You really don't understand because I never insisted on my current setup being the best or any good for that matter. I said I would like to get matched tires (Z1s) all around but first I have to sell my current tires. I also said I am getting a stiffer front sway bar and do an alignment with probably the UK specs.
I'm also running numbers on aftermarket springs to see the percent of increased stiffness in the front and back in order to keep the same balance that the stock rates provide, just like I was advice. Like I said, I would like a bit stiffer ride all around, and a slight drop in ride height.

I did ask for a reason why the tires in the front should be 205mm wide in the front and whether it is better to have a thick or thin sidewall on tires for performance driving.
Personally, I would think a wider front tire would be better (225) but I don't have as much experience as alot of guys here. I personally don't have enough experience to know first hand what would be better here. As for the sidewall thickness, I don't know, and would like to understand what is better and why.
I appreciate the advice I have received but I would also like to know why it is what it is. Like many, I like to know the answer to why or how something works and why something is better than something else.

Just because I ask for an explanation doesn't mean I don't agree or I brushed off/ignored the advice given.
I ran the numbers on the CR/early AP1 springs and it changes the balance significantly from stock so I'm not getting them anymore.

Do you understand now?

 

I suggested 205 front because you can't get the correct 225/245 combo in the Z1 and RE-01R tires. If you run the RS2's you can run 225/245 but the car will be oversteer prone without a front bar. As far as sidewall typically you'd want something lower if you want less sidewall flex and better cornering response but not at the sacrifice of using incorrect sizes (try and keep the same OD). I've had really good luck with the 205/55/16 and 225/50/16 RE-01R combo on the S2000 and am running the 205/50/16 and 235/45/17 Z1's on my Elise currently.

Typically the S2000 oversteers, running a wider front tire and a skinnier rear tire (respectively) will probably not give you the most stable setup with stock suspension. If you run less of a stagger like 225/245 you'll probably want a large aftermarket front sway bar. Either way get yourself a good autocross alignment first, it's the cheapest and can make a big difference. Next get some good matched tires and lastly work on suspension (I'd try an aftermarket front bar first like a whiteline/cusco) and then shocks and springs.

 

Thanks CosmosMPower

For now, I'm going to do an alignment with a larger FSB.
After that, I'll get Z1's all around or get 2 correct OD 245mm RS2s for the rear since it would be cheaper to buy 2 tires.

 

Don't get me wrong, the RS2's aren't bad tires at all just not as fast as the other 2 but completely acceptable for track driving. I think 2 rear tires, a cheap front bar (find a used one even) and alignment is the way to go and will greatly improve your car for less than 500 bucks.

 

sounds good to me

 

I think most here would agree that cross drilled rotors wouldn't be considered an upgrade, especially for track driving. Best to stick with OEM or Brembo blanks...

Pads & Tires. Don't waste money until you've got to grips with the car and you're consistent. I know it's tempting.

 

whats the best source for the white line sway bar?

Is it better than the cusco 32mm?

I have a bone stock 03 S2000 on BFG R1's.

 

They are actually only slotted, not cross drilled. I just realized as I replied here. I agree with you though. The previous owner put them on the car anyways, as well as the pads. I don't think slotted is as bad as cross drilled in terms of taking away braking area from the pads but I'd have to spend money to put anything else on em.
IMHO, I actually think they are better than the stock non-slotted because I haven't experienced any fading whatsoever with them. That's not the case in my previous S, which was 100% stock.
It could just be the different pads

I really like how the slotted rotors look too. For me, it's a freebie.

my bad

 

It's not the surface area, it's the durability. If you actually start driving hard enough on the track to fully use the braking capacity, you will crack the rotors. I guarantee you those rotors will crack right down one of the slots.

At that point, you should replace them with stock rotors. Not only will the solid surface last longer before cracking, but they will be cheaper to replace in the future.