I recently purchased a 2004 AP2 with bone stock suspension (50k miles) and stock wheels (215F/245R) on PS4S's. I took it to autocross and I was able to get the rear out quite a bit after some practice, and going again in a couple weeks, but generally I've found that the car loves to understeer stock. On spirited drives as well, I've learned to get the car balanced and not understeer if I don't want it to, but I haven't quite figured out how to make the rear loose grip, unless I enter a turn too hot. By the end of 25+ laps in autocross the rear was very willing to kick out, but my guess was that was due to tires getting greasy / shredded or increased tire pressure.

What's the easiest way to introduce just a bit more rear-end liveliness / cut out some understeer on the car?
Bump up tire pressure? Alignment? ap1 rear sway bar? thicker front tires? Would switching to a 225/255 help, or would it keep the same balance?

Or is it just driver mod? Feel free to roast me if that's the recommendation

 

What's your goal, fun or faster? I fully understand fun.

Shamelessly plagiarized (and not fact checked): If understeer is faster for non-pro drivers, why do so many non-pro drivers believe that oversteer is faster?

• If oversteer was faster, the 1000 hp drift missile at your track day would set FTD. But instead it’s a Miata with too much wing on scrub SM 7.5 tires.
• If oversteer was faster, F1 cars would rotate through the majority of corners. But they don’t. You see more F1 cars push the front than the rear.
• If oversteer was faster, people would put wider tires on the front than the rear. But they don’t. High powered cars run a staggered setup, or maybe square – but you won’t see a RWD car in a gorilla stance.
• If oversteer was faster, you’d see cars with more front aero than rear. But most race cars are split about 1/3 front and 2/3 rear downforce.
• If oversteer was faster, Spec Miatas would have more oversteer than a stock Miata. But SMs have a 63% front roll couple, compared to a stock Miata’s 59%.
• If oversteer was faster… well, you get the idea. It ain’t.

If you think oversteer is faster than understeer, I want to see your data.

-- Chuck

PS: Here's the article: https://occamsracers.com/2023/07/14/...han-oversteer/

 

Good question! I'm looking for fun. I know oversteer isn't faster (though it may feel like it).

Just looking to hang the rear out a bit more often for enjoyment

 

Easiest way, adjust tire pressures. But that will have small effect.

Another way, thicker rear swaybar (or thinner front). There is no thinner front than yours (thinnest stock, and aftermarket all thicker). Thicker rear is as simple as getting a '00, '01 rear swaybar, the thickest stock one.

Or a '02, '03 rear bar, second thickest.

To see impact this would actually have on your specific cars balance, and compare it to each other years stock balance, I created a suspension calculator. Just mix and match stock swaybars from other years, see effect. Or swap springs from other years, see effect. Or swap aftermarket stuff, see impact. Pick parts based on data, not guesses.

My '06 has similar suspension specs to your '04, and I also hated how understeery it was (fun street car, don't care about lap times). So I used calculator to plan my mods.

Where I landed was swaybars, and lowering springs. Not to lower, but for their spring rate. Turns out virtually all lowering springs based off ap1 spring rates, as that was only model available when these springs were designed. So they all move balance rearward. Soke much more than others.

I didn't want car much lower, so chose springs w least drop. H&R. .5" rear, .75" front. Front ended up too low for my liking, so fabricated a spacer to go under stock spring perch. That would work on rear too if you wanted. Created a thread on it.

S2000 suspension spacer

My suggestion. PM me your email address, and I'll send you calculator. Plug in different swaybars in calculator, see effect. Buy whichever rear stock swaybar seems right, try it out. If still not enough, plug in springs, see effect. Decide which ones, buy, install (clock bushings!!!). Decide how much higher you want them to be, make spacers (use motion ratio to figure out how much spacer equates to how much lift).

Alternative to diy spacer, buy shock coilover adjusters. These are hollow threaded tubes, slip over stock shock in place of lower perch. Allow threaded preload adjustment on stock shocks (which you'll use as a ride height adjustment). Exactly like an aftermarket coilover shock.

 

Thanks for the suggestion!

And it seems like swapping tire sizes is not a suggestion of yours, mainly springs / sway bars (makes sense). Any reason you don't think tires would have an impact?

and PMing you now!

 

What about going square?

I kind of thought about that for the track, as I also find the car a bit understeer-y on the track. But this means finding another set of AP2 wheels or at least 2 rears... and then apparently some sway bar adjustments/replacement?

I didn't go too far down that road, though. A car that tends towards understeer is safer for me at my current skill level

 

Quickest and cheapest option - AP1 rear swaybar or eibach rear sway bar (it's stiffer than any of the OEM swaybars).

Next biggest and most impactful step - square wheel and tire setup. 255F&R or 245F&R on a square wheel setup of 8.5 to 9.5" wide. It will be more impactful and cheaper than any worthwhile coilover upgrade.

Plenty of 9" wheel options if you're willing to roll fenders, anything +45 offset and up with 245F&R will fit easily. If you don't want to roll fenders, will need to look for wheels +55 and up.

 

Does it make sense to go square AND add a RSB? Generally I’ve read that people add a FSB with square to neutralize the front grip increase relative to rear?

 

I definitely wouldn't do both at same time. One, then the other. Baby steps. Single change, eval impact.

But gut says you're right, both will be too much.

Keep in mind wider in front reduces steering feel, already biggest weak point of our chassis. For track its more about lap times, and gain is worth more than what is lost. But street, and perhaps autox, its more about feel. What is lost is more than gained going square.

I would avoid square if not doing track.

 

Yeah that’s what I’m thinking as well.

By the way, eagerly waiting for your calculator! I’m thinking to just put an ‘03 rear sway bar on, and see how it feels.