Chuck S

Any idea how stiff (spring fare) this wonder sway bar is? Replaces all five (5) OEM sway bar spring rates with a single, magic bar.

-- Chuck

twohoos

Actually the 02/03 swaybar specs are the most extreme of all. Though each 02/03 bar is softer than the corresponding 00/01, the 02/03 set is biased much more towards the rear, i.e. towards oversteer. The 02/03 coil springs *slightly* compensate for this, but overall the 02/03 is quite noticeably looser than the 00/01, and of course *far* looser than any of the AP2 setups.

Mr.Matchbox

Surprisingly, in his suspension book (The Bible) the german suspension expert Wolfgang Weber - wich raced the S2000 - often mentioned the S2000.
Regarding the swaybars, he wrote that usully the front is thick and the rear is thin, but he mentiones the S2000 as example (again), this time as the exception of the rule:
"Looks like there where some minor problemes in the development (Suspension finetuning) at the factory.... because the rear one is much stiffer and thicker .. wich is extraordinary"

https://www.motorbuch-versand.de/pro...erfektion.html

twohoos

There's no doubt the rear of the car wasn't fully sorted during development. Besides the large rear bar, the tire stagger was quite extreme: far, far more than the tire specs would suggest. Accounting for tread gaps, "shoulder" shape, and wheel width, the 205 fronts were more comparable to 195s, and the 225 rears were more comparable to 245s. (And remember, the Bridgestone S02s on the S2000 were designed specifically for the car, so this "extra" stagger was intentional.) Why put so much of the tire grip at the rear, only to take it away with a huge bar?

There's a lot to unpack there, but the bottom line is I think the design team just ran out of time trying to balance handling, ride quality, traction, and (yes) fuel economy. Ultimately they found a design that works well for typical street conditions, but as we now know, when you pushed the AP1 to its designed limits (and especially beyond, such as by using grippier tires), the car's response became highly nonlinear.

At the very least, all of this puts in perspective the car's much-vaunted "ideal 50/50 weight distribution": if it were so ideal, why did they have to resort to such huge differences in front and rear tires and suspension?

Mr.Matchbox

You are probably right. What came up to my mind is a question: We have different swaybars over the years fitted from the Factory.
But the Aftermakert companys wich produce Coilovers (Bilstein as Example) developed them in the early stage of the car, as soon as it was sold. The Bilstein maybe was developed using a MY 00-01 car?
Therefore, when you install a Bilsten in a - example - MY 07 S2000 it maybe is not working as "Optimal" as intendend by the Bilsten Engineers.
I am splitting hairs and counting beans, i know.

Car Analogy

The same situation exists with lowering springs for stock shocks. They're all based on spring rates and damping of stock shocks from the early cars.

Lowering springs are far from ideal. But less so on models that are farther outside their design environment.

As for coilovers, its easy to swap swaybars from earlier cars. Or better yet, use swaybars to further tune balance to your preference. Just because coilover maker decided on a specific front rear bias, that was based on early swaybars, doesn't mean you prefer that same balance.

Also, did coilover maker base their design on stock stagger, or did they assume they'd be used on track, and most buyers would already have gone square worh aftermarket wheels? Do their assumptions match your setup?

Jah2000

I doubt it was "wasn't fully sorted."
From what I've read in the past, the chassis/suspension engineers and r&d testers/drivers are all from F1 (for the NSX and S2k), and intentionally made the Ap1 versions of the nsx/s2k handle like a real true race car (not primarily for novices, not an easy to drive street car), super twitchy & floaty, stiff and uncomfortable, prone to oversteer and spinning out, etc. ...just like an F1 car - very hard to drive (without spinning out); but with ultimate throttle-control/steering for the more experienced drivers.

They then softened/tamed the suspension (spring rates, swaybars) specs/tuning after the first Ap1 versions, to account for regular street drivers.

Highline

Is my understanding correct that the sway bars are the last or final touch one would add to the car after suspension modifications and alignment testing? I heard this many years ago from race teams and it has always stuck with me. Or is the general view that it’s a matter of preference for the driver and their confidence?

twohoos

^It's not incorrect, but there's a big difference between a racecar and a street car. Swaybars are great for "sporty" street because they can reduce roll without adding (much) ride harshness. It's frankly a great compromise that makes many sportscars tolerable to drive on the street. The big drawback is they reduce the "independence" of an otherwise independent suspension. For the un-driven wheels, it's not a huge problem, but for the driven wheels, too much bar can lift the inside wheel in a high-g turn, causing loss of both traction and power transfer at corner exit.

For our car, the AP1 rear bars were fine for the OE Bridgestones, since you couldn't get enough lateral g-force to affect the inside rear. But above 1.1g or so, the torsen diff was overwhelmed and the inside rear (along with engine rpm) would simply spin up freely at corner exit as you applied power. Still, going slower isn't a catastrophe, right? Well it's what came next that was a killer: once the car started to straighten, the now-spun-up inside rear (wearing a super-grippy tire, natch) would drop and suddenly grip hard, sending a huge shock through the entire drivetrain. Basically the AP1 rear bars contributed to a ton of LSD ring & pinion failures.

For the AP2, the rear bar was softened and the diff housing was strengthened. That certainly helped a lot, but it's still quite possible to get inside rear lift. The only real cure is a full clutch-type diff, and/or removing the rear bar entirely. The latter forces you to use crazy stiff rear springs to recover some of the lost roll resistance. (A few clever track guys found a way to fit a particular Miata front bar in the rear, which greatly reduced wheel lift but still took some load off the rear springs.)

Highline

Awesome reply. New owner of an AP1 so I’ll be popping in with more questions.

Out of all the cars I have owned and driven on track, I have only ever changed one sway bar to a non-OEM version. I’m curious to see how this car handles at higher speeds.