Strike

I find this discussion very interesting, 'cause I've been using the stock S02's at the track since I started going to the track two years ago. I've become very good at controlling the car at or near the limit as time has progressed. I don't have the experience that some may have with cars and/or tires that are more forgiving but I can say with certainty that this car can be driven close to the limit with the S02's without worrying about constantly going off. My hope is that because of my experience with the S02's that I've learned to be that much smoother and when I start using race tires (soon!!) I will see the benefit of that experience.

pfb

While I do agree that the S2000 is *extremely* tire sensitive, not just to brand, but inflation and wear as well, I've experienced loose handling even with the A032R's.

Race tires are usually thought to have more of a "fast breakaway" than street tires, S02 included. If folks think that they are going to slap on a set of Kuhmo Victoracers and have less probability of the car getting away from them, I'd urge caution. Race tires, even with their higher level of grip, are known to be much more unforgiving when the finally do let loose.

frayed

In line with what pfb stated, when you look at plots of force vs. slip angle, R comps typically show a notably higher peak (representing higher cornering force), but the peak falls away much more quickly (representing fast breakaway).

The general rule is that even the most predictable R comps (eg, A032R's) have a higher peak force but fast breakaway than mega performance street tires. If indeed the OE S02 has a steeper dropoff than a Kumho or an Toyo, then I'd consider it a poorly designed street tire. . . sorta the worst of both worlds: less warning of a skid than an R comp, and less grip than an R comp.

This is why I doubt the fast breakaway characteristics of the S2k are purely a tire issue.

Prolene

"Racing slicks have a higher peak CF, but this best CF range is narrower in slip angles before it loses 10% of its grip, compared to street tires. Driver of a car on slicks would have to be more tidy with the yaw angle of the car under cornering.

In regards to peakiness, typically, a slick racing tire has a more gradual loss of grip past its peak than a street radial, making it more forgiving as you exceed the peak slip angle.

Today's high performance street radial tires are not all that peaky (where grip falls off dramatically), but as a rule they are worse than slicks."

The preceeding was summary/quotes from Going Faster 2001 pages 197-198. Notice that racing slicks and street tires are being compared. I would guess good R rated tires for the track would approach the characteristics of the slick. A CF with sharp dropoff is not desireable, and I too think the SO2s tend to have this sharper dropoff.

sfphinkterMC

characterizing a car as "oversteering" is like many overgeneralizations.....at a minimum its useful to divide the turn at the apex. many cars, almost typically(u will see), have tendency
to understeer before apex(vipers, F1, etc), essentially all high powered cars will yield power understeer before apex, and power oversteer AND trailing throttle oversteer after apex.
the deal is all understeer and oversteer is a response to the DRIVERS input upon a particular chassis and turn, therefore it must always be addressed by the drivers car control....regardles of chassis adjustments or what car you are in, just as in a track event or race where your tires go away and the handling balance changes u need to adjust YOUR imputs to maintain the best(most efficient/fastest) path around a turn.
also from 5/10ths to 9/10ths the handling of the car is somewhat meaningless, unless uncontrollable, to the seasoned driver as it may have no reflection on handling balance at racing speeds. the S falls in this category and behaves more like a race car, driving below limit doesn't predict what approaching it does, so it "surprises" those not appreciating that.
finally, i believe what make the S difficult at the limit is its inherent relatively more pronounced bumpsteer, which yields that uncertainy while cornering, the inability for the car to take a set. all the other attributes complained about (sticky OEM tires, low polar moment, RWD, etc, etc), are actually gifts that make it such the great drive it is.

frayed

Odd, b/c Fred Puhn's book How to Make Your Car Handle shows the opposite relationship b/t cornering force and slip angle for racing slicks vs. street tires; racing slicks having a much sharper dropoff than streets. Could be an improvement in technology since Barber's book is more up to date.

frayed

Hey guys,

I was on the phone with the owner of Ground Control, who I'm on pretty good terms with, regarding some suspension issues on my M3 (they custom built my setup). They have recognized the stability issues with the S2k, and pointed a multiple items with the stock suspension setup, and have engineered solutions (street and track) to better balance the car, improve stability, while maintaining all the positive handling traits of the stock S2000.

I do not know all the details, but you may want to call GC and talk with Jay (if you can get through to him, may be tough). I do know that the high pressure gas shocks in the rear have been the the cause of some issues, as the compression damping is out of balance with the front, and they ramp up in rate too much under certain conditions.

Rumor has it that some of the Honda engineers in the US have been lobbying for some suspension changes (in line with what GC has recognized) but Honda has to date elected not to implement the changes.

FWIW, just thought I'd pass the info along.

Jeff

ultimate lurker

Just a comment on the A032Rs. I found them to be much easier to slide "safely" than the stock S02s. I found myself drifting the rear end coming out of turn 1 downhill at Streets of Willow when we ran Speedventures there counterclockwise. I was able to do it lap after lap. OTOH, they heat cycle way too quickly, and the rears were worthless after 1 day at Laguna and 1 at Streets (although my tail out style at Streets, and the torturously tight turns might be part of the problem :-).

I haven't had a chance to track my RA1's yet (I'll be doing that Friday after about 1000 miles of street break in), but they're pretty predictable and grippy so far on the streets and canyons.

In either case, the 205/245 setup I run (stock suspension) understeers a bit steady state, but it just requires mild throttle application to go neutral. I prefer this setup as I find on/off throttle transitions the most tricky in this car. When in a corner and on the gas to keep the car neutral, impending slides are much easier to modulate (as opposed to getting completely on and off the throttle which is inherently destabilizing). I found that the stock S02 setup was pretty darn neutral, but as others mentioned, the transition to sliding was abrupt. Once sliding it was easy to control with throttle modulation and opposite lock, it was just getting there in the higher gears that was problematic :-).

UL

cthree

I totally agree with what UL said in his last couple of sentances as well as some of the other things said above.

S2kRob brings up an important element in dynamic vs. static grip but UL adds a little something. Besides static grip (which the S02 does way better than any other street tire) and dynamic grip (which from my experience and confirmed by Strike is quite good on the S02) the key element in "driveability" is in the transition from static to dynamic grip. This is what makes the S02 such a handful to drive.

As I said the S02 has an incredibly square profile and very stiff sidewalls. These factors contribute greatly to its excellent static grip characteristics. They do this by narrowing the transition zone from static to dynamic. If you were to graph this it would look sometihng like this for a "normal" tire: (not to scale)

|-----------------------------|---------------|-----------|

The left section is static grip, the center is the transition zone (lots of tire squeal) the right is the dynamic zone or "drift" zone.

As I've illustrated there is quite a bit of transition in a "normal" tire with naormal stiffner and a normally rounded profile.

The S02 on the other hand would look something like this:

|------------------------------------|--------|----------|

As you can see they have increased the static grip zone at the expense of the transition zone by making the profile square and stiffering the sidewalls.

On the street you shouldn't really be running in the dynamic grip zone. Most of your driving will be in the static zone. The S02 has a much wider static zone than a normal tire which makes them grippier on the street. You can drive 8/10s on the S02 with complete hold on the road. A normal tire might only offer 7/10s. At 9/10s you are in a drift in the dynamic zone.

How much grip a tire offers is based on its compound. How that grip is profiled in terms of the zones above depends on its design.

The thing to remember about race compound tires is that they have more total grip. Compared to the RA1, the S02 has about 3/4 of the total grip (in my estimation) of the RA1 in peak form. If 10/10s on the S02 is 0.92Gs then the RA1 would have a 10/10s grip of over 1G. That means that the forces acting on the tires and suspension are greater at the limit resulting in greater consequences if you screw up.

Bieg

This car as well as any other well ballanced sports car is DESIGNED to be powered through a corner. That is how you are SUPPOSED to drive and if you don't know that you shouldn't be driving fast to begin with. Coasting through a corner at too high a speed proves NOTHING.

Maintain a constant radius and apply power (ala SKID PAD) and you will see you can control the car easily with the throttle.