gptoyz

No joes racing tire pyrometers are like $100 on amazon

Don't get one of the surface IR scanners you need to know what the tires carcass temps are

gptoyz

It's all about balance.

The ap1 early model was already tail happy
Then you added a square setup which of course means now you will lose the rear before you lose the front so now you take the staggered tail happy car and made it even more tail happy.

By changing to and ap2 bar, you will increase rear grip balance allowing the rear to squat down. Yes you might get more rear roll but again I think your geometry is a little messed up. Also it's plug and play and cheap! Later on you can decide if you want to go with a stiffer adjustable rear bar but you already have the early ap1 bar.

Also if you are going to change the rear bar might as well toss some Delrin or poly hard bushings - actually you might as well toss on poly sway bushings everywhere.

With the amount of miles on your chassis, I'd also consider Megan engine, transmission, differential hard rubber mounts and spherical to replace all your rubber bushings.

Bruunz

I'm really suprised by the high numbers, i was told AD08Rs worked best around 32??? - How to set "hot tyre pressures" in Neova AD08s and ADVAN race tyres | News & Blog

What i might try next time is running staggered pressures. I've always been aiming for 32 all round. I might try running more in the front. If its too much it should create understeer but i guess thats what i want so i can figure out how the tyre sounds at max grip levels without facing backwards.

Bruunz

OK - Got my ride height measured roughly. Definitely was not able to check LCA to ground. Don't know why i thought i could even get under there...

The ground i was on is not 100% even - Very slight slope to front right. Enough to make the car roll forward in neutral. Front guards have been reshaped too so might have to remove a a tad from the front. Maybe 5mm at most.

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

Will update main original post with these figures

Bruunz

Update:

So I had another track day last weekend and conducted a few tests.
My goal was to have 34SPI front and 32PSI rear all day to change the bias of grip.
I did purchase a tyre pyrometer however it is still somewhere in the pacific
One thing I noticed is my tyres don’t 'sing' approaching their grip limits and only occurs after the limit is reached or not all when it comes to understeer.

Session 1:

Cold morning, about 10C Air temp.
Quite a foggy morning too however track looked dry.
PSS 9 Stiffest setting front and rear.
Cold tyre pressures:

FL FR
30 30

28 28
RL RR

The car did not feel very good to drive, it removed a lot of confidence when driving. It basically felt like on a knife's edge.
I had instability before and after the apex and I struggled.
Somehow I knocked out a PB of 1:05.5 before I caught some traffic which surprised me.
Under breaking the car would squirm around in the rear. I felt slow yet somehow I was quick.

Hot tyre pressures:

FL FR
33.5 34.5

32 34
RL RR


Session 2:
Lunch time after missing the real 2nd session because the immobiliser decided to lock me out of the car whilst my keys were in the ignition...
I must thank my father for bring me my spare keys.

PSS9 Front Stiffest Setting
PSS9 Rear set to 5 which is the middle setting.
About 22C air temp

At this time of day, the track felt greasy and I didn't feel fast at all. My lap times reflected this.
What I did notice was my car felt comfortable. It was the first inkling of understeer I have experience in the car.
It was very minor however over steer felt predictable and occurred at a slower rate. On the flip side, I felt the car was the lacking steering response.
Everything I did seemed a little delayed but also the car was delayed which meant oversteer was easy to manage.
I did experience a 'death wobble' at about 2min mark in the video. Very uneasy feeling and wouldn't settle unless the car was going straight.

Hot tyre pressures:

FL FR
35.5 36

33 34.5
RL RR


Session 3:

Like the second session however it got a little cooler as the sun wasn’t directly above us anymore.

PSS9 Front Stiffest Setting
PSS9 Rear set to 5 which is the middle setting.

I forgot to measure hot pressures but there was almost on 34PSI front and 32PSI rear when hot.

With the tyre pressure closer to what I was aiming for, the car had a similar feel to session two however I knocked out another PB which literally few hundredths quicker than the first session.
The car still had the slow response which felt easier to drive but I felt slow.
Under steer was starting to appear more and more at the hairpin at the bottom of the hill. Then the bane of my existence appeared... traffic.


Session 4:

This was the fun session late in the afternoon. Traffic was my main issue.

PSS9 Front and Rear set to Stiffest
Tyre pressure were spot on 34PSI front and 32PSI rear hot.

Having the rear back to stiff with the PSS9. I felt the sharpness return to steering inputs. I think by the end of the day my tyres were on the way out.
Traction seemed to be limited. As seen, I get a lot of understeer at the hairpin where it reminds me of a FWD then it switches to an over steer.
I became comfortable with oversteer by this point in the day. So confident that I actually become cocky on the last lap and lose it
The last lap would have matched my PB if it wasn’t for the spin on the finish line.


TL; DR
So hopefully I understand this well enough…
I wouldn't like the feeling of a softer rear bar because it would make the steering a little sluggish.
I need to increase the stiffness bias to the front?? I guess the best way to do this is get an FSB?
Is my thinking heading in the right direction?

s2000Junky

I would get a stiffer bar up front. Not only are you trying to re bias the car to plant the rear more, but you need more spring rate to tighten the car up so you aren't floating around so much. This kills 2 birds with one stone. Removing rear bar will achieve the bias you want, but remove spring rate so that's the wrong direction to go.

Apex1.0

I have also thought the sway bar package in the 00-01 is pretty good. As you add grip and drive more aggressively, the overall wheel rates need to increase for both roll and pitch. The spring rates and in turn damping rates in the PSS/PSS9 are too low for aggressive track driving IMO. You can surely go fast with that setup, however you want it to feel good also. When you get it setup right you should not have to work so hard to be fast (for you) and consistent.

With the right damper package you can run spring rates over double from stock and actually have a better street ride. My 500/500 Koni GC setup was very consistent and predictable and felt good with 200TW tires. However if I did it again I would have gone with 550 or 600. The koni yellows have a tremendous amount of rebound damping available. Thats the affordable option, KW or custom or Ohlins would be the more expensive option.

The correct spring rates and a good damper wont necessarily add speed all by themselves, but they will add consistency and predictability. You will be able to apply the available tire grip with less drama approaching the limit. A well setup car should be almost boring to drive at first. Then you can add speed with confidence.

Otherwise, you may want to add a BSK. If not limit your rear toe to about .30 degrees total. Every time I reduced the rear toe, the feel has been improved.

Lastly, the S2k loves to trail brake. However if you are trail braking every corner to get rotation, something else needs to be addressed. A little more front grip may allow you to get on the throttle sooner. One thing I will say about this car is when setup, it will absolutely not bite you are long as you are on throttle.

s2000Junky

To further add to Apex1 last sentence, probably one of the bigger realizations about driving this car properly fast with little drama at the limit, is putting the gas down settles the car and makes it work, but to the inexperienced and or timid, lifting is the natural tendency when the car starts to over steer or do something unpredictable to the driver and more times then not, that is the exact opposite thing to do. Firming up the suspension in spring rate and damping limits the body movement and erratic shifting of weight of the car which makes unpredictable to the driver. The spring rate needs to be mated to the tire grip, so that the grip is maximized, yet the driver is able to focused on driving that tire to the limit, rather then trying to control a loose or verge of out of control chassis. **The driver should be focused on line choice and driving the tires, not the car.

Bruunz

Thanks for the input and i think i understand what you both are talking about. I know i have been driving the car to a particular line and it doesn't feel very aggressive. My lines are a little shallow and turn in is a tad early but i can manage to rotate the rear under heavy breaking. This line feels slow so i have been rolling on the throttle a little before the apex. I interpreted this as driving too slow but couldn't change the line or behavior confidently. I guess that is letting me drive faster out of the corner and ultimately learning to control the car under throttle.

I think i will get a Whiteline FSB as a stop gap and possibly look at some rear bump steer kits.

What do you think i should do with my ride height? Get back closer to 14" and reduce the amount of rake?

s2000Junky

I would suggest doing one thing at a time. In your case probably the front heavier sway bar. If your running taller ride height on one end of the car, your going to transfer more weight to the lower end of the car. In margin this can help tune a preferred handling, but with such a balanced car, id suggest running even front to back at a good place to start/work from, unless you have really honed in on what it is you are trying to capitalize on there. I run about .2" higher up front myself, which isn't much, but its enough to help transfer my weight balance to be rear heavy at 50.5 to 49.5, which I prefer for higher speed stability and general car control dynamics. I dont run a rear wing so it just further aids in planting the rear of car with a big rear tire stagger. My sway bar is also biased to heavier up front with a factory 00-01 bar and softer factory ap2 rear bar. Same spring rate f/r though. 14" is generally pretty high, most run closer to 13". But they also typically run firmer spring rates at that ride height as well which helps stay off the bump stops. With your spring rates, lowering the car more may or may not prove to help you. on one hand it would likely limit body roll, because you will be on the bump stops more, using them as the spring, but that can also be bad news for traction and could cause premature break away of the tire. This is where some trial and error on your part could be helpful. You dont really want to be on the bump stop in the corners, unless your tuned for it with typically R comp level adhesion.

There should be a good understanding of what you are doing when you are tuning your chassis, rather then just shooting from the hip or following what others are doing without understanding why so thats where I try and give some detail in why I do what I do or why I recommend what I do, like some others here. But some driving experience/trial and error is still part of that for yourself. There is a very general good set up for the conditions, and the rest is personal preference, so in that respect there is no single best, only what allows you the driver to achieve your best, what make you feel confident in your car. Getting the car to run predictably is probably the most fundamental first step. I have kind of strayed away from more typical set ups, addressing things as I find their weakness with a lot of trial and its been really fun to go down that road, and as a result I think ive ended up with a better performing car for me. Still always seems to be something here or there I find to still tweak though. Some of that is just the fiddler in me, which will probably never stop.

When i get bored of the current grip levels, and decide to get into big tire R comp levels, then I will have to go through another chassis tuning/modification round to support that and start over from square one in some respects, so not in a big hurry to go there.