View Full Version : Suspension related FAQ

11-21-2005, 03:35 PM
Q: I often hear the terms strut and shock used interchangeably. Are they different?
A: Shocks and struts are similar in that they both damp (slow down) the vehicles motion. The key difference of a strut vs. a shock is that a shock only controls the cars motion while a strut is a locating member of the suspension. What this means is that if you remove a shock, the spindle or axle will still be completely attached to the vehicle. If you remove a strut, the spindle or axle will be able to move outside of its normal motion. Shocks and struts may or may not have a spring mounted to them either. It is often assumed that any damper with a spring is a strut, but this is not the case.

Q. What is rebound damping?
A. A damper, also known as a shock or strut, has two ranges of motion. As the shaft of the damper extends out of the damper body, the damper is in rebound. In application, as your vehicle exits a bump, the dampers will rebound. The core function of rebound in a damper is to provide the roll control of the vehicle. Another function of damper rebound is to control the spring rate on the car. A car with too little rebound will be unable to control high spring rates. Much like putting an aggressive spring rate on a soft damper (like an OEM damper) will result in poor overall ride quality.

Q. What is compression damping?
A. A damper, also known as a shock or strut, has two ranges of motion. As the shaft of the damper compresses into the damper body, the damper is in compression. In application, as your vehicle enters a bump, the damper will compress. Compression damping is the primary factor in ride quality, road compliance and steering response. Compression force can also act as additional spring rate in a car. It is possible to run a strong compression damper, with a very soft spring. In comparison, it is not good to run a very strong spring with a very soft damper.

Q. Why are STaSIS suspension products more expensive than others?
A. Most suspension kits are comprised of off-the-shelf dampers mated to a set of springs. These off-the-shelf dampers are typically valved to meet a range of vehicles and are produced in high volumes. In comparison, STaSIS valved dampers are engineered specifically to each chassis and per the clients’ requests. This increases the complexity of the damper valving and drastically reduces the production volume. In addition to the damper valving, STaSIS Track Sport and Motor Sport suspension kits utilize Hyperco flat wound race springs. These race springs require CNC parts to be included in the kits and this adds more to the overall cost. However, by using a standard race spring, clients can choose for a wide variety of available rates and customize the suspension in their car to meet their specific or changing needs. Given that flexibility, the STaSIS suspension can be tailored to suit your needs as well as be modified over time as conditions and driving style grow.

Q. Won’t high spring rates make the ride harsh?
A. No. The primary function of the spring is to control the roll of the vehicle. Body roll, brake dive and acceleration squat are all functions of spring rate. By increasing the rate of the spring, you decrease the movement of the body. Ride compliance and harshness are more a function of high speed damper compression resistance than spring rate.

Q. Can I use STaSIS’ Hyperco linear rate springs with my current suspension?
A. Not really. STaSIS uses Hyperco flat wound race springs in our Track Sport and Motor Sport suspension kits. Without modifying the upper and lower spring perches, these flat springs will not fit correctly. In addition to that is the fact that most dampers will not be properly valved to control higher rate springs than what are recommended or included with the kit. In order to utilize OEM upper and lower spring perches, you will need a taper wound spring that is designed around the OEM specifications of the vehicle (for taper size and overall length).

Q. What is digressive and double-digressive damping?
A. Digressive damping describes the style of damper valving. Double-digressive simply means that the damper valving is digressive on both the compression and the rebound side of the damper. Digressive (as the name implies) means that the compression or rebound force will change or digress from a given path at some point. In comparison, a linear rate damper follows the same increasing path. The amount of digression and the point at which the compression or rebound digresses are part of the valving of the damper.

Q. Do I need to align my car with my suspension install?
A. Not right away. STaSIS recommends waiting up to 2 weeks after your suspension installation to have your car aligned. As long as ride heights at each corner are set correctly and all suspension fasteners have been torqued at ride height per the service manual requirements, no adverse affects on alignment will occur with the suspension installation. That being said, any minor alignment issues with a stock suspension (slightly off center steering wheel, slight pull to one side) can be exaggerated when the car is lowered. The reason for waiting 2 weeks is two fold. First off, it is important to verify that the car is not doing anything out of the ordinary that it was not doing prior to the suspension install. The second reason is to allow the new dampers and OEM spring perches to settle a bit. After this, an alignment is advised. For recommended alignment settings, see the frequently asked question: What are your recommended alignment settings?

Q. Do I need to corner balance my car with my suspension install?
A. Not immediately. Corner balancing is a great advantage to a car with adjustable ride height, however there are some aspects that make it insignificant in a street car. The amount of soft rubber bushings in the OEM suspension design makes for a decent amount of flex to the suspension. So even at a perfect 50.00% cross weight, the flex of these bushings will not provide that same 50.00% cross weight when loaded. However, the adjustable height suspension kits offer the ability to corner balance the car if that feature is important.

Q. What are your recommended alignment specifications?
A. Alignment settings are dependent on many factors including acceptable tire wear, the amount of straight line highway driving versus twisting street driving and the overall goal of the car. So first it is important to decide what types of driving the car will mostly do and what sacrifices you are willing to make. It’s also worthwhile to understand the tradeoffs of each alignment characteristic. Toe: zero toe (or even toe out) is great for turns, but you sacrifice straight line stability. Camber: negative front camber is great for turns, but you sacrifice uneven tire wear and require more frequent mounting and balancing (and rotation) to keep tire wear manageable. Also, with the OEM solid upper control arms, your camber will be a factor of ride height. With adjustable upper control arms, ignore the ride height recommendations and set camber accordingly. Feel free to contact a Matrix Integrated team member for more specifics on your application.