: Like the DNA swimming around in our cells, the frame of any vehicle is its building block. It is the base on which every other critical part of the vehicle is anchored, including the engine, transmission, and even the body.
• Wheels and Tires: The all important link between the road and the automobile, wheels and tires make forward momentum possible. After energy and torque are created, it's up to the wheels and tires to create the traction needed to roll around.
• Steering Works: Energy without control is a recipe for disaster, especially when you're barreling down a windy mountain road at breakneck speeds. Everyone knows what a steering wheel is, but there's more to it than meets the eye. Deep down in the bowels of your chassis is an intricate weave of connecting arms and linkage that guides your wheels and keeps you in control.
• Suspension Systems: The part of your chassis that directly affects how your vehicle feels, the suspension is in charge of responding to road conditions. A suspension is the middleman between the road and you. The road dishes up rugged conditions, and your suspension transforms the bumps and dips into cloudlike smoothness (or stiff-as-a-board rigidity to suit the tastes of off-roaders).

A brief overview of the primary function of your suspension

Your suspension system basically has one very important job. It is in charge of controlling the ride of your vehicle. Now, ride means a lot of things to a lot of people. To a couple of preteens loitering around the front of their local strip mall, A ride is simply the parent who shows up to drive them home. Or, to an employee at Disneyland, a ride is the mechanical teacups that the kids love to twirl around in. However, to an auto enthusiast, ride is a vehicle's ability to create a comfortable feel while in motion. On freshly poured concrete and washboard paths alike, your suspension reacts to the situation and keeps your vehicle from rattling around like a Mexican jumping bean.

There are 2 tools that your suspension uses to smooth out your ride: springs and dampeners. Let's take a closer look at how these marvels of automotive engineering work.

Springs

Springs are your suspension system's first line of defense. As you drive over any surface, you will inevitably encounter bumps and dips. These variations in the surface of a street (or backcountry trail) send vertical energy through your wheels. Humps send your tires skyward, and holes draw them down. The spring's job is to absorb this energy and bring your wheels back to a state of equilibrium, which is when they are all at their standard height.

There are 3 basic type of springs used on modern automobiles: coil springs, leaf springs and torsion bars.

Coil Springs:

Like an industrial-grade Slinky, a coil spring is basically a heavy-duty strip of metal that has been wound around to form a spiral or helix. Coil springs are ideal for absorbing up-down energy, but their design does not deal well with side-to-side motion. As such, coils springs are typically found on all 4 wheels of most cars, and on the front suspensions of some trucks and SUVs. Eibach Pro Kit Springs are an excellent example of coil springs.

Leaf Springs:

Picture Robin Hood's trusty bow mounted to the underbelly of an automobile–that's basically what a leaf spring looks like. More specifically, a leaf spring is a stack of steel strips, called leaves. All the leaves are curved, and their arc flexes up and down when it goes over uneven paths. Leaf springs have a proven track record that spans all the way back to the medieval times, when they were used to support the axles of horse-drawn carriages and olde-time paddy wagons. Today, leaf springs are primarily used on rear-wheel drive automobiles, 4-wheel drive rigs, heavy-duty trucks, vans and SUVs. They do not deliver the same ride quality as coil springs, but leaf springs are more robust and handle weight better. A shining example of leaf springs: Skyjacker Softride Lifting Leaf Springs.

Torsion Bars:

Instead of flexing or compressing, a torsion bar absorbs energy by twisting. One end of the torsion bar is fixed firmly to a vehicle's frame, and the other side links to the vehicle's control arm. When the auto runs across a rough patch of road, the up-down energy flows into the torsion bar, which then twists. Because only the one side is mounted firm, the torsion bar will only rotate so far before it spins back in the opposite direction. Torsion bars are primarily used on front-end suspensions, and are found on all types of automobiles. Rancho Torsion Bars represent a solid set of replacement bars for vehicles with this suspension type.

Dampeners

As Newton's 3rd Law of Motion states, for every action there is an equal and opposite reaction. When a suspension spring takes in upward energy, it has to release it as a downward force. However, that downward momentum then causes the spring to bounce back upward. This back and forth resonance, or jounce to engineers, would go on for miles if not for another key suspension component: dampeners (aka shock absorbers).

Just as Penn would have a dull Vegas act without Teller, a spring would not improve your ride unless teamed up with a shock. It's the shock's job to make the energy from your springs soft and as bounce-free as possible. Imagine dropping a basketball off the roof of your house. If it falls onto concrete, it will bounce back up and dribble down the driveway. On the other hand, if it falls onto a pile of pillows or leaves, then it will just stop and wait for you. In a nutshell, that's what a shock does.

A guide to the different types of suspensions

Different vehicles are deigned and built to do different things. A sporty little roadster and a behemoth dually pickup would not roll around on the same chassis, and they certainly would not use the same suspension type. As you would expect, there are a number of suspensions rolling around all over, from the traffic nightmares of Los Angeles to the wide-open routes of the Gobi Desert.

There are 2 basic types of suspension systems: dependent and independent. Let's take a closer look at the unique characteristics of each system.

Learning about dependent suspension systems

On a dependent suspension system, the wheels on the left and right side of the vehicle are connected and work together. Generally, the dependent suspension uses a solid axle that spans across the entire width of your frame. Because both wheels are linked to this single beam, they respond to road conditions as a pair. If the camber of one wheel bends outward, then the other wheel follows suit.

On uneven terrain, dependent suspension systems function a lot like a seesaw. When one side dips into a pothole or rises over a rock, the other side goes in the opposite direction, either up or down. Needless to say, this bucking energy can be about as comfortable as riding a mechanical bull. However, with modern shock absorbers and springs, dependent suspension systems can be quite comfortable off-road and on.

Because of their ruggedness, dependent suspensions are often used on heavy-duty trucks, SUVs and rear-wheel drive cars. They also find there way onto some front-wheel drive autos. But, most new cars have some form of independent rear suspension system for greater ride comfort. Besides, most people wouldn't drive Saturn, BMW or Hyundai sedans on dirt roads except in the rare event that they find themselves in the starring role as fleeing bandit in an episode of COPS: On Location in Las Vegas.

Independent Suspension System

As the name implies, an independent suspension system does not use a single axle to connect both sides of the vehicle. Instead, the wheels on an independent suspension system react separately to road conditions. Bumps and basins on the passenger's side do not cause the driver's side wheels to rise or fall.

Independent suspension systems are rapidly becoming the standard for automobiles, and some SUVs and trucks too are using this engineering. They provide superior ride quality but are more expensive and time-consuming to manufacturer than dependent suspension systems.

The guide to lift kits

Traffic jams. Nothing makes your gas-pedal foot itch more than spending a claustrophobic afternoon in bumper to bumper gridlock. When the weekend rolls around, civilization is the last thing on your mind. You need an escape. With a lift kit, you can hightail it away from the urban jungle and stretch your rig's legs on the backcountry roads where minivans and sports compacts fear to tread.

Lift kits give you the unbridled freedom to tackle almost any terrain, but that's not all. Boosting the height of your vehicle also enhances its image. Tall trucks and giant SUVs command the respect of the road. Their towering stature adds a daring edge that stands out from the other models on the road. Part utility and part aesthetic–lift kits have something for everyone.

Your new lift kit will:

• Boost and bolster your suspension for tremendous off-roading potential
• Amplify your vehicle's daring look
• Make room for those stylish, oversized wheels and tires you've always wanted
• Level out that forward rake on heavy-duty trucks

Boost and bolster basics:

No matter how far up the evolutionary ladder humans climb, the call of the great outdoors still draws us away from the bright lights and bustle of city dwelling. Sometimes, we just need to be around dirt. Some people cop their mud fix by taking up gardening while others turn to camping. The more adventurous among us feed this primal urge by veering off the beaten path and conquering an untamed stretch of gravely, rocky, boggy terrain.

Unfortunately, trucks and SUVs tend not to come from the factory equipped to handle the harsh conditions of spirited off-roading. That's what lift kits are for. First and foremost, they boost your vehicle's ground clearance. That way, you can drive over uneven, rock-strewn paths without pummeling your undercarriage on boulders and tree stumps.

Second, lift kits increase your suspension travel, which is a fancy term for the distance that the moving parts on your suspension can travel away from the fixed parts. In other words, the limit on how far your wheels, springs and shocks can move up and down. The greater your suspension travel, the deeper the holes you can plow across and the taller the boulders you can climb over.

Lastly, a lift kit bolsters your suspension so that it can survive the rigors of unpaved expeditions. Burly shock absorbers, rugged steering linkage and massive springs are just a few of the heavy-duty components in a lift kit that strengthen and fortify your suspension. That way, you can barge over unforgiving topography without worrying about puncturing your oil sump every time you charge over a fallen log or launch off the golden crest of a desert dune.

Awe inspiring style advice

There are a lot of trucks and SUVs put-putting around in big metropolises and sparse rural hamlets, and for good reason. Besides their incredible handiness (you can't squeeze a 62" HDTV or a palm tree sapling in the trunk of any Daewoo), trucks and SUVs offer extra safety, spacious interiors and sharp looks.

However, with everyone running out to pick up Detroit and Japan's latest 4-wheel behemoths, we can sometimes feel like some anonymous member of the herd. Sure, there are ways to stand out from the pack with flashy chrome accents, but nothing compares to the bold statement of a lift kit. Those extra inches transform your vehicle into a commanding presence. And, you can leverage this forceful look to lord over the highways, byways and city streets—you'd be surprised to see just how fast that absentminded slowpoke in the fast lane will scoot over when he sees your lifted rig pull up behind him. Plus, it's nearly impossible to get lost searching for your lifted vehicle in a crowded parking lot–just look up!

The eye-catching wheels and tires primer

Let's be brutally honest—stock wheels tend to be bland, and factory tire sizes can look dwarfish on trucks and SUVs. Unfortunately, you cannot just pick up a set of huge 20" rims with 36" mud bogger tires and expect them to fit onto an unlifted vehicle. There simply isn't enough room in the wheel well without a lift kit.

Now, you don't need to go sky high in order to make room for your dream dubs. In most instances, a simple 2" lift kit is all it takes to make the clearance for big and tall tires. However, there still may be some rubbing along the rim of the wheel well at full shock compression. If this is a problem, the easy solution is to do some minor trimming and add some fender flares.

Techniques for leveling a raked rig

Rakes! They're great for gathering leaves and for spoiling a pickup's sleek profile. Unfortunately, most ½-ton, ¾-ton and full-ton trucks come from the factory with this goofy, forward-slanted design. From the side, they look like some invisible giant is resting all his weight on the front bumper. To the credit of auto manufacturers, there is a legitimate reason for it. These pickups are made for hauling heavy loads. If you pack a ton of concrete into the bed, that weight causes the rear to sag down to the same height as the front. So, they hoist the tail to compensate for the rare event when you have to haul your life-size, bronze memorial statue to ol' number 3, Dale Earnhardt.

However, most of us never use our full payload capacity, so we're stuck with this odd rake-forward look. Even worse, this height difference can make cornering a nightmare because the bed wants to fishtail. Correcting this imbalance is simple: lift the front-end with a custom leveling kit. The 2"-3" of front-end boost in a leveling kit is usually enough to right the scales and accomodate larger wheels and tires.

How does a lift kit work anyhow?

A wise man once sang that there are different strokes for different folks, and the same can be said for lift kits. Ford, GM and Nissan do not share chassis blueprints with each other, so they all design suspensions that are unique from the rest. As you would expect, there are diverse and sundry ways to jack up these numerous suspensions. Let's take a closer look into the most common lift styles for the rear and front.

Rear lift kits

Boosting the backside of trucks and SUVs is fairly straightforward because most of these rigs have dependent rear suspensions. Here are the most frequently used techniques:

Blocks:

A vertically challenged motorist might tie boxes to his shoes to reach the pedals. Likewise, an undersized vehicle can easily add a couple of inches with a set of blocks. These spacers fit in between the rear coil spring and axle for a fast height hike that does not affect stock ride quality.

Add-A-Leaf:

As their name implies, add-a-leaf lifts raise your vehicle up by stacking extra leafs into your leaf spring packs. Just like the blocks, add-a-leaf lifts are straightforward to install and should not cause a noticeable change in ride or handling.

Full Spring Replacements:

Blocks and add-a-leaf springs are usually used for mild lifts. When you want to reach nosebleed heights, then you'll need a whole new set of springs. Of course, the great thing about full spring replacements is that they correct handling problems caused by worn out stock parts.

Front lift kits

Front-end suspensions tend to be more complicated than the rear because of all the extra steering linkage. Some of the lifting methods remain the same, but there are some newfangled systems as well. Let's go in for a closer look:

Spacers:

Front coil springs and struts are becoming increasingly popular on trucks and SUVs, and they can be lifted with spacers the same as rear springs are raised with blocks. The spacers sit on top or below your front springs to add a couple inches without dramatically altering your stock ride characteristics.

Add-A-Leaf:

Many heavy-duty rigs have the same type of springs up front as they have in back, and they can be lifted the same way. Stack a few extra leaves onto your leaf spring pack with add-a-leafs, and you'll be riding high in no time.

Steering Knuckles:

Almost as important as brakes, your steering knuckles are the pivot point that turns yours wheels and lets you steer. Lift kits use taller steering knuckles to send your rig soaring upwards. This type of lift is usually used on vehicles with torsion bar springs.

Spindles:

Just like steering knuckles, spindles play a vital role in the height of your vehicle. Swapping out your old gear with new spindles works the same as installing off-road steering knuckles. They are taller than stock, which pushes your vehicle up higher.

Control Arms:

Otherwise known as a wishbones or A-arms, the control arms are the all important connector between the wheel hub and the frame. Unlike steering knuckles and spindles, aftermarket lift control arms are not taller—they're shorter! This creates the same type of gap between the frame and wheels as before, but in a different location. Often, altering the control arm requires a new set of coil springs to compensate for the new elevation, but that's what you expect from a lift: newer, tougher parts.

A few words of advice about choosing a lift kit

Now that you know just about all there is to know about the benefits of lift kits and how they work, all that's left to do is pick the right one. For a greenhorn suspension tinkerer, this may seem easier said than done. But, it really is not as difficult as it sounds. Just ask yourself these vital questions:

• Which lift height is right for me?
• Can I install my own lift kit?
• Do I need anything else besides the lift kit?
• Are lift kits legal?

Which lift height is right for me?

There's a big difference between a 2" bump and a full-blown 8" hike. Because lift kits involve such an extensive installation, you want to get it right the first time. Not too tall that you scrape your roof against your garage door; not too short that you maul your chassis the first minute you pull off the pavement. Here are a few pointers to consider before selecting a lift kit:

• For dedicated off-roaders, bigger is generally better. If you plan on wandering through uncharted passages, you need to be prepared for whatever lies ahead (and behind) of you. Depending on the limitations of your stock suspension, 6"–8" is a good lift kit size. It will give you good ground clearance while allowing plenty of room for oversized tires. Of course, if you want to tackle a Rubicon-grade trail, a 10" lift may be right up your alley.
• For the occasional off-roader who does not want to lose the factory-feel, a more subdued lift kit would be better. 2"–4" is a good height boost for retaining comfortable handling while still giving you the clearance to head out onto unexplored routes.
• For a more aggressive rig that may or may not leave the pavement, get a lift kit size that matches how tough you want to look. A slight lift of 2"–4" will certainly give your vehicle a powerful profile, but a 6"–8" lift will make you king of the road. Or, you can even go monster-size with a gigantic 10" boost for complete dominance.

Can I install my own lift kit?

Mounting a lift kit is a lot more involved than bolting on a new cat-back exhaust system or a cold air intake kit. You'll need more than just some screwdrivers and ratchets to get this job done. Some lift kits require you to get medieval and break out the pliers, blowtorch, power drill and Sawzall.

AutoAnything recommends that you have your lift kit installed at a professional shop. Usually, the best place is your local off-road specialty garage because they should have plenty of experience doing the work. However, if you have the tools, know-how and time, then you can do the job yourself. A well seasoned wrench wrangler can finish a full 4-wheel lift in a day or 3.

Do I need anything else besides the lift kit?

Lifting your vehicle with a lift kit can have a dramatic impact on its driving dynamics. Beyond the ride quality and handling, the shift in height can have more practical effects as well, such as just getting in and out of your rig. Here is a short list of accessories to compliment your lift:

Steering Stabilizers:

Big lifts and big tires lead to big-time wheel shimmy and wandering problems. Moreover, rough roads often cause another obnoxious issue: wheel kick. Steering stabilizers solve all three problems. These horizontal shocks smooth out your handling and even add an imposing look to your front-end.

Performance Programmers:

Many people think that performance programmers are only used to unleash your engine's hidden horsepower and torque. While this is their primary job, performance programmers also have another important function: speedometer recalibration. Installing bigger tires or a different rear-end gear set throws your speedometer out of whack, which can lead to a ticket and a day in traffic court. A performance programmer recalibrates your engine's speed sensor to give you an accurate readout of your velocity. Check out our Performance Programmer Research Guide for more details.

Multi-Shock Kits:

Rugged outdoor treks put a lot of stress on your suspension. If you plan on doing some serious off-roading, you need more than just 1 shock in each corner of your vehicle. With a multi-shock kit, you can mount extra shocks up front for greater dampening, less body roll, more stability and an aggressive look.

Nerf Bars & Side Steps:

Stepping up into a lifted rig can be quite a chore, especially for young and old passengers. Like a built-in ladder, nerf bars and side steps help hoist you up and down from your cabin. Learn more by leafing through our Nerf Bar & Side Step Research Guide.

Skid Plates:

Gaining ground clearance is one of the biggest benefits of a lift kit. But, even the tallest trucks and SUVs are vulnerable to damage down below. Like body armor for your underbelly, skid plates protect your powertrain and suspension components from scrapes, dents and gouges.

Big Brake Kits:

Stock rotors and pads are designed to work with factory-installed wheels. Upsizing your rims and tires adds weight, which in turn increases the time and distance it takes to stop. Larger rotors boost your braking leverage for faster, shorter, safer stops. Plus, they look amazing riding behind open-spoke rims.