murderedrsx

Someone measured a toe curve here but it lacks some data (I just scanned the thread, maybe its there)

Found this too which is off topic of bumpsteer and toe curves, but is a very interesting read.

My link

User 121020

Take that "comparison" with a grain of salt. There are too many uncontrolled variables - AP1/AP2, wheel sizes, aero/non aero, power modifications, weight reduction, etc., etc. The lap time comparisons and "conclusions" should be ignored.

The damping curve shapes and adjustment ranges are interesting, but even those lack units.

mLeach

if all you're looking for is the delta, you can tape a laser to the face of your brake rotor and move the shock through it's range of motion. Start with your normal ride height distance from lip to center of hub, and move it up and down. plot the movement of the dot relative to a vertical line that passes through the origin at ride height. done.

murderedrsx

Nmrado. Yeah i thought the same thing when i glanced it over, although its still interesting and does provide bits of insight.

glagola1

Yeah, I saw that article when it came out. It's really bad journalism. To even publish that article shows that SCC doesn't care and they cater to the mildest of enthusiast. What it does show is that you can't go faster simply by bolting on some shocks.

User 121020

Exactly. There is some info that isn't garbage, but the main takeaways shouldn't have anything to do with the lap times between the various cars. It's just too uncontrolled.

glagola1

A meaningful article would have had 1 car. All shocks would run on that car at the same ride height and with the same springs and each shock would have been adjusted to find the best settings for that track.... but really, how could that be done all in one day?

Forcednduckshn

I agree Matt. I was surprised I could not find it readily available.

Rob R and I chatted a bit via PM on the topic. I don't want to violate forum rules by posting a link to hondatech (is that allowable?) but you can find this there. It's not a toe curve but it's better than nothing. This was technical data posted by Honda:

""2004 And Up/ AP2

• One of the "features" of the outgoing (AP1's) S2000's rear suspension was its tendency to exhibit bump steer at the limits. Honda's engineers have attacked this issue from several angles. Rear toe in (Alignment setting) was reduced from -0deg 19' to -0deg 10'. At a 50mm bump deflection, toe-in has been reduced from -0.19 (AP1) degrees to -0.05 degrees (AP2) Secondly, the rear roll center was lowered from 101mm to 92mm. Honda claims improved roadholding under full suspension compression or during severe body roll situations. ""

50mm is a little under two inches (1.968" to be exact). If nothing else, you can get a good, numerical idea of how dynamic the toe change is in the rear of the car. Simple math, -.05 / -.19 = 26%, or in other words a 74% reduction in maximum "toe gain" in the AP2 rear geometry vs. the AP1. For those that have driven both platforms, the difference in feel and stability is remarkable. There have also been evaluations done (a best motoring video comes to mind that analyzed differences between AP1 and AP2) that would "strongly suggest" the AP2 rear geometry equates to high cornering speeds because of the added stability, particular at corner entry when the rear of the car is most light. Not bashing the AP1 (much love for it) - just stating for reference.

The AP1 geometry seemed designed with a heavy bias to "trying to elminate understeer at turn in/corner entry." Crank in a lot of toe-in to combat this, and voila', the stock recomended alignment setting of 1/4" total toe in seems to make sense.

glagola1

Yeah, this bump steer is what makes the AP1 work and the AP2 a little "dead" feeling. You want the car to turn in so you ask for a little toe out under deceleration. Then when you get on it, you want the rear to toe in to enhance stability. I don't see why this is bad and obviously, neither did the original designer of the S2000. It's when consumers complained of the "twitchiness" of the rear over bumps that we lost the dynamics originally bestowed to the chassis.

This dynamic is what made the AP1 special IMO. As soon as I purchased the AP1 and took it to it's first auto-x after owning and developing my 2006 during the 2010 season, I realized that it was sorta special. Even on the crappiest all season tires, it possessed some magic. This magic manifested itself in a tight chicago box. I came hauling butt into the entry and braked. The rear came loose and pointed the car in the right direction and as soon as that was done, I stomped on the gas and it hooked up and shot out of the element. In the AP2 this action wouldn't happen and was a massive source of frustration for me. I'd tune the suspension so that the car would turn in and then the back would be loose. If I made the rear stable the car would simply understeer. There seemed to be no perfect middle ground which I thought was impossible since I had a few years experience in the AP1 back in the B-stock days and I thought that car was perfect.

Anyway, these are just hypotheses. Perhaps they explain why the lighter and more powerful CRs aren't the overdog they should be on paper.

Forcednduckshn

Yeah, there is no car I have ever driven that feels like the AP1 in the back. The fun factor is off the chain with it. I think if you can master controlling the rear of the AP1 in all parts of the corner, it's a skill set you transfer to any other F/R platform out there.