Hi,

I've been experiencing an issue with what feels like the rear of the car, where it become unsettled while cornering. It feels like the rear of the car shifts while cornering, and more so if I hit a surface irregularity while cornering, almost as though theres a large weight moving from one side to the other.

I'm getting used to it, but it "unsettles" me a bit when I feel it. Theres maybe a thousand miles on the new tires now. Is this expected? What should I be checking?

It was in the shop recently and I had the following done ( in order )

2 months ago:
Ride height adjustment (Brought up, theres about 3/4" between tires and fenders now)
Set preload (TEIN Flex Z Coilovers)
Attempted alignment - could not break loose tie rods; No alignment changes

1 month ago:
New tie rods
Replaced Hankook summer tires w/ Bridgestone Potenza S04s
Alignment (OE 2002 specs)

3 weeks ago:
Set TEINs to about middle damper adjustment, which feels comfortable.

 

Are you letting off the throttle mid corner? That's a textbook way to induce oversteer in any car.

S2000's (AP1's especially) have a pretty steep amount of bumpsteer. So they're going to react more sharply to letting off the throttle mid-corner.


What alignment spec did you use, and what year is your car?

Did the issue become more pronounced after you changed something?

Why did you need tie rods? What tie rod did you go with?

You said you set preload. To what setting?

Was your alignment done after you made all your changes? Or did you change it after the ride height...and then install tie rods/change preload/get tires/etc?

 

It seems to happen on and off throttle. I'll keep it in mind next time its out.

The shop should have uses the OE specs for 2002. I have the alignment sheet.

I noticed the shifting/unsettling of the rear after the new tires.

The driver's inner tie rod was galled up and I couldn't adjust it; So that inner and both outers were replaced w/ OEM.

The TEIN preload is perch contact + 1/2 turn or so from what I understand; I need to confirm thats what the shop did when they set the height.

All that said, I didn't noticed the issue w/ the rear until the new tires. I was assuming it was the tires but figured they would have broken in by now.

Also tire pressure is 36psi all around.

 

Well, was the alignment done after all your changes? Like...tires and alignment on the same day? Tires after alignment...? etc

 

Sorry it was a bit vague, I updated my original post.

Ride height, preload > Tie rods > Tires > Alignment

 

Do you have the alignment sheet? This car is very temperamental towards poorly done alignments, if the shop didn't do it well its going to effect the handling.

 

^yep,

based on that, the alignment could very well be the culprit, since you got it after/same time as tires.

 

Some parts I would suggest you look into:
- Spoon sub frame rigid collar kit
- Spoon rear control arm bump steer kit
- Spoon rear lower ball joint bump steer kit
These all require an alignment after install.

 

Thanks, attached is a copy of the sheet.

They did say that rear-driver side eccentric bolt was seized, and front caster adjustment was limited, though everything measured within spec. I opted for a little more camber but its close to what it came into the shop with.


I'll take a look but I wasn't looking at modifying it much more. Its pretty much stock except for the coilovers / exhaust / intake. I was thinking of replacing the bushings w/ OE or Hardrace if they are suspect.

Alignment sheet; Some values had to be edited in since the original had values too light to scan.

 

The rear geometry of the AP1 was always a bit compromised, and caused nervousness across midcorner bumps. You'll hear people talk about "AP1 rear bumpsteer" (rear toe changes as susp compresses), but that's only part of it. It's also due to the rear roll center height, and, particularly, the large/stiff AP1 rear swaybars. Remember a swaybar inherently reduces the "independence" of an independent rear suspension, and the stiffer the bar, the less independent it gets. Besides skittishness, the stiff bar can also limit traction at turn exit. It's so pronounced that some S2000 "track guys" have gone so far as to replace their rear bar with the front NC Miata bar (less than half the stiffness of the softest OE S2000 rear bar), or even remove their rear bar entirely!

For '04, Honda significantly reduced the stiffness of the rear bar, and also revised the rear upper arm linkage locations, which both reduced bumpsteer and lowered the rear roll center. Even neglecting the other changes to the spring rates, this makes the AP2 (and "refreshed" Euro/JDM AP1) much better behaved at the limit.