Hi

I am looking to get some advice on what upgrade to do next. Any thoughts appreciated (I couldn't decide if this thread should be here or under racing n comp).

So here's my scenario:

2001 AP1 without about 195K KM /120K M on the clock,
The car is my only vehicle however its DD usage is quite minimal and sees a lot of time on the track. I would say its a 50/50 split.

I originally bought the car when it was slammed with big rims and low profile tyres. My intent was to track the car in stock form to learn its behavior before i started throwing bits at it. This was not financially feasible.
Instead i went for RPF1 17x9 +45 square with 200TW 255s to replace the crap tyre and rim combo and got myself some PSS9s. I know this isn't stock but for cost wise it felt i was money well spent. I'm especially happy to find out everyone seems to think the PSS/PSS9 is a good OEM replacement. Hopefully they have a provided a good foundation for me to learn on. Everything else is stock basically.

I've been on the above setup for 2 years playing with alignment and ride heights and have the car setup quite well is most areas.

As a DD, they car is great! I love it compared to when i first bought it. The PSS9s are set to full soft and i dont have an issues on bumpy roads other than being a bit low. I'm still on my original 200TW tyres and tread wear is great and even. I've only just rotated.

On the track however i feel like i hit a plateau early on and that my lines are dictated by the car and not what i want to do or try. PSS9s are always set to full stiff otherwise i feel like the car rolls too much.

Alignment:
Front Camber -2
Front Castor 5.9
Front Toe 0
Rear Camber -3
Rear Toe In 20' (minutes) of toe (half of UK spec)

I also run quite a bit of negative rake. (haven't measured it)

Ride Height:

Front Right Hub to Fender = 34.5cm / 13" 3/5 inches
Front Left Hub to Fender = 34.5cm / 13" 3/5 inches
Rear Right Hub to Fender = 32.5cm / 12" 4/5 inches
Rear Right Hub to Fender = 32.5cm / 12" 4/5 inches

Front foremost point of jacking point = 10cm / approx 3.9 inches
Rear point behind jacking point = 9cm / 3.54 inches

With the above alignment, the car feels good past the apex. Low speed exits are great i can now maintain full throttle with some counter steer with confidence.
Corner entry is finicky to say the least. I've started trail breaking and it seem i can only do it confidently in slow speed corners or a downhill entry. Anything flat or coming off a mid speeds is unpredictable and generally met with me facing the wrong way if i try to do it too much.
The best way i can describe it, is that i go from 80% to 120% a split moment after i have turned the steering wheel. Even when not attempting to trail brake, the rear never seems settled until after the apex (or when im on the accelerator).

During long turns i get a wobble sensation in the rear. In the videos below, you can see my counter steers. This is the wobble i get.

- 50 second mark of video (not lap time) is the wobble

- 45 seconds mark of video (not lap time) - this is feels like an exaggeration of the wobble. i dont know if its the uphill that causes it.

The rear feels like it wants to bounce out rather than step out in these cases.

The car does not under steer what so ever on a dry track.

Back to the plateau, i am now chasing tenths. I had a pro driver drive my car briefly and he wasn't very much quicker than me. He said that the turn in felt like a double movement. He would have to turn the car, wait for it to settle then actually complete the turn.

Now to my dilemma...

OK, so i originally thought that i have too much tyre / grip up front for the PSS9s and was going to get an FSB to offset it, most likely the whiteline one.
Then i started reading about how the PSS/PSS9 are too soft for track duty and they are good if they are rebuilt. Maybe i could rebuild them with stiffer springs?
On top of that, considering the age and mileage of car. I thought maybe i should redo all the suspension bushings?
Then i started thinking about an FSB again and the Karcepts bar came to mind. It would allow for growth if i got new coilovers.

Im now stuck in a rut. The only thing clear to me is that the whiteline FSB is the cheapest short term thing to do but would be a waste if i eventually went with the karcepts bar. Would i be ruining my DD with either of these options?

Im also based in Australia, so some options are not easily accessible.

Any thoughts?

 

Depends on how much money you want to throw at it.

I would get a less stiff sway bar in the rear. The cheapest solution is to probably toss an ap2 rear bar in.

Are you familiar with this thread:
https://www.s2ki.com/forums/alabama-...-rates-960657/

I would probably also get a rear bump steer kit. Basically it's like a giant rear toe arm.

To address your body roll:
How low are you? If you aren't using aero really not a huge point of lowering the car and having to correct geometry or roll moment. I would corner balance and raise the car to maybe some where in the range of 1/2 to 3/4" lower than stock so as not to disturb too much roll moment.

Alignment wise:
I'd probably increase front camber to get more corner grip and therefore get more corner speed also with that go for like a half a degree more caster. As far as rear toe, I'd probably bump the toe up to .6 total rear toe in.

Are you making sure you are getting the maximum performance out of your tires by using a pyrometer on track?

I'd see how all that goes before rebuilding your suspension - but that's always possible.

 

I would not bump up the rear toe, if anything I'd knock it down to 0.2 degrees total or 12' (arcminutes) total.
The "wobble" is an unfortunate feature of the AP1 due to the stupidly designed-in rear toe change with suspension travel (reportedly 0.3° per side per inch of travel!). For me, the wobble was worse and less predictable when I ran 0.64 degrees or 40' of total rear toe-in. When I dialled it WAY back to 0.15 degrees total (9') the car behaved more linearly.
Stiffer springs might help by reducing travel.
Bump steer kit should fix rear toe change issue altogether. There was one bump steer kit that had failures, but hopefully off the market by now. Perhaps someone can recommend a good BSK?

 

The biggest issue here I see is the spring rates are just too soft. I mean you can literally see the amount of body shift/roll in the vids which is nuts. Its more then stock. I had a friend on your dampers and they were super compliant/great feeling on the street like a caddy, which is not what you want on a road course trying to control a car at triple digit speeds. coupled with your improved over stock grip levels with extreme summers 255 all around.

I also have an 01 and the sways aren't bad on this car, actually the stiffest out of any of the years front and rear, so that's helping you to a point( could be worse) But the rear bar is indeed stiffer then the front coupled with a non staggered tire and you are already overly biased to over steer, coupled with a soft/vague suspension and its not a great combo. This is limiting you. I personally don't like running non stag on this car, but its workable with the right suspension set up which yours is not. First you want to go the other direction with the sway bars, more rate up front and less in the rear. I run an ap2 rear bar with stock 01 up front, its a good balanced combo with the right coilover spring rates for my tire stagger. You might appreciate an even stiffer bar up front to hold that rear end down to the ground forcing less over steer wile getting the benefit of a more predictable sharper turn in. Do things in increments. An adjustable front sway is not cheap, but non of the options are at this point other then picking up a used rear ap2 bar, but doing that alone will not do anything to address your mushy/vague handling suspension, but just make it worse. New spring rates all around in the 10-12k range either on your current dampers if they will work with them , or a set of new coilovers all together that will would be the next thing to do that will have a sizable improvement on controlling your chassis. So in order of cost/benefit front heavier sway (adjustable if possible) and or new stiffer coils for current dampers. If not possible to run on current dampers, then do the sway first. Running non stag tires on this car though, generally means you want stiffer up front and softer springe rate in rear. Sways are the best way to dial that in.

 

I didn't see your ride heights listed, but much lower than stock on those shocks is likely not giving you enough travel in the rear. It also looks like the car goes loose on throttle application after watching a few times. Honestly, a bone stock AP1 does this as well. I took my '03 to the track, and while the stock dampers are past their prime, with one that looks like it leaked out a while ago, the car is 100% stock as it rolled off the line with some "meh" All-seasons on it (previous owner).

The car is fun to drive at 8/10ths on track, but dial it up that little bit, and you get some odd stuff happening in the rear. I'm not sure it was bumpsteer in my case, so much as running out of rear travel in a few corners. Load the car up with a quick turn-in and get on the throttle aggressively and the car responds with a big WHACK of oversteer. Correct it, and get back on the throttle and the car feels great all the way to the exit of the corner. That momentary jump in rear spring rate coupled with the toe-out in the rear under compression upsets the car a lot.

Going into the same corner, at the same speed, with a much more gentle turn-in and throttle application resulted in no drama at all. So it's not bumpsteer, as statically the car felt good, it's just that transition to full load on the outside corner gave nasty surprises in the rear. Your car honestly looks like it's doing the same thing, but more often since you're likely lowered with similar to stock rates, and have grippier tires.


For me it was enough to make me not really want to do much more track time with the stock dampers, as you definitely have to tip toe around that in higher speed corners.

BTW - it might just be the audio, but it doesn't sound like you're holding the tires at their peak grip slip angle consistently in most corners. I'm sure some of that is you being a little tentative due to the oversteer, but you might try slowing the steering input down a bit and working on holding the tires at peak grip longer in a corner. It will feel less dramatic and slower, but I bet you go faster with your setup.


On trail braking - that's to be expected with a helical/torsen diff like an S2000 has. It doesn't bias across the axle on decel, so trail braking on the limit is tough to do because you can get momentary inside rear lockup and around you go. ABS is good at hiding the problem, but it still happens if you're truly cornering on the limit. My S13 track car had a helical diff in it, and it trail braked horribly due to this issue, and no ABS meant any lockup and around you go. Put in a clutch diff (Cusco RS), and it trail brakes absolutely beautifully. I probably picked up half a second on a 2 min lap just from trail braking much more aggressively in lots of corners and carrying that speed longer on the straights and rotating the car a bit better on corner entry. No easy fix there unfortunately, other than to say that most people use way too much brake pressure when trail braking. Try it again, but think more "ok, full braking at 100%, trail braking is 10% brake." You'll be closer in the ball park and can adjust. You want to be BARELY on the brakes as you trail it in. The S2000 has good ABS, so you should be able to greatly reduce the number of spins by being a little more gingerly on the brakes.


I'd recommend you raise the car up and see how it responds, and maybe think of upping the spring rates to keep you off the bumpstops as well. A lighter rear bar could be helpful as well, but I'd err towards getting more travel and going from there. You might also want to back off the damping a tad, max on PSS9's goes kinda wonky, and you might be trying to compensate for low spring rates with too much low speed damping, which gives some handling demons like you're seeing.

You might want to consider moving the front springs to the rear, and getting some higher rate linear springs for the PSS9's. That will give you a decent ~30-40% bump in rate in the rear based on published rates, and you can do about the same up front or maybe a tad more if you want to shift stiffness up there.

 

I'm really surprised by your comment. I didn't think i had a lot of roll when the i set the PSS9s to full stiff. i have the go-pro mounted on my chin so maybe you are interpreting my head tilt as roll.

Here is a really badly edited video of me at a skid pan event. The go-pro is mounted on my boot so it should give a good perspective of roll (yes, that is my interior missing because I'm too lazy to change the fuel pump and put it back together).

I know this isn't comparable to track work but it might help. Go to about 8min mark. I get a lot more aggressive.

 

They car feels a lot more predictable with less toe. I still have snap over steer in corner entry but i feel corner exit is a lot better with less toe. I can kind of feel the car squat and grip where as UK spec toe did not offer that feeling.

I'll add rear bump steer kit as an option.

 

@gptoyz @defsport

I don't actually know my ride height. I will try and get some measurements over the weekend.
I have reshaped front guards so i will try to get a few measurements for you. Hub to fender, jacking point to floor, and if i can reach i will try LCA to floor.

I was planning on buying one but they aren't cheap. I guess i should and this would probably lead into to Def's comment below.

I dont know what you actually mean but i am going to assume you mean tyre screech which would indicate that im at 10/10ths of grip.
I find this difficult to achieve. It will happen if i go above 32psi hot. 32psi hot is recommend for my Advan AD08Rs. This is where i chime back to having no understeer. I think you are right, the car is dictating for me to be more fluid. However i have had people comment that i turn in too early but i feel like a have to. I have to avoid aggressive movements to try and maintain momentum through corners.

Ill report back with heights soon.

 

Wouldn't putting an AP2 rear bar be working backwards in the scheme of things? Understandably i have a very conservative car but for a 50/50 car this seems like it would get replaced once i improve?

 

32 psi hot sounds too low for AD08's. I have had some friends run them, and they seemed to like the usual 36-39 psi hot that most street tires like. Bump up to the pressure 2 psi all around and see how you like it. I'll bet the car feels a bit more stable at high slip angles. Then do it another 2 psi all around and compare. Probably not a huge difference on those last two jumps, but I bet you'll notice the tire being more consistent over a session.

And yes, the tire should "sing" throughout a corner. You're only hitting that level a few times throughout the corner, and it doesn't seem very consistent. Make the car handle better at the limit, and it'll be easier to keep them at max grip. A loud "screech" from the tire means you exceeded optimal slip angle, which is bad, but if they're silent, you aren't cornering hard enough.