Why a balanced setup is better than a "understeery" setup.
 

This is a snapshot of data being taken from two different cars at the "Sweeper" at Buttonwillow Raceway Park, which is a flat, 180 degree turn. The lines are as follows:

- GPS Speed (Speed as determined by GPS, not by the car's ECU)
- Steering angle in degrees
- Gas pedal input (in percent from none to WOT)
- Lateral acceleration as determined by GPS (Lateral G's)
- Rate of yaw, as determined by GPS (yaw rate in degrees per second)
- Lap time differential between the green and blue traces

https://fbcdn-sphotos-e-a.akamaihd.n...31176518_o.jpg

The first thing to note, is that the green car is slower through the entire corner (graph 1); the corner is identified by the red line at the top of the graph labeled "16".

The second thing to note, is that the green car reaches peak cornering grip (graphs 4 and 5) at about 80 degrees of steering input (graph 3), whereas the blue car only requires about 60 degrees of steering input. Even with less steering input, the blue car actually maintains higher cornering grip (compare the green and blue lines on graphs 4 and 5)!! The time gained by the blue car is shown by the differential dropping in graph 6. Even though the Green car is on the throttle more through the second half of the corner, it actually makes the understeer worse, and the blue car is able to go faster!


The Green car is representative of coilovers that utilize the same spring rates front and rear, or have a small stagger with the rear being larger.

The Blue car is representative of cars that utilize coilovers that have a 20-25% higher spring rate in the rear.

This is awesome!

Nothing like braking with front tires while getting on the gas ;)

Mike why are you so cool?! Lol

Great info man!

I'm becoming a firm believer of this.

Now, what are the best options that take advantage of this?

There are a TON of ways to achieve proper balance. However, fine tuning it will require you to have a highly experienced local driver that can guide you, or you need to be willing to spend a lot of time learning to do it yourself.

For example, you can take ANY suspension, and literally "hack" the balance together by changing the spring rates. But, then the dampers wont match the springs. Or, you can change the sways to change the effective spring at the wheel, but again, dampers.

The real problem, is that unless a 1 way system is very carefully designed to be balanced (and there's none that I'm aware of on the market for this car, or most cars for that matter), you need at least a two way damper, so that you can change springs to taste, and still be able to critically damp the springs.

Also, most cars understeer from the factory. This is done intentionally by design, because the natural tendencies of the average driver suits understeer better than balance or oversteer.

This is also why rates of 10k/12k were selected as our default for the CSG-Spec SRCs. Not only does it balance the car, it lets you use your tires and fuel more efficiently. However, we do also acknowledge that "balance" means that without a lot of experience, it's very easy to unintentionally make the car rotate (spin), so rates of 9k/10k are recommended with the CSG-SRCs, for the less hardcore drivers. Furthermore, some setups actually require MORE static rotation. @ImperiousRex's BRZ with JRZs for example, was set up by CSG to utilize 9k/11k spring rates, which would normally result in a car that wants to oversteer everywhere. However, the car's geometry, sway bar rates, and aero were all simultaneously tuned to work in conjunction, resulting in a beautifully balanced car that is still the fastest privately owned track FRS/BRZ in North America.

This type of balance can be achieved with most mid-grade and higher 2 way dampers.

Are these cars using the exact same tires?

I don't disagree with anything you have said. Are they the same driver? Same tires? Also assuming that these aren't stock cars?

There are a lot of factors as you know that could make these results.

Nice data, thank you. What is the rest of the setup like for the cars? Tires, bars, dampers, alignment/camber, absolute spring rates/stiffness, aero, ride height?

And yet @ImperiousRex chose to take a S2K to COTA.

Tsk tsk.

-alex

Great questions.

- Tires don't change the static balance of the cars. However, having more grip than what the car itself can readily overcome can hide handling imbalances. In this case, both cars used comparable (but not identical) tires.

- Both cars are on stock sway bars.

- The balance is determined by spring rate at the wheels, not the dampers. You can FORCE a change in balance by *reducing* grip at an axle, by using incorrect dampers. While the damper models are different, both cars were critically damped.

- Both cars had alignments to maximize on-track performance. Alignments were slightly different to accommodate spring rates, but are within a few tenths. Both cars have zero toe front and rear.

- I unfortunately cannot disclose the absolute spring rates without potentially revealing the coilover models. This post is purely to demonstrate the difference between a balanced spring rate f/r versus a common "front spring heavy" car.

- Both cars have zero aero.

- Ride heights were set to manufacturer recommended heights.

Comparable, but not identical tires.

I am the driver in both cars.

Both cars are mildly modified, but none of those modifications, IMO, have any significant impact on the car's behavior in static corners. For example, one car could be turbo, but that extra power wouldn't change how the car takes a 180 degree, flat surface turn, unless you were drifting. Both cars are NA, and lack sufficient power to hold a drift at that speed.

:bellyroll: :bellyroll:

I was supposed to take the BRZ as a support car... but budget issues...

You're the driver?!?!?? Lord help us. :bellyroll:

Right on! Sounds like a great comparison. :)