How can I improve 350z's handling?

I own a 2005 350z and it's somewhat modified. I bought it like that. It has Tanaba GF210 springs, 19" wheels that are staggered. Tires are 245/35/19 in front and 275/35/19 in the rears. That's it for the suspension mods.

I've never been to a track day but I did my first all-day autocross session and got over 40 runs in. And driving my Z everyday I have begun to realize its flaws. It has massive understeer!!

I'd like to hear from people who have owned or driven a Z to see if I am right about this, also would like advice.

I have owned two different 99-04 mustang GTs, an S2000, eclipse, BMW e46 3 series, toyota celica GTS. I may not be too familiar with suspension mods but I can compare between the cars I've owned. The s2000 handled like it was a go-cart, it was glued to the floor and it would just turn and turn and turn without end in sight. It had zero understeer and maybe a little bit of oversteer. but everything so light and nimble it was easily correctable.

The Z however has such low and loose responsiveness in the front end. What I mean by this is.. when you turn the steering wheel, it will take a split delay before the wheels turn in. I'm not just talking taking a corner or a turn, if you drive down the street and just move the steering wheel back and forth (left right left right) to simulate slaloms, it will feel delayed, loose and un-sharp. My 01 mustang GT was like this. It felt like I was steering a goddamn boat. I would turn and then it would turn in very slowly, delayed. The Z isn't as bad but it's noticeable. The S2000 was the opposite of this problem. The steering was SO sensitive that i felt if i fell asleep at the wheel for even a split second i could hit the wall. If you move the steering wheel an inch in either direction, the car will go that way. I would like to get this in my Z, and I don't know where to start in terms of mods.

I'm not looking to turn my Z into a track car as it is my daily driver but the understeer and dull steering is actually very annoying in every day driving. When on the highway or turning around corner, the Z feels heavy and doesn't feel like it wants to move. Like its fighting me every step of the way when turning. And i do plan on autocrossing and tracking a few times a year for fun. Don't even get me started on autocross, the Z had such bad understeer it was ridiculous.

Could the 19" rims be the cause of the problem (moreso than stock)? If i went with light 18" rims like the popular enkei RPF1s and upgraded the sway bars, would that fix the Z's steering responsive feeling? I want the front end to feel "lighter" and turn sharply without feeling like I am fighting it.

I'm not sure if any of this makes sense but if anyone has thoughts or previous 350z experience, i'd love to hear it.

What brand / model tire are on the car right now? What about the alignment / condition of the tie rods / ball joints. It sounds like your alignment is jacked up.

In reply to pimpm3:

I believe they are Kumho Ecsta SPTs, they're fairly new. I looked at the ball joints and they seem okay. The car is under 100k miles and daily driven. Not really on harsh roads and i've only been autocross once. What makes you say the alignment is off? I thought alignment has to do with the car driving straight? Dont get me wrong the car turns but it just has noticeable understeer.

https://www.youtube.com/watch?v=e2ZblaJ62_8 Here's 2 runs at the autocross session. You might be able to tell that I had to slow or tap the brakes a few times to get it to turn on wider turns.

didn't the now defunct Sport Compact Car do something with the Z where they put non-staggered wheels on it?

alignment can do a lot more than keep the car going straight. the amount of tow (toe?) can really affect the way the car turns in. you likely want the slightest bit of tow out for quick turn in (1/16"). What ever you decide to do, a good alignment is something you should add to your list. Don't do it first though if you're going to be changing out a lot of stuff.

You seem to have two seperate issues: slow turn-in followed by understeer.

The understeer is easy enough to fix. Go to square tires, i.e. same width tires and wheels front and rear. This is the setup used by most guys that track their 350z. A lot of them seem to run 285 front and rear. This will also allow you to rotate your tires and extend their life tremendously. You might want to run some decent track rubber as well. I'd start with one of the current 200tw street tires.

For the turn-in, the tires might help, but if you really have slow turn-in and numb steering, I'd look at the bushing (100k on original bushings is a lot), and then a good alignment with some toe out.

My first thought was a square tire setup as well. It probably won't solve the problem completely but I think it will correct the handling bias and make maintenance much easier and cheaper.

The all-season Kumhos are not likely helping either. I would look for a set of square 18" Track wheels (the lightweight six spokes) and mount some real performance rubber like BFG Rivals, Star Specs, ExtremeContact DWs, or what have you in a non-staggered sizing. You will also get some acceleration and braking back due to the ~40lb reduction in unsprung wheel mass.

A fat front sway bar will also help with the under steer. I'd definitely have it aligned, if it has lowering springs there is a fair chamce it wasn't aligned and the lower stiffer spring likely are too much for the stock shocks so you'll want to upgrade them as well.

Step 1: Square wheel and tire setup ASAP. Get better tires. 17x9 or 18x9 with 255s if you want to run STR
Step 2: Better alignment
Step 3: Bigger front bar, depending on what you do with springs

As a data point... on the AP2 S2000 I went from the stock setup (17x7 215 F, 17x8.5 245 R), which handled OK, to a square setup (17x9/245) with a CR (slightly bigger) front bar and it went to OMG INSTANT TURN AND ROTATE and also a little bit too loose (should've done a bigger front bar)

Could the delay in response of the Z vs the S2000 be due to body roll? A car that rolls alot will be slow in transience when compared to a car that is stiffer and better damped. Your springs are lower/stiffer, but how low is it? Are the lower control arms parallel to the ground, or canted? If canted, are they higher at the chassis side, or the lower ball joint? Cars that are too low (chassis side is lower than lower ball joint) will experience more roll at the same spring rate than a car that sits higher due to roll centers, and more roll will feel slower to respond.

My take: Check the alignment (zero toe, or slight toe out in the front, toe in rear?), ride height, throw some good shocks on (Tokico Illumina or Koni yellows) at it and try again.

My brother had the G35 when I had my 99 mustang gt. If your car handles more like the mustang than the s2000, you are missing out on a world of fun. Square the tires/wheels, check all suspension pieces over very carefully and replace anything that appears used. I am sure this alone will make your car turn exceptionally well.

These are hard on bushings...I would change them anyway if they are original. You're carrying more weight than the S2000, so you have to account for the transfer. Like everyone else said, tires, shocks, bushings, wheels, alignment. Also, the way you drive could be different. Not all cars react the same and take different styles. You may be carrying too much speed on corner entry.

evildky wrote: A fat front sway bar will also help with the under steer. I'd definitely have it aligned, if it has lowering springs there is a fair chamce it wasn't aligned and the lower stiffer spring likely are too much for the stock shocks so you'll want to upgrade them as well.

A larger front anti-roll bar will make it understeer more, not less. And you also need to put some negative camber in the front suspension, like 1-2 degrees.

well for one 255s all around were better for me than my staggered setup when i owned one of these. The consensus seemed to be that was the best handling setup at the time which is why i switched it it and it was

jstein77 wrote:

evildky wrote: A fat front sway bar will also help with the under steer. I'd definitely have it aligned, if it has lowering springs there is a fair chamce it wasn't aligned and the lower stiffer spring likely are too much for the stock shocks so you'll want to upgrade them as well.

A larger front anti-roll bar will make it understeer more, not less.

This is not a hard rule, at all. See numerous threads on the subject.

Also note that 99% of RWD stock-class autox cars run a larger front swaybar to mitigate understeer.

A larger front bar will decrease understeer if the tires are rolling onto their sidewalls due to excessive body roll. I don't believe this is the case with the Z, even a stock one.

Check your lower control arms, lower ball joints, and tension rods...Z's and G's eat these things like crazy (especially LCA's).

jstein77 wrote: A larger front bar will decrease understeer if the tires are rolling onto their sidewalls due to excessive body roll. I don't believe this is the case with the Z, even a stock one.

Well, most prepped stock-class 350Zs are running a bigger front bar.

jstein77 wrote: A larger front bar will decrease understeer if the tires are rolling onto their sidewalls due to excessive body roll. I don't believe this is the case with the Z, even a stock one.

Finally, the correct answer.

The generalization that increasing front roll stiffness tends to increase understeer is valid, but on some cars that do roll the tires, reducing the contact patch and allowing the front tires to slide, increasing front roll stiffness a bit tends to stop the roll and have the opposite effect. Just don't go too far and consider balancing the increased front bar with a slightly stiffer rear bar. My MGC is a good example of a car that needed more front stiffness to counteract understeer.

How do you improve the handling of a 350z? Sell it and buy an e36 M3.

A fatter than stock front bar will keep the car flatter on the turns moving some of the weight to your inside tire as well as your rear tires. It's a bit counterintuitive but valid none the less.

You also can't really compare the handling of a 350z to an s2k. While I have not yet driven an s2k my understanding is that their steering is nearly telepathic. And the national results clearly indicate they are light years apart.

Yes the E36 is a great handling car, but for the added cost of maintenance and repairs on the bmw you could have 2 350's

How many miles are on it? You said under "100k miles". Does that mean 20k or 90k?

To me, it sounds like you may be experiencing some wear issues.

Shocks If mileage is closer to 100k and you are on stock shocks (especially w/ stiffer aftermarket springs), they are probably in desperate need of replacement. A worn out shock will not properly control the tire. If that shock is on the front end, that will feel like understeer. You'll also get more body roll and brake dive b /c the shocks can't control body movements cuz it's worn out.

Bushings Again, at close to 100k miles your suspension bushings may be worn causing deflection in suspension components under load resulting in a looser feel and inaccuracies in steering input.

Ball joints and tie rod ends might have some wear at this point as well. Might not be bad enough to cause your issues but worth investigating

Focus on these wear items before throwing more, expensive parts at the problem. Especially wheels and tires. Square tire setup is nice but you can usually use sway bars to adjust roll stiffness and the resulting under or over steer. Wide tires up front can also result in your car tramlining more in regular street driving which is annoying.

evildky wrote: And the national results clearly indicate they are light years apart.

Were you talking about STR, which was won by a physics-challenged 350Z this year?

http://scca.cdn.racersites.com/prod/assets/results/2013%20Tire%20Rack%20Solo%20Nationals.pdf

Linky fail, I was thinking stock class, CS car vs BS car (previously BS and AS cars FWIW)

Once you start prepping cars it all goes out the window, and we all know that all drivers are not created equal. Sometimes the right driver in the "wrong" car does win. But the sea of BS s2k's are faster than the few CS Z33's (If I could find the actual results that would be helpful)