**Edit: I put the stock front sway bar back on and the car is very balanced now.

I went to the track with a new setup last weekend and experienced quite a bit of understeer on corner entry (and a bit on mid corner) on some of the lower speed, tighter turns. My setup is shown below.

2004 AP2
KW V3s (515 lb springs F&R)
Eibach 32 mm front sway bar (soft setting)
17x9 +45 RPF1s
225/45 front, 255/40 rear Hankook RS-3
J's Racing S2 camber joints
No wing

Alignment (corner balanced)
Caster: 6.75*
Front camber: -3.0*
Front toe: 0
Rear Camber: -3.0*
Total rear toe in: 3/16

Starting KW V3 settings:
Compression F&R: 2 sweeps (from full stiff)
Rebound Front: 4 clicks (from full stiff)
Rebound Rear: 6 clicks (from full stiff)

A couple things to note:
- I will be going 255 square when the current set wears out.
- I understand the rear toe in is a little higher than some like to run. Might this be a culprit of corner entry understeer?
- This was a lower speed track (75 mph avg), but I have a GTC-200 to put on soon.
- Car is used only for road courses, no AutoX.

The tire pressures were getting pretty high, but once I was able to get them to 36-38 psi hot, the front had a bit more grip. I also lowered the front compression by one sweep, lowered front rebound by two clicks, and increased rear rebound by one click. This seemed to help with understeer, but I definitely was not entering some corners as fast as I know I'm capable of. In said turns, I had to stay on the brakes on corner entry to get the car to turn in and the rear to rotate.

So I have a couple questions.

1. Should I put my stock front sway bar back on OR keep it and go with an AP1 or Eibach 29 mm rear sway bar?
- I like the fact that the Eibach bars are two way adj, but perhaps a rear sway bar might be too much when I go 255 square

2. What would be the main difference in handling characteristics with the two options when trying to reduce understeer: going with a smaller front bar or going with a bigger rear bar?
- Since the spring rates are not that stiff, I like the idea of having sway bars to reduce the body roll. But I don't want to reduce overall grip if I had to go with the stiff setting on the front sway bar when adding the rear bar.

3. Should I adjust the shocks a bit differently to address the corner entry understeer?

Any help would be greatly appreciated. Thanks in advance!

 

Everything will change with the added tire upfront.

I would not put the stock front bar on.

You will want to lower rear rebound not increase it. This will allow more weight transfer from the rear of the car to the front. You can also decrease front compression

 

Thanks for the suggestions!

So you recommend sticking with the Eibach front bar and stock MY04 bar, and then focus on adjusting the shocks?

With rear compression at 2 sweeps from full stiff and front compression at 3 sweeps, do you recommend going to 4 sweeps in the front? Do you think I should adjust front rebound (and which direction)?

I was unaware that I should have lowered rear rebound instead of increased it. I will give that a try. Thanks!

 

As you said, "quite a bit of understeer", personally, I WOULD swap to the stock front sway bar. Reason: it's an easy swap. The rear requires dropping the exhaust which can be a pain in the ass.

If it was only a little bit of understeer, I would agree with 762 and tweak the suspension settings and alignment.

In my opinion, you will need to go to stiffer front springs (~15-20% stiffer) once you go square on the tire setup. I see your square tire setup being stiffer front springs, your stiffer front sway bar, stock rear bar, and rear wing. Of course, to fine tune it to your liking, you'll have to experiment

 

Thanks for the suggestion. I have a light single exit exhaust, so I wouldn't mind the rear sway bar install. And the Eibachs are cheap enough. In your opinion, ignoring cost and installation, which of the two sway bar setups do you think would be optimal?

 

Going to a 255 square set up would definitely help

 

Dont put a stiffer rear bar on. If you want an improvement with the narrow front tire then dont let front tire pressurr go above 36-38psi hot and maybe put the stock front bar on. Adding more front compression usually reduces entry understeer. Try 4 sweeps on front compression then try 1 and see whats better. Reducing front rebound should reduce mid corner understeer but might worsen exit oversteer. Once you put a square setup on then go back to your baseline.

Less front camber might help in this case but it would b a waste to change if you are going to a square setup. INVEST in a probe type pyrometer to understand and dial in uour pressures and camber.

 

I recommend you leave the bar and springs as they are until you get your square setup on because everything will change with the wider front tires. I'm running KWV3s, 255x4, Comptech front bar, stock 2001 AP1 rear bar (going to try Miata bar), APR-GTC 200 wing, with 628 front springs and 571 rear, -3.5 camber front, -3 rear, front bump 3 sweeps, rear bump 4, front rebound 4 clicks, rear 6. Setup works extremely well with my driving style.

Really focusing on smooth turn in will help minimize entry under steer.

 

Thanks for all the replies. I will be doing a two day event at Buttonwillow in March, so I will have plenty of tuning time. I will likely try the stock front sway bar and save it for when I go 255 square I will post back with my results.

 

Also note your ride height. S2k has *lots* of bumpsteer in the front at low ride heights. A slammed car will understeer more than a car 1" lower than stock everything else being equal.