Suspension modifications aren’t done just to make your car look better. The factory suspension of our cars are designed to achieve smooth ride comfort while maintaining good handling. For the performance driver or enthusiast, good handling is more important than comfort. Take note that you cannot have excellent characteristics for both handling and comfort as there will always be a trade-off between the two.
Basic suspension modifications consist of springs, sport-tuned/performance shock absorbers, strut bars. Being basic, these are relatively easy to install and should not be hard to find as well.
Coil Springs
Springs were primarily used in the olden days of the automobile as the primary suspension. There are two different kinds of automotive springs, the coil and the leaf. Coil springs are manufactured of a special round steel rolled in a specifically engineered helix shape with the use of computer aided machines. Coils are usually used in cars, modern car suspensions in particular utilize coil springs and is considered to be a major improvement from leaf springs.
Coil springs support the weight of the vehicle and allow the suspension to articulate in order to provide a smooth ride over bumps and dips in the road. Most people will attribute worn coil springs will cause the vehicle to bounce excessively, which is a common misconception. The job of providing resistance to this bouncing is for the dampers or shock absorbers or struts, and not the coil springs. In any case, over time, as with any part of your car coil springs can break or loose their strength and need to be replaced.
One of the most basic performance upgrades for suspension is to change to lowering springs which will improve handling ability and aesthetic characteristics as well. Lowering springs are specifically engineered to give a lower ride height but at the same time maintain the capabilities of the suspension coiled to a specifications which have been researched by engineers. There are things to consider before changing to lowering springs of course. Firstly, the stiffer lowering springs may not ride as comfortably as the factory springs. Secondly the lower vehicle is more likely to hit the ground over humps and bumps which could result in expensive damages to the undercarriage and exhaust system. Lastly, the altered suspension geometry would most likely change suspension characteristics like camber in particular.
NEVER CUT or HEAT YOUR ORIGINAL SPRINGS just to achieve a lowered stance. Although this will lower your car, it will also destroy the coil spring during the cutting and will not provide the necessary resistance designed for your car. This will also give you a discomfortable and wobbly ride and could also cause unwanted damage to the suspension system which could amount to a lot of money.
Types of Springs
Sport Springs
Sport springs are designed to give the least compromise for ride comfort while giving a slightly lowered ride height. These springs offer improved front-to-rear balance and street handling perofmrance. They were designed to take the wallow out of the stock suspension to give a more stable feel and imporved ride characteristics. These springs are designed to be installed with the stock shocks.
Race Springs
Race springs are designed to be more aggressive thus higher spring rates and a lower ride height is also expected for a lower center of gravity. Thus, the design follows with the type that these springs are not recommended for use on the street as they will not be comfortable at all. A low ride height would introduce scraping underneath the car which can cause damage to parts, and add to that the discomfort in the ride for both the driver and passengers. Race springs will usually require the installation of stiffer shocks to complement the stiffer spring rates to maximize performance.
Shock Absorbers/Dampers
Shock absorbers were introduced to dampen the up and down oscillation of springs. The first shock absorber simply two arms connected by a bolt with a friction disk between them. Resistance was adjusted by tightening or loosening the bolt. Durability was a big issue and through time, shock absorbers have evolved into more sophisticated designs.
Contrary to a common misconception, shock absorbers do not support the weight of the vehicle but rather control the movement of the springs and the suspension. Shock absorbers control the movement by converting kinetic energy from the movement into thermal energy which is dissipated through the hydraulic fluid. The shock absorber is therefore basically an oil pump.
The shock absorber is therefore basically an oil pump which works on the principle of fluid displacement. A piston is attached to the end of the piston rod and works against hydraulic fluid in the pressure tube. As the suspension travels up and down, the hydraulic fluid is forced through tiny holes, called orifices, in the piston. However, these orifices let only a small amount of fluid through the piston. This slows down the piston, which in turn slows down spring and suspension movement. As a result of this, shock absorbers reduce bounce, roll or sway and brake dive and acceleration squat.
Shock absorbers work on the principle of fluid displacement on both the compression and extension cycle. A typical car or light truck will have more resistance during its extension cycle then its compression cycle. The compression cycle controls the motion of a vehicle’s unsprung weight, while extension controls the heavier sprung weight.
Gas Charged Shocks
The development of gas charged shock absorbers was a major advance in ride control technology, which solved many ride control problems which occurred due to an increasing number of vehicles using uni-body construction, shorter wheelbases and increased use of higher tire pressures.
The design of twin tube gas charged shock absorbers solves many of today’s ride control problems by adding a low pressure charge of nitrogen gas in the reserve tube. The pressure of the nitrogen in the reserve tube varies from 100 to 150 psi, depending on the amount of fluid in the reserve tube. The gas serves several important functions to improve the ride control characteristics of a shock.
The prime function of gas charging is to minimize aeration of the hydraulic fluid. The pressure of the nitrogen gas compresses air bubbles in the hydraulic fluid. This prevents the oil and air from mixing and creating foam. Foam affects performance because it can be compressed – fluid can not. With aeration reduced, the shock is able to react faster and more predictably, allowing for quicker response time and helping keep the tire firmly planted on the road surface.
Sport-tuned/Performance Shocks
These are essentially twin-tube gas-charged shock absorbers which have modified valves to accommodate more aggressive driving and provide better handling characteristics to the car by improving road holding, reducing bounce, roll, sway and dive. Sport shocks are a good companion to sport springs and gives a minor boost to the spring rates to optimize its performance.
Sport tuned shocks are available in either standalone or in a package with specifically designed springs to work together. The sport suspension kit is normally recommended to avoid the problems with equipment matching as they have been engineered and tested to work together.
Strut Bars
The strut bar is one of the most common modification which is done to a car which improves handling dramatically. Some factory performance tuned cars come with strut bars installed. And yet, not everybody knows its purpose. The purpose of the strut bar (strut tower bar) is to tie the two opposing strut together as a single unit.
This upgrade’s main purpose is to reduce chassis flex on hard cornering. Normally the strut towers flex on cornering, resulting in body flex and loss of traction, because as we all know there is no traction in the air. The strut bar is designed to keep the struts from flexing by distributing the amount of force applied on one strut tower when taking a corner to both towers. This helps keep the tires in the desired position on the road, thus improving traction, exit speed and laptimes on the track.
Strut Bars
The strut bar is one of the most common modifications done to a car which improves handling dramatically. Some factory performance tuned cars come with strut bars installed. And yet, not everybody knows its purpose. The purpose of the strut bar (strut tower bar) is to tie the two opposing strut together as a single unit.
This upgrade’s main purpose is to reduce chassis flex on hard cornering. Normally the strut towers flex on cornering, resulting in body flex and loss of traction, because as we all know there is no traction in the air. The strut bar is designed to keep the struts from flexing by distributing the amount of force applied on one strut tower when taking a corner to both towers. This helps keep the tires in the desired position on the road, thus improving traction, exit speed and laptimes on the track.
Rear strut bars are designed similarly to work like front strut bars by tying the two rear struts together. This upgrade improves overall chassis stiffness, minimizes understeer due to less chassis flex, and improves stability when braking into corners as it helps maintain balance for the vehicle.
Strut bars are indeed a very good addition to spring and shock upgrades as these combined with wider wheels and tires add extra stress to the chassis. Strut bars not only contribute to the sub-frame of the vehicle but also add to the overall chassis stiffness. And with a better performing chassis, steering response improvement can be achieved as well.
On most if not all applications, installation can be done in minutes and some particular aftermarket models look shiny and cool. At least now you know there’s more to its being shiny and cool. And looks don’t exactly have anything to do with performance. When choosing a strut bar, choose the most rigid design as possible to make the most out of the money you are spending.
Sway Bars/Anti-roll Bars
Sway bars tie the lower suspension components together across the front or back. These are also otherwise known as stabilizer bars which are connected to stabilizer links. This affects the handling of the car on the lower end of the suspension. They can either affect a car’s oversteer and understeer.
The task of the sway bar is distribute the energy made by the turn from one side to the other to balance out the car, keeping it flat instead of letting it lean to one side. But it does not necessarily mean that the car will not lean at all, it will only minimize the lean. Most modern cars come with sway bars standard for the front and some even on the rear. But these standard sway bars can be upgraded to thicker diameter ones which further minimize the lean.
Now that you know the basics of suspension tuning, you now know that there is more to making your car look better with changing to lowering springs and adding strut bars. You must have learned by now that cutting springs is definitely a no-no in any application whatsoever. It is a common unsafe practice done by people who try to be engineers of their own practice. Having an uneven ride height (in most common cases excessively higher rear suspension) is also not recommended as it adversely affects the cars balance and handling. But in some applications, drag racing specifically, these give minor performance and traction improvements. But take note that it is unsafe to drive with this setup on the street.
