The BBSS setups have dominated...
The BBSS setups have dominated some series, such as the USAR Pro Cup. Even at the year-end Rockingham race, most teams ran on bump rubbers or coil bind despite the 22-plus degree banking in the turns.
It's the end of another season of racing and most teams are reassessing their efforts and starting to plan for next year. The Big Bar and Soft Spring setups that have been the rage in asphalt racing circles continue to be of interest. Many teams that have had success running more conventional setups are thinking of changing to the setups that use a large sway bar combined with soft front springs and a stiffer right rear spring. When making this change, you can't just bolt those parts onto your car and go racing and expect to be successful.
We have talked to many teams and component manufacturers about the transition and we have run those setups in back-to-back tests against conventional setups. In short, we have a lot of information to share. A lot of teams continue to struggle trying to make the BBSS setups work. Most admit that maintaining a balance with these setups is much more difficult than when they ran conventional setups.
The goal of the BBSS setups...
The goal of the BBSS setups is to allow a much more efficient front aero package by causing the front end to be lower to the racetrack. This reduces the flow of air under the car and allows the low pressure to build that causes downforce.
The very first thing to know is that the BBSS setups are not going to be right for all racetracks. There are some tracks where the gains are significant and others where there is either no gain at all or where the more conventional setups are just plain faster. We'll explain why.
Let's take a look at what our goals might be in going the BBSS route. Most ill-handling cars are traditionally tight and will not turn well. The BBSS setups do help the car to turn better by forcing additional load onto the Left Front (LF) tire.
Handling balance can be accomplished with adjustments to the weight distribution meaning a change in crossweight percent. So, making the car neutral once we have gone to the BBSS setup is usually not a problem.
Aero efficiency is improved, sometimes greatly improved, on longer tracks due to the front valance being lower and the rear spoiler being higher. The soft front springs compress more and the stiffer RR spring forces the LF corner down to where the front of the car is low and parallel to the track in the turns.
Here we see a typical conversion...
Here we see a typical conversion from a one-piece sway bar to a NASCAR-style three-piece sway bar. Some teams like the way the three-piece bars react more efficiently to the forces generated by the BBSS setups.
There are some interesting results that come from the transition. First of all, if the car is setup "right", meaning all of the way to BBSS as it is applied in most cases, and we'll explain what that means later, the dynamic balance could be way off. The front wants to roll to say 1 to 1.5 degrees and the rear wants to achieve a negative roll angle of from 0.5 to 1.0 degree.
This difference in desires means that a lot of extra load is being put on the RR tire. In older traditional setups that were unbalanced, the rear out-rolled the front and a lot of extra load ended up on the RF tire. That tire soon began to overheat and loose grip. The car either pushed badly or the driver could overcome the tight condition with extra steering input until the car went to a tight-loose condition.
The final result was either a worn out RF tire or a burned out RR tire. One of the two was sure to go. So, the big question is, why doesn't the RR tire give up on the BBSS setups similar to the RF tire that was overloaded with an unbalanced conventional setup?
We pondered the very same question and finally came to a conclusion. When the car is unbalanced with the rear out-rolling the front, the RF tire has to not only carry a lot of extra load to keep the car on the track through the turns, but it also works to make the car change direction and turn the car. It's the extra duty of turning the car that overloads the RF tire and causes it to give up so quickly on a conventional setup.