JMII

So I've been tracking my 2003 Touring for 4 years now and slowly improving my times and enjoying things. Several months ago I added a Hotchkis sway bar set at hole 3 front (82% stiffer) and hole 1 rear (80% stiffer) and while turn in seems better the car still leans like tall ship in heavy seas... see attached pictures.





Is this expected on stock suspension? I honestly thought the sway bar would level things out more. Car has 71K miles and suspension seems fine, it doesn't squeak or rattle. Should I just go stiffer on the front bar or do I need to start looking into springs/dampers or coilovers?

I have not modified the suspension yet because the car rides so stiffly already. It crashes over bumps and jolts you around plenty as is. Things got a little worst when I added the Akebono brakes and bigger tires (245/40-18 front - 265/40-18 rear Hankook RS3 on V2 Touring Wheels) I assume due to the larger unsprung mass. However rough riding seems to be a standard '03 Z handling trait and I certain don't want it to become any worst since the car is also my Daily Driver.

dkmura

iTrader: (64)

Ride isn't affected by swaybar settings, unless you're driving up steep, jagged mountains. There's not a lot of ride height built into the Z33 and I notice how many potholes and expansion joints simply jolt my Z onto the bump stops. The Z33 racecar is quite a bit stiffer, and I'm currently converting it over to full Koni 2812s DA shocks, so body roll isn't the biggest issue. I'd suggest at least trying the front bar on full stiff, if you haven't already.

MicVelo

Couple of things on this JM... if you're on stock '03 suspension, bear in mind that Nissan screwed the pooch (excuse me for that... only way to describe) on the '03-04.5 shock/spring combination. Very "jolty" and not at all a balanced nor smooth ride. That was corrected in '04.5 models forward as they either softened the shocks or altered the spring rate (can't remember exactly which).

This is especially exacerbated when the miles pile on and/or the car is subjected to "use at the limits", e.g. track use.

In any event, it's likely that a good set of springs/shocks will greatly improve/reduce rollover.

But try this first... your sway bar settings, technically speaking, with a front-to-rear sway bar delta like you have it - front relatively stiff, position wise, and a softer rear - should yield a greater amount of understeer and that, in turn, will cause the car to lean more because you are having to crank in more front steer for a given corner and consequently, shifts more weight to the outside. At least that's the theory... it all depends on the track and the camber (or off camber) of the turns. In an off-camber-turn (or flat) situation, this is certainly true.

This isn't gospel but I would dial in a little more angle on the rear bar (adding roll stiffness in back) and lean the car more towards neutral and/or oversteer. One hole adjustment should do the trick. And, if you want to really get creative - without corner weighting - you can adjust the rear bar to different holes/angles to suit a particular track - depending on the ratio of left vs right turns, majority rules. But I'd start with a unilateral adjustment to both sides being equal first.

Put this way, adjustability is at your fingertips so why not give it a try before your next track event? Do some testing before you get on track or during practice of course. Track side adjustment should be a relatively easy thing to do.

Good luck!

guitman32

iTrader: (15)

You definitely need stiffer springs and matching dampers to control the roll. You will be surprised how stiff you can go and still get substantial body roll. That is a function of how this chassis and suspension are designed, and why teams like the Doran Racing CTSCC 370z pursued custom ultra stiff front sways, which are necessary to further the front roll resistance once you reach the ideal spring rates for a given track.

Keep in mind our chassis has the benefit of great tire wear, mechanical grip and braking performance, so dont think the above is entirely a negative.

JMII

Thanks - this is pretty much what I thought. I was going to stiffen the front bar as that is where the problem appears to be, but I understand what you are saying: I need to tweak the rear because I'm actually fighting the car's tendency to understeer.

This was my worry: putting really stiff springs on the car (I don't want to lower it) and then knocking all my fillings loose only to find the overall problem remains, IE: the car is leaning by design. In some ways it makes sense to get the weight over the tires you are asking to do the most work. I assume too stiff will start lifting the inside wheel causing lack of grip, especially in the rear.

Overall do these adjustable coilovers like Ohlins DFV Road & Track really provide a smooth ride when set to soft but then can be stiffened up for track work? Since I daily the car I don't want full on race car stiff all day every day. Given the '03's jolty stock ride I assume most aftermarket dampers would be an improvement. Since my mileage is getting up there a suspension upgrade soon is sort of expected.

guitman32

iTrader: (15)

Even with stiff springs a well valved suspension is still surprisingly compliant on our platform. I would say an off the shelf DFV kit is probably the perfect fit for you for the money.

03threefiftyz

iTrader: (25)

It's a give and take. My car has big spring rates, custom penske's, etc etc...but it still moves around a fair amount.

CK_32

iTrader: (1)

Get some quality clips.

You're chasing your tail messing with the sways for what coils are made for.

terrasmak

iTrader: (8)

Also have high rates, and you can still see a bit of roll

MicVelo

While you'll never rid the car of body roll *entirely*, just be glad there's a fairly small amount to try to mitigate. Unlike...



Physics and all.

13esim

I'll follow up MicVelo's by one of my friends' Civic at autocross:




But on our cars, I have a set of Tein coilovers, nothing crazy (12kg front springs and 10 kg rear springs) and still get a considerable amount of body roll.

JMII

After seeing that BMW and Civic I feel much better I didn't expect my Z to be FLAT with just sways... just wondering what level of roll should be expected on stock springs/dampers and how I might reduce it.



I'm getting smoother in my transitions which is removing some of the tipsy action. For example the 13/14/15 turn complex at Homestead (my home track) I no longer feel like my helmet is going to hit my shoulders.

The picture I posted above with the rescue truck in the shot is turn 3 (@ approx 35 MPH) I believe. While the one with Porsche is from turn 6 (@ approx 55 MPH) for sure. In both turns Harry's lap timer running on my iPhone claims 0.8 g max, but I know that it not a professional level calibrated tool.