Suspension Guide - General Suspension Tuning Guide
Today we’re going to look at some items you might not know about when it comes to suspension and go over some variables that make big differences on the track and the street. Let's roll.
Tires
Though not commonly talked about when people discuss suspension this is where everything starts. Tremendously grippy tires change the entire character of a suspension setup and it’s the first thing you need to pick. An ultra sticky tire is going to permit more lateral force and to adjust for this you’ll need to go a little more heavy duty setup. Conversely, if you are on a performance 200 tread wear tire (Direzza Star Spec) the lateral grip will be substantially less than a sticky slick (Hoosier A7). Suspension tuning works from the ground up. Power matters too. A car with more horsepower and torque may have a harder time maintaining traction than a vehicle with substantially less power.
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Springs
The next major factor in a car’s handling is the springs. Having a super soft racing tire will require stiffer springs to keep body roll in check. The vehicle's weight and power come into play here as a car with higher horsepower will cause the car to squat down more under acceleration. Springs are measured in a number of lbs it takes to compress the spring 1 inch (lb/inch) or how many kilograms it takes to compress per millimeter (kg/mm). A spring has energy so once it’s compressed it will naturally want to decompress. We have to keep this in check! Which means...
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Shocks
The way we keep the springs in check is with shock absorbers. Think of the shock and spring as partners. The shocks job is to keep the spring out of trouble and control how fast or slow it moves. A good performance shock is vital in cutting lap times down and improving ride quality. It is also one of the biggest overlooked modifications you can make to a vehicle. Not many guys brag about this mod, but they are worth seconds on the track! Great shocks allow higher spring rates without discomfort and can be adjusted for various conditions. The spring rate you run determines the shock you need. Run too much spring without the right shock and the shock won't keep up.
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Sway bars and end links
Sway bars resist roll and are a pretty common performance modification. End links are not really discussed as much. The sway bar has to mount to the body and the way they do this is through end links. Unfortunately, a sway bar can have something called preload. Preload is a force generated on the bar when the car is not in motion. As you drive you may notice the car takes a left-hand turn better than a right-handed or vice versa. Adjustable end links allow the bar to sit unstressed right to left making it equally effective at turning both ways.
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Caster, Camber and Toe
These 3 come together to create your alignment. Ideally, you want the tire flat in a straight line for the best acceleration and flat in a corner for the best traction. Unfortunately, you have to strike a balance between the two. Camber and toe work in tandem with each other to create a flat contact patch and affect everything from steering to braking feel. Tire wear tells a lot about alignment and should play a major role in how you fine tune your setup. Caster relates to steering feel and stability. It is referred to as positive and negative with positive yielding greater stability and confidence at higher speed, but an increase in steering effort. The picture above is not the correct way to align a car!
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Final words
Fundamentals are important to have a grasp of as you move onto higher level tuning. Things like asymmetrical setups, corner weighting and various configurations of internal shim stacks within a shock are the next things to start diving into. We’ll explore these three topics in three individual articles to really capitalize on their importance and help in simplifying why they are necessary.
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