Holy Understeer!
 

Hi Guys--after installing the following mods, I've managed to create a massive amount of understeer which is killing my enjoyment on the twisties. After doing some research, the new (unfavorable) handling characteristic may be attributed to the large stagger between the front/rear tires. From what I've read, this could be remedied by increasing camber in the front and installing some sway bars. With the following mod list and suspension settings in mind, could anyone give me some solid recommendation for a street friendly way to improve the handling where the car is able to communicate every turn without plowing through it or kicking the back end out excessively?

19x9.5 +15 255/35 (f) 19x11 +13 305/30 (r) on Michelin PS4S
KW v3 set to middle dampening settings from KW--I like the ride quality on these settings so would no prefer to mess around with compression/rebound.
SPC front and rear camber kit
Whiteline front and rear Sway Bars with end links
Dropped down to two finger gap front and rear--would not like to go any lower.

Current Alignment Specs:
http://www.the370z.com/members/igota...65620301-o.jpg

I was thinking to increasing camber to -2 in front and keeping rear at around -1.5 to assist with turn-in.

In addition to the camber settings, which sway bar settings would you recommend on the whitelines?

I heard that soft front and middle rear is a good starting point?

Thanks in advance!

someone can chime in to help you with the suspension setup. but i dont think "massive" under-steer would come from the tire stagger.

if it was a bit of under-steer possibly. i have ran 265/35 and 305/30 setup for the last 4-5 years and the handling/grip is really good.

more negative camber
more positive caster
ditch the rear sway bar
more front tire
mebbe lower tire pressure in front

The rear end is just so darn grippy in corners compared to the front, which leads to the front not being able to communicate the turn leading to the 'pushing' feeling.

Would increased camber up front remedy this along with a full stiff setting up front on the sway bar and soft in the rear?

Anyone experience something similar when going with such a wide stagger?

You probably know this already but...

Make sure your tires are in good shape, worn front tires are going to cause you to understeer all day everyday.

Maybe look at this from a tuning perspective.

1. First choose the right wheel and tire setup
2. Choose your coilovers and alignment
3. Adjust your rebound and compression
4. Use swaybars to fine tune the handling.

If any one of those are off, like the first one...you're going to end up compensating for it elsewhere.

Stock stagger creates enough understeer at the limit that it's more than just a nuisance. Increasing that stagger is only going to further exaggerate it. You want to reduce understeer at the source of the problem? Go to a square wheel and tire setup. Any tire in my opinion over 285 is overkill for this car, especially if it's NA.

The car will rotate easier and you'll be able to control that rotation much better with throttle input. Anything else you do will be masking the inherent nature of that configuration. Although I know you said you don't want to mess with your compression and rebound settings. If you stiffen the rear it should make the car want to oversteer more and by that logic I would not recommend removing the rear sway bar as it will induce more understeer.

If you can...get a true square setup.
If you cant...play with your coilover compression and rebound but write down what they are currently set at so you don't lose that baseline.
Then...stiffen the rear a bit more from what it is now, maybe move in 1 or 2 click increments, see if the understeer has gotten better until you've reached your ideal setting.

If it's still understeering, maybe then see about setting up your sway bar to a stiffer setting. You are running up against your wheel and tire setup and I would not recommend you try to mess around with your alignment too much to try and fix this because your setup is going to be all over the place. Might as well start with the wheels and tires and do it right from step 1 onward.

Where is the understeer happening? Turn-In, mid-corner, or exit?

Thanks for the thorough explanation, however going with a different wheel and tire setup for the street is a no-go since I decided on the combo for a cosmetic approach, I will eventually have a dedicated track set for when I do start tracking. With that being said, is there a way to dial it out with camber/sway bar adjustments? At this point I’ll take the stock understeer feeling since the car was more responsive at the limits..

More noticeable at turn in; once in mid corner I have laid off the throttle enough to communicate the turn, but at that point all the fun is gone ;)

you should probably throw away the SPC stuff and get SPL FUCAs for full camber/caster adjustment

I think I have enough adjustment with the SPC parts. The real question is what settings to adjust to ;)

A valid point is that SPL FUCA allows both camber (static camber) and caster (affects camber as you turn the front wheels) adjustments, whereas the SPC ones that are usually mentioned only allows camber.

Given you said that tire size change is off the table, I would start with changing your front static camber to -2 degrees.

Oh, you really got a 21 incher? :roflpuke2:

Stock understeer more responsive? I drove on that setup for awhile and had no idea how bad it would understeer until i did my first track day. It was particularly heinous in the skid pad at Streets of Willow CW. That was anything but responsive to me, wheel completely cranked, full lock and the car would not turn, on throttle or off throttle.

Anyway, if you're not gonna bother touching your rebound and compression which is IMHO the easier and less expensive thing to do, then yeah...you have no choice but to try alignment and swaybar settings.

Try going stiffer on the rear bar and see if that helps. If not then you can try adding camber and toe. Toe out in the rear will make it want to oversteer, increasing camber up front will get you more grip on corner entry and should increase oversteer as well. Your camber settings will need to move up into the -2 and -3 territory to get the result you want.

Highly recommend the SPL stuff too especially if you have track aspirations.

Ways to Correct Oversteer
Lower front tire pressure
Raise rear tire pressure
Stiffen front shocks
Soften rear shocks
Raise front end
Lower rear end
Install narrower front tires
Install wider rear tires
Stiffen front sway bar
Soften rear sway bar
Reduce front negative camber
Reduce positive caster
Stiffen front springs
Soften rear springs

Ways to Correct Understeer
Raise front tire pressure
Lower rear tire pressure
Soften front shocks and stiffen bump
Stiffen rear shocks
Lower front end
Raise rear end
Install wider front tires
Install narrower rear tires
Soften front sway bar
Stiffen rear sway bar
Increase front negative camber
Increase positive caster
Soften front springs
Stiffen rear springs

I autox'd my Nismo '13 probably a month after I got it and noticed the major understeer. The tires that came with the car were "OK". They were Pirelli summer tires (don't know the specific type).....Anyway, I gave the car some camber up front and put on some RE71s and the problem went away!

All great ideas guys! I'm going to do my alignment this weekend with the sway bar install.

I'm going to try -2.0 (f) and -1.5 (r) camber settings with the whiteline sway bars set at full soft front; full stiff rear and see if that helps, unless anyone would advise against it.

Good full stiff on the front to reduce the understeer. I like no bar in the rear like Eagle stated. I would recommend just leaving the oem bar and try that setup and if that doesn't help the rotation then remove the passenger side end link to disconnect the rear bar and see if you like that better. If that does not work then you can add the Whiteline rear bar and start adding more bar.

Getting your suspension tuned properly is a slow stepwise process and you really only want to do one thing at a time so you know exactly what is working and what is not. One thing is for sure with the Z...you can't have too much front bar!

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Full stiff on front? I'm seeing two different trains of thought on this thread and throughout the forum. Albeit, everyone's car is tuned different, but is there some rational to this?

Ways to Correct Understeer
Raise front tire pressure
Lower rear tire pressure
Soften front shocks and stiffen bump
Stiffen rear shocks
Lower front end
Raise rear end
Install wider front tires
Install narrower rear tires
Soften front sway bar
Stiffen rear sway bar
Increase front negative camber
Increase positive caster
Soften front springs
Stiffen rear springs

LMAO, yes there are many opinions on this subject and you are free to pick which ever method you like but you asked for suggestions and recommendations so you got them. A few of us have been down this road and have received solid advice from others which include professional racecar drivers that also work on their cars. Eagle knows what he is talking about as he the fastest NA track day Z driver I know and I have seen his times drop dramatically since his last upgrades and tuning to his suspension.

Anyway, a soft setting on the Whiteline will be stiffer than the oem bar. Just be careful because it you get it wrong you can end up with snap understeer and that is about as scary of a mistake you can make with your suspension. Trust me as it has happened to me a couple of times during spirited driving and my seat has stains that can't be removed, lol. Good luck and keep us updated.

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I would really advise against full stiff rear, I would actually do the opposite. Heck I don't even run after market rear sways. Being full stiff rear is going to make the Z very very unpredictable at the limit, sure you might start to oversteer not but it's not going to be the fun type, it's going to snap at you

if you have camber arms then I would actually go even more negative to like -2.5

Found this Gem in another thread; looks like a pretty comprehensive guide into suspension tuning:

Car Suspension Tuning Guide| Rapid-Racer.com.

Any thoughts??

probably a good guideline, but remember every car is set up differently, though I honestly haven't heard many good things about stiffening the rear sway on the Z. most people keep it OEM or the softest setting unless you want to make the car unpredictable and snap oversteer a lot

While you’re waiting for the work to be done try raising your front tire pressure. The PS4S’s have a little more rollover than other tires on turn in and respond well to slightly higher pressures. Plus it’s free and easy to try as a starting point. Also measure the ride height front/back to see if the front of the car is higher than the rear. Lower it if it is.

It's not a simple question or a simple answer. Assuming your doing all the right things with the brakes throttle and steering inputs (not an easy thing to do). Here's a nice little flow chart.
https://drivingfast.net/wp-content/u...osis-guide.png

While I agree that in a typical setup for an FR car that is seeing track duty this would make the car snap oversteer, the problem is the OP is saying that his car is massively understeering now and after reviewing everything he has and the things he's not willing to change, he is really backing himself into a corner. So either he stiffens the rear via the sway bar, full stiff is probably too aggressive so maybe soften the front sway bar to the softest setting instead and leave the rear in the middle or wherever it's currently at. Or he has to play with camber and toe, my guess is that if I'm running a square setup with -3.25 front camber and -2.4 rear he's going to need more negative camber than me to get close to the same feeling i'm getting. That brings in a whole new problem with tire wear due to the camber.

Thanks for having my back Bob, you da man :tup: In all seriousnes everything i've learned about suspension has been from my driving coach, my friends who have been doing time attack for years, the racers who have come before me on this forum and the past 12 months of tracking that have allowed me to test and tune and see what really works and doesn't.

@igota21incher The ball's in your court dude, there are different schools of thought on how to tune the car to your liking but it really comes down to you. Caution should be exercised whatever the case may be.

LOL, your results says it all. Yep, one ride with Steve and I learned a ton. I won't get some more time with him at course like Streets or Buttonwillow. Something more technical than Auto Club. He was the one that told me to get rid of rear bar. I need him to drive it and give some additional advice on my suspension. It is a little more complicated having a big arse wing, spiltter and canards.

Let me know the next event you are going to attend after this month and maybe I can go play too. :tiphat:

The one thing I have learned while on the forum is this. Go with a square setup. 285,305, or 315's. Go with the stiffest front bar you can. Hotchkis is the stiffest. Remove the rear bar. For spring rates start at 14k fronts and 11-12k rears. Progressive springs are not for the track. If you go with slicks these rates will be much greater. Front Camber start at -3 and for rear camber start at -2. First mods after some seat time are oil cooler, better brake fluid and pads, front brake cooling ducts, and a good LSD diff. So, you can pick and choose what you want to do with your current setup but it will still feel like ****.

Solid advice from all (esp the track guys)! I have scheduled some shop time next Saturday; will report back as soon as I’ve had a chance to take her on some winding roads.

Question. Will this car ever see the track? You said that you are getting understeer in the twisties. So it's street. Track set-up on the street will KILL tire life. Pick your poison. You screwed up on your front tire size.:shakes head: Should have went with a 275/35-19. And now you want a work around. Ain't going to happen. Get the SPL upper control arms. For the street. Front camber at -2.0, caster at +6 to +7, toe should be 1/16" in. Rear camber at -1.75, rear toe at 1/16" in. If you set the rear toe to zero, and out. You will get a condition called snap-oversteer. It doesn't happen all the time, but when is does. You will be cleaning out your shorts! :eek: It's scary when you are looking at the guy behind you, eyeball to eyeball. :eek: Front sway bar full stiff, rear bar full soft. The front of the Z has too much roll in it. You WILL have to change the dampening on your coilovers. If not. You are SCREWED! If you are not willing to make changes. You are doomed!

My set-up. I'm running bigger tires then most anyone.

Front 285/35-19 PS4S on 19x9.5, +25. Rear 345/30-19 PSS on 19x12, +28.
Front camber -2.5, caster +6.5, 1/16" toe in.
Rear camber -1.8, 1/16" toe in.
Hotchkis front sway bar, stock rear sway bar.
Rear diff is a OS Giken set-up at a 1.5 way, with 70% lock up.
My whole suspension is out of the SPL catalog. No rubber bushings.
I turn off my VDC and have done the YAW sensor mod too.
My Z likes to dart around. It's a bit nervous. :tup:

Go to the track so you can pinpoint exactly where the car is understeering.

You need more front camber in this car, there is too much weight up front to only have -1 camber.

If you can get the specs you want with SPC, you don't need to get SPL arms.

Show off!!!

This is a great place to start and works well for a dual purpose track and street car that sees some twisty road time. If you are just dd the car there is nothing wrong with having front camber at -1.0 to -1.5 to extend tire life and if you want to maximize straight line speed....well that's a whole other story.

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:D

What's 1/16" in degrees? Everything else I've read around the forum etc. notes Rear toe MUST be double the value of the front.

FWIW I'm running 255 fronts 325 rear aggressive street only, no track. All OE suspension other than front sway bar and rear adjustable camber/toe bars. ZERO understeer and the tires won't unevenly wear as bad.

Caster 5*
Front camber (not adjustable) -1.02*, -1.23*
Front toe 0.09*

Rear camber -1.04*
Rear toe .018*

Toe in inches is the old way. The way I was taught doing alignments many years ago. Also toe in inches is affected by size diameter. Where in degrees is off of vehicle center line. Tire diameter won't affect it.

So 1/16" toe in with a 27" tire is .1326288 deg total toe. Or .0663144 deg for one wheel.

For the rear toe. A lot of the track rats here run close to zero toe on the rear. Helps the car rotate.

255 front, 325 rear, and no understeer? You really haven't pushed all that hard. :driving:

How is that even possible? No understeer?

You just go straight and then make a granny turn to the left or right!

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Thanks for explaining the inches measurement, interesting substitute.

I guess understeer is subjective. Sure if I go 100 mph into a round about I'll get understeer but for the purposes of the OP, which are spirited street/twisties driving I do not have any.

Give me a legitimate scenario to test and I'll do so. As mentioned above, such a test won't be 100 mph into a round about as the most track savy Z on this forum will even understeer in such a circumstance.

You don't have to be traveling at a 100 mph to have understeer. Understeer is when you turn the wheel and the car continues to go straight and adding addition input or turning does not help in getting the car to turn. I NASCAR they call it push because car wants to push through the turn. So Rusty's comment that you aren't driving hard enough refers to how aggressively you take a turn and that can be at 15 mph. It is about your inputs, speed into the corner and power out of said corner. So with your tire combination and the weight of the front end of the Z it is going to understeer when driven hard or at the limit for your tire and alignment setup.

This.

My old Accord coupe (FF of course) would understeer like hell at 10 mph in the right scenario. It used to happen to me all the time.

But its more fun when you are.

https://youtu.be/Mmgk-LvZdfc