Custom Suspensions

 
 

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

 

Some things in life just sound too complicated to wrap our brains around. Quantum physics, Federal Reserve monetary policy and brain surgery are all fields that leave students and adults alike scratching their heads in bewilderment. All too often, the inner workings of an automobile's suspension gets lumped alongside these enigmatic subjects. Even seasoned gear heads, who can blueprint an engine without so much as breaking a sweat, get weak in the knees around torsion bars and steering knuckles.

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 1 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.
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.
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.

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.

Reprinted from: http://www.autoanything.com/suspension-systems/50A26A163A1.aspx