Spring rates mean little unless we know about the suspension systems in our race cars. Tea
The primary components used to set up a stock car are the springs. When we have chosen the correct spring rates that complement the corresponding moment centers and the weight distribution, then we get what we want-a balanced and fast race car. All too often we crutch the car using inappropriate spring rates that serve to balance the handling, but not yield the desired result of consistency.
In order to win races, our car must be fast, not only right out of the box, but at the end of the race, too. In fact, many races are won by cars that may not be the fastest in the early laps of the race, but prove to be faster than the field at the end of the race. The key is to make sure we give the car what it wants so it will be fast as well as consistent.
In a short sprint race of 25 or 30 laps, a jack rabbit setup may work relatively well. A team with a well balanced setup that may start off a couple of tenths slower for the first 10-15 laps may not have enough time to take advantage of everyone else's lap times falling off. In a 50- or 100-lap race, the car that falls off less as the laps move past lap 25 or so will have a much better opportunity to win. A car that is closer to being balanced will have the best chance to win in any length race.
A far too common sight is a team swapping springs to find that perfect handling balance. I
The key to chassis performance, whether you are on dirt or asphalt, is to work toward a more balanced setup. This can be done by trial and error (by far the most commonly used method) or by computer analysis. In the past, trial and error took a lot of time, and the teams really had no idea when the proper balance was achieved. We now have discovered indicators that we can use to help determine when we have truly achieved a balanced setup.
Many odd arrangements of springs have been tried. We are now seeing some of the racers across the country trying new methods to find a balance. For every car, there may be dozens of combinations of spring rates, moment center designs (front and rear), and weight combinations that will balance the car. Here are some considerations concerning springs when trying to balance your stock car.
The first thing to know when considering which springs to use in your race car is the exact spring rate for each of your springs. You must test each spring and do it in the proper way. You need to know the rate of your springs at the ride height. You will also need to know the range of rates they will be working as that relates to the corner of the car where the spring will be working.
It is a good idea to buy or borrow a good quality spring rating device so you can accurate
Theoretically, we should rate a spring based on the corner of the car at which it will be used because of the different ranges of motion. For the left-front (LF) spring, we would measure the height of the installed spring and compress the spring in the spring rating device to that exact height before rating. Because this corner might bump and rebound up to an inch or more, check the rate up and down 2 inches from the installed height.
The right-front (RF) spring is mostly in compression, or bump, so we would compress that spring to the installed height and then further compress it 2-3 inches to find the average rate within the range. Remember there is an installed motion ratio, and the spring is moving less than the wheel, so we don't necessarily need to compress the spring as much as the wheel moves.
The right-rear (RR) spring is also mostly in compression, so, to simulate how the spring compresses on the racetrack, it would be compressed initially to ride height and then up to 4-5 inches further, depending on the shock travels that we read after a run. Remember that we are mostly interested in the spring rate at full compression because that is where the car is going through the turns and where proper handling is most important to performance.
The left-rear (LR) spring reacts similarly to the LF spring and is in some rebound on entry and some compression at mid-turn. This spring would be rated by compressing to ride height and then up to 2 inches up and down. For dirt-car applications, this spring may rebound quite a bit as the left side jacks up for some slick track setups. In this case, the spring may be near the free (unloaded) height at mid-turn and compressed down the straightaway.