Suspension for Beginners

This is a crash course for all suspension related components. The technical level is not extreme, but hopefully this will end all "what shock" and "springs vs. coilovers" threads...

Tires

This is the only part of your car that makes contact with the ground. This makes it the MOST important part of your suspension. The area that
contacts the ground is rightfully called the contact patch. The shape of the contact patch affects how the car reacts to driver inputs. A wider contact patch will improve straight line performance, such as braking and accelerating, while a longer contact patch will improve cornering forces.

Different compounds and tread patterns react differently in real-world situations. There are very definite limitations to traction. The tire works by locking in with the imperfections in the road. A softer compound tire will fill those crevices better, but will wear more quickly.

Tires also need to operate in a certain temperature range. Street tires operate in a considerably wider range of temperature than race tires. If you are running slicks at the strip, or heavy-duty R compound tires, check the manufacturer’s specs on temperature.

Camber kits

There are many factors that go into HOW the tire makes contact with the ground. Among these is camber. If you are looking at a car and the tires look like this: / \ Then you have a camber problem. Camber can improve your handling, but if it goes too far, it will eat up your tires and actually reduce traction. I believe acceptable camber for Integras is between 0 and -1.5 degrees.

Toe

Toe is another important factor in your suspension. Toe-in moves the front of the tires towards the center of the car and toe-out moves the front of the tires away from the car. Toe has a drastic effect on slip angles, which are discussed in a different article.

In an improperly designed suspension, toe may change when the car hits a bump. This is called bumpsteer, and is very scary for a driver. The car will try to dart to one side when the toe changes.

Wheels

Yes, they do more than just look good. Size and weight drastically change the performance of the car. A heavier wheel equals more unsprung weight (covered in a minute). A larger wheel means you will be running a tire with a shorter sidewall. As a rule of thumb, the shorter the sidewall, the thicker manufacturers make it. Due to a shorter height, it is also more resistant to rollover. This improves handling and ensures you manage a larger contact patch.

Springs

Springs are very important in determining the responsiveness of your car. All weight above the springs is called "sprung weight." While this has an effect on drag, the main concern is "unsprung weight." Unsprung weight is basically what the engine is trying to move, and what the shocks are trying to dampen. A generally accepted ratio is adding 1 lb. of unsprung weight is like adding 10 lbs. of sprung weight. Consider that before you buy your bling bling dub-deuces.

Besides supporting the weight of the cabin, springs also affect how the weight in the car is distributed. For those of you with upgraded springs, you might have noticed the car doesn’t rock back as far when launching. Springs push against whatever force is applied to it, so when your car leans in a direction, the springs counteract that. The stiffer the spring, the more it prevents weight transfer. This is why racecars use stiff spring rates. On uneven terrain, though, the spring might not react quickly enough to keep the wheel in contact with the ground.

There are two types of spring designs: progressive and linear. Progressive springs are designed for comfort without giving up too much in the way of handling. They are coiled in a way that provides a low spring rate when uncompressed, and stiffens the farther the spring is compressed. This means you don’t have a stiff ride, but can still have some fun. They are inferior springs for real racing. Linear springs have a set spring rate that does not change. This can be soft for a luxurious ride, or ultra stiff for precise handling, or anywhere in-between. Linear springs provide a much more predictable feel.

Shocks

Ever see a car with cut springs that just bounces as it is going down the road? These people have blown out their shocks. Shocks act as a damping force to keep the springs from constantly compressing and decompressing (that is why they are sometimes referred to as dampers). The more force applied to the shock, the stiffer it becomes. If you ever install shocks, try compressing the shock on the ground, slowly. It smoothly compresses without much trouble. Now suddenly throw your weight on it. Nothing will happen until you relax some of the pressure. This is how a shock stabilizes the weight of the car.

A few factors go into choosing a shock. First of all, the travel of the cylinder. Shocks like to function towards the middle of their compression distance. That is why some shocks aren't warrantied, or don't perform well past a certain drop. When the shock is forced to perform at full extension or compression, it won’t be able to dampen properly and will blow. The other factor is the valve rate. Shocks have lots of little valves in the body that use a gas or liquid to create compression. As stated earlier, the faster the compression the more pressure the gas or liquid creates. However, if the valves aren't sized correctly, they will blow. This is why you avoid lower end shocks if going with a stiffer race-type spring. True coilovers and sleeves There are two different suspension setups that are referred to as coilovers. The first is a true coilover system. These are designed for the hardcore enthusiast and racer. They comprise of an adjustable height spring with a custom valved shock. The shock will always be designed to work perfectly with the spring, so blowing them isn't a concern. They are almost fully adjustable, so they have the versatility to work with any type of racing. The downside is the high price tag. These systems start at $750 and can range up to $2000 and more.

The other choice is technically a coilover sleeve. This unit is only a spring mounted to hardware that allows a height adjustment. Most are low quality and come with cheap springs. They can be found for low prices and the adjustability is a plus for many people. Some of the better brands are Ground Control and Skunk 2. The Ground Controls can be purchased with a custom spring rate, which makes them a favorite with autocrossers.

Swaybars

These basically tie the driver and passenger side suspensions together. When cornering, the swaybar will torque and apply pressure against the outside wheel, using the inside spring as leverage. In an extreme situation, this can double the spring rate on the outside wheel. Swaybars have no effect when driving in a straight line and only act when turning.

Bushings

These are almost always overlooked and make a big difference, especially on older cars. Factory parts use rubber bushings between suspension components to absorb vibration. The downside is that these flex somewhat, and over time deteriorate completely. Polyurethane bushings tighten up the entire suspension for a much stiffer feel.

Tie bars

These "tie" the sides of the chassis together to keep it from flexing. Under some extreme circumstances, the chassis is more willing to flex than the suspension. This is almost solely found when running extremely high spring rates, or very thick sway bars. The springs and shocks are unable to do their job, so the car will be unpredictable and hard to turn.

Limited Slip Differentials

An LSD works to increase traction, which by now we all know means an increase in handling. There are different mechanical styles of LSD's and then different settings on them. Let's start with the easiest, and what most of us have

Open Differential: This is how everyone but the ITR's start. A differential allows the tires to run at different speeds. This allows the car to turn, because the inside wheel will always be traveling a shorter line. So the power goes to the outside wheel which has a harder job to perform. To make it easy, with an open diff, the wheel that is spinning more gets the power. That means that during a high power launch, only one tire will get the power and keep spinning. So, in all their wisdom, the car gods created limited slip differentials.

Clutch LSD: I believe the Kaaz is a clutch type. These transfer power through a clutch in the differential. As one wheel starts to spin, the clutch applies pressure and transfers power to the other wheel. The more pressure, the more power transferred. This is your standard racing LSD. There are three further settings of clutch-type LSD.

1-way: Power will only be transferred while accelerating
2-way: Power is transferred on acceleration and deceleration. On RWD cars, will cause more oversteer.
1.5-way: A compromise between the two.

Viscous LSD: Think of stirring a large jug. If you only stir the top half, eventually the fluid at the bottom will start to move in the same direction. This is how a viscous LSD works. Two plates are on either side with fluid in the middle. When a wheel starts to slip, the plate spins, causing the fluid to spin the other plate. The downside is this take a little time, so isn't first choice in a performance only atmosphere.

These LSD's are always 2-way.

Gear LSD: Think Quaife. For a street driven car, this is my favorite. It offers the response of clutch-types with complete ease of maintenance. The downside is the inability to hold large amounts of power.