Suspension Basics

Different adjustments of suspension. alignments are one of the largest factors in the way a car handles. LARGEST. not your strut bar, not your bling bling 20's.

Camber - negative and postive are what we got here. lets use a diagram.this is your car |xxx| from behind. zero camber good?
this is negative camber /xxx\ wheels pointed inward
get it now, postive \xxx/ wheels pointed out
now as you turn, the car rolls (tilts) as it rolls you move the tires contact patch changes. the tire is no longer even with the pavement, to counteract this, you dial in camber. so as the car rolls, it rolls onto the largest area of contact patch. downside of this is, when you're not turning, you're riding on the inner edge of the tire, not optimal for acceleration or braking traction, as well as wearing the inner edges of the tire quicker. make a choice.

Caster- imagine your suspension in the front, hub at the bottom, strut mounts on top. positive caster is when the top of the struts point toward the rear of the car. caster is what allows the wheels to straighten out when you let go off the wheel. for performance, try and get as much caster adjustment allows, which isnt really very much.

Toe- imagine you superman floating above your car looking straight down on you car. the wheels are like this in the front |xxx| that is zero toe. /xxx\ is toe in, \xxx/ is toe out. toe in makes the car more stable in a straight line and is easier on the tires. toe out makes the car turn in more crisply, while making straight line stability a bit tricky, and wearing tires fast. toe, out of all adjustments, is what will kill tires the quickest out of all adjustments.

got that all? great. now some talk about the design of suspension itself, this will mainly pertain to imports, so no DeDion links or crazy rocker armed setups

Macpherson strut design - one of the simplest front end designs. found in cars like the Toyota Celica, dodge neon and the newest generation of civics. basically a single a arm at the bottom, and a strut/spring combo linking the whole shebang to the strut top mount, maybe a few rods thrown in to help stiffen up the multiple angles of loads that are applied. simple, effective and cheap. when mac struts are used in the rear, it is often referred to as a chapman strut, after the lotus designer colin chapman.

Unequal length double a-arms- found in many higher end sports car, and the older EG and EK civics. imagine a mac strut with 2 arms. why bother you say? adjustability! because of this, the actually geometry of the movement can be tweaked very minutely, for different effects. ever wonder why civics that are slammed have ridiculous amounts of camber? double a-arms are why. double a-arms can gain much more camber through its suspension travel, desireable for cornering, but not so hot for improper lowering clowns.

Solid beam axle - not found in many imports because they mostly s***, found in the ass end of camaros and mustangs, and many SUVs and big trucks. this is a non -independent design, meaning if one wheel moves, the wheel on the opposite side reacts to that. sucks for passenger cars that like to handle, especially on rough pavement. good for pure drag cars and trucks.

Suspension FAQ - All you need to know and more!

What does it do?

Apart from your car's tires and seats, the suspension is the prime mechanism that separates your bum from the road. It also prevents your car from shaking itself to pieces. No matter how smooth you think the road is, it's a bad, bad place to propel over a ton of metal at high speed. So we rely upon suspension. People who travel on underground trains wish that those vehicles relied on suspension too, but they don't and that's why the ride is so harsh. Actually it's harsh because underground trains have no lateral suspension to speak of. So as the rails deviate side-to-side slightly, so does the entire train, and it's passengers. In a car, the rubber in your tire helps with this little problem.
In it's most basic form, suspension consists of two basic components:

Springs

These come in three types. They are coil springs, torsion bars and leaf springs. Coil springs are what most people are familiar with, and are actually coiled torsion bars. Leaf springs are what you would find on most American cars up to about 1985 and almost all heavy duty vehicles. They look like layers of metal connected to the axle. The layers are called leaves, hence leaf-spring. The torsion bar on its own is a bizarre little contraption which gives coiled-spring-like performance based on the twisting properties of a steel bar. It's used in the suspension of VW Beetles and Karmann Ghias, air-cooled Porshes (356 and 911 until 1989 when they went to springs), and the rear suspension of Peugeot 205s amongst other cars. Instead of having a coiled spring, the axle is attached to one end of a steel shaft. The other end is slotted into a tube and held there by splines. As the suspension moves, it twists the shaft along it's length, which in turn resist. Now image that same shaft but instead of being straight, it's coiled up. As you press on the top of the coil, you're actually inducing a twisting in the shaft, all the way down the coil. I know it's hard to visualize, but believe me, that's what is happening. There's a whole section further down the page specifically on torsion bars and progressive springs.

Shock absorbers

Strangely enough, absorb shocks. Actually they dampen the vertical motion induced by driving your car along a rough surface. If your car only had springs, it would boat and wallow along the road until you got physically sick and had to get out. Or at least until it fell apart.
Shock absorbers perform two functions. Firstly, they absorb any larger-than-average bumps in the road so that the shock isn't transmitted to the car chassis. Secondly, they keep the suspension at as full a travel as possible for the given road conditions. Shock absorbers keep your wheels planted on the road. Without them, your car would be a travelling deathtrap.
You want more technical terms? Technically they are called dampers. Even more technically, they are velocity-sensitive hydraulic damping devices - in other words, the faster they move, the more resistance there is to that movement. They work in conjunction with the springs. The spring allows movement of the wheel to allow the energy in the road shock to be transformed into kinetic energy of the unsprung mass, whereupon it is dissipated by the damper. The damper does this by forcing gas or oil through a constriction valve (a small hole). Adjustable shock absorbers allow you to change the size of this constriction, and thus control the rate of damping. The smaller the constriction, the stiffer the suspension.




A modern coil-over-oil unit

The image above shows a typical modern coil-over-oil unit. This is an all-in-one system that carries both the spring and the shock absorber. The type illustrated here is more likely to be an aftermarket item - it's unlikely you'd get this level of adjustment on your regular passenger car. The adjustable spring plate can be used to make the springs stiffer and looser, whilst the adjustable damping valve can be used to adjust the rebound damping of the shock absorber. More sophisticated units have adjustable compression damping as well as a remote reservoir. Whilst you don't typically get this level of engineering on car suspension, most motorbikes do have preload, rebound and spring tension adjustment. See the section later on in this page about the ins and outs of complex suspension units.

Super HICAS Suspension

Super HICAS

Super HICAS (High Capacity Actively Controlled Suspension) is Nissan’s four-wheel steering system used on the 240SX. A similar system is used on the Nissan Skyline. Early HICAS designs used hydraulics for rear steering, but Super HICAS uses electronic actuators controlled by the ECM.

Four-wheel steering on the 240SX is designed to improve low-speed maneuverability and high-speed stability, especially during lane changes. Super HICAS operates in two modes: in-phase steering and opposite-phase steering. Opposite-phase steering, utilized at low speeds, turns the rear wheels in the opposite direction of the front wheels to reduce turning radius. In-phase steering, utilized at high speeds, turns the rear wheels in the same direction as the front wheels to reduce sideways motion of the car, thereby increasing stability. The steering angle of the rear wheels is limited to about one degree.

Super HICAS may facilitate better steering response and quicker corner entry in racing conditions by delaying in-phase steering or using some opposite phase steering at corner entry. However, racing with Super HICAS requires the development of a different driving style as compared to that required for an ordinary front-steering car. Many drivers report that the 240SX feels twitchy on corner entry with the use of Super HICAS. Also, the rear steering becomes unpredictable when the car is on the edge of losing traction. Therefore, most drivers prefer to deactivate the system with an aftermarket HICAS eliminator kit (see Performance section).

HICAS IN Skylines

HICAS is the acronym for Nissans rear wheel steering system named High Capacity Actively Controlled Steering. HICAS works using different sensors which calculate speed, steering angle and corner position the rear wheels are steered by a maximum of 1 degree based on these measurements. HICAS helps eliminate body and give the car a more nimble fell, it does it job well and is helpful for the average driver who doesn’t push the car to its limits. 

On a racetrack however HICAS becomes to intrusive and unpredictable, particularly on long high-speed corners, counter-steering is often needed to correct the Skyline though the corner, this is not good for lap times. Race team’s usually use a lock bar to disable the HICAS system which improves the Skylines balance, resulting in more predicable handling and faster lap times.

Earlier skylines (the R32) used a hydraulic system which had speed sensors and used the power steering pump to steer the rear wheels. The newer version named Super HICAS was used from the R33 onward; electric actuators were used a long with a onboard computer, this version saved weight, and is said to be a much improved system.

Excellent info but please mention the source.

as mentioned on other thread... most of the articles posted here have been taken from some source ... DUE CREDIT TO BE GIVEN TO THE ORIGINAL AUTHOR