The big bar, soft spring setup can be very complex, but understanding it can greatly impro
Few advancements in technology have made as big an impact in the asphalt racing world as the big bar, soft spring setup (BBSS).
This setup utilizes soft springs in the front of the car complimented by a larger front sway bar. This doesn't sound especially complex, but problems arise when teams begin trying the BBSS and change only the front springs and the sway bar when, in truth, the entire setup has to be rethought.
The BBSS allows the front end of the car to be lower, creating a lower center of gravity. This usually is accompanied by stiffer rear springs to keep the front end of the car pinned to the ground in the corners, and this will also keep the rear spoiler in the air throughout the corner. The BBSS is mostly used in Late Model racing. However, the same principles can be applied to Street Stock or Pure Stock racing. The BBSS can improve lap times by allowing the car to be driven in deeper, being able to keep it on the bottom of the track, and allowing the driver to get on the throttle sooner.
The goal of the BBSS is to keep the nose as low as it can be in the corners. The soft spri
So why should you be running the BBSS in a Late Model? There is no real reason to be using this setup-if you are winning every weekend with a conventional setup. Otherwise, this is something else to put underneath the car to try to pick up lap times and make the car handle better. The Late Model bodies of today are so aerodynamic that the softer front springs will increase the amount of downforce being applied to the nose of the car by keeping it lower. When you mash the brakes entering the corner, the front end will drop and seal the nose to the pavement, thus limiting the airflow underneath the car, allowing the air to push the tires into the track and give you more front grip.
Now, I can imagine a lot of you saying, "I race on a track where we don't even break 90 mph. Don't talk to me about aerodynamics. This isn't NASCAR!" The thing to remember, though, is aerodynamics come into play with anything above 35 mph. I ran a race in Go-Karts a few years ago where there were four of us drafting at around 55-60 mph. We picked up 0.3 second by drafting and staying in line. If you still aren't convinced, the next time you are driving down the highway at 65-70 mph, stick your arm out the window and put it straight down perpendicular to the pavement. Now try to extend your arm and make it horizontal. Of course you will be able to do so, but notice the forces on your arm while you are moving it to the horizontal position. These are the same forces that are affecting your racecar.
This is what a car should look like as it travels through the corner. Notice how the car i
Once the springs are compressed and you steer the car, the forces being applied will try to push the weight of the car to the right side. This is called body roll. This is why a big front sway bar is needed-to counteract the body roll in the corners. The larger front sway bar will keep the car from transferring as much weight and help keep the left front of the car pinned down through the corner.
When you apply throttle, the weight will start heading back to the right rear of the car and try to pick up the left front tire. You will notice this because the left front of the body will have a gap between it and the racetrack. A few inches is common when the throttle is applied but, if you notice that there is a big split between the right front of the nose and the left, then you should add more right-rear spring to hold the nose closer to the pavement. Most of the time in these situations, the car is going to be tight anyway, so adding that right-rear spring will help the car turn from the center of the turn to the exit.
Front End Geometry At No Travel, Sitting In The Shop This is what front end geometry look
A small controversy involves the left-rear spring. Some advocate a softer spring on the left rear than on the right rear, so the weight will transfer to the left-rear tire and drive off of that tire when the throttle is applied. Others advocate running about a 50 to 100 pound split between the two spring sizes because, just as the right-rear tire picks up the left front, the same will happen with the right front. This line of thought maintains if you run a stiff right-rear spring, the weight won't be able to transfer there and instead will transfer to the left-rear spring, which, in turn, will pick up the right front of the car, causing a push when you exit the corner.
I tend to side with the second opinion. Anytime I have run a large split between the two springs, I feel that I'm about to knock the wall down when exiting the corner. To determine if you have enough left-rear spring in the car, run a few laps to see if the car is really tight off the corner. If it is, change to a stiffer right-rear spring. And try a big jump of between 100 and 150 pounds. If the car is still trying to push off the corner, then you know you are lifting the right front up when you are getting back on the gas. Now you need to go stiffer in the left-rear spring.