OK, I am looking for a final answer to this. I have gone back and forth, and really I am still unsure. I have heard that the springs are there just for support, and the only aftermarket springs you can get will just lower the car. Well, I really don't want to lower the car, just looking to increase my cornering ability and decrease body roll.

Now of course, like the name suggests, anti-roll bars lessen roll. Now this is a good thing, but I was told a while back that this really doesn't increase cornering ability. It puts more pressure on the outside tire during cornering in order to make the car flatter in the corner. But, it takes even more pressure off the inside tire, which decreases its effectiveness even more. Now, I don't know if sway bars will increase the Gs of the car or not, but it will make the car feel better in the turns.

None of the springs offered have spring rates that are much higher than stock, and they all want to lower the car. Are sway bars the only thing that can semi-solve the problem that I am wanting to solve?? I don't want to spend an arm and a leg on a coilover kit, and someone told me that they are mainly good if you want to lower your car or change the damping. I just want more Gs, what is the best way to do that?!?!?!

 

For more Lateral G's you need all of the above including sticky Tires..theres no way around it ...just springs will help because they actually lower the cars center of gravity...but good coilovers are a good starting point.

 

I'm new to racing, but as an engineer I can attempt to answer this from a physics standpoint.

First, the short answer - Both will work to help improve handling. Sways are probably the quickest route to improving the balance in steady state corners. Springs, especially those that lower primarily the front, will help add some needed negative camber to improve the contact patch during hard cornering. Springs may also improve the dynamic response during transient cornering (like slaloms) where you are rapidly transitioning from one direction to another.

Now, the long answer - In a steady state corner, the weight distribution on the tires is determined only by the location of the CG (center of gravity) and the lateral acceleration (OK, this would be a very simple generalization, but should be sufficent to get the idea across). The simplest way to view this is by visualizing the "car system" as two components - the unsprung weight is one component, and the sprung weight is another. When you corner, all the springs, shocks, sways, etc. are working within the "car system", and the only external forces are those generated by the tires and by the acceleration of the entire mass (which acts at the CG). When you look at the vehicle in this manner, you see that the springs, shocks, and sways can all be reduced to how they control the location of the CD. So, for randcom cornering grip is equalized best when the CG is as low and centered as possible (unless you turn only in one direction, in which case you want the CG as close to the inside wheels as possible). The springs, shock, and sways all become much more complex during the transient stage of cornering, because they will all determine how the loads on the tires ramp up before the steady state is reached and when bumps are encountered in the middle of a turn. For steady state cornering though, the knowing how the CG will be affected will give you a good idea of what is happening.

Also this also helps show that your description of the workings of the anti-roll bar is incorrect. The anti-roll bar does not increase the pressure on the outside wheel - in fact, it does the opposite. As the outside suspension compresses, the anti-roll bar transfers some of that compression to the suspension of the inside wheel. This causes the entire car to basically "squat" as it corners, which lowers the CG and keeps it more centered, distributing the weight better between the inside and outside wheels. From an external perspective, the weight distribution is better balanced with a stiff anti-roll bar than with a flexible one.

Stiffer springs will also reduce roll, because there is less compression on the outside and extension in the inside before the forces are balanced. Stiffer springs will also increase the natural frequency of the car, which could help in trasient cornering like slaloms. Shorter springs will lower the car and can increase the negative camber of the suspension. This can be both good and bad depending on how you use your car.

So, applying this to the Z, here's what I see:

Problems - Little front Camber and some understeer:
Since the Z has very little front camber, we are able to bring the tire on edge during cornering and loose some of our contact patch. One way to solve this is to increase the front anti-roll bar stiffness to keep the car flatter, but this has the disadvantage of allowing the front to be less compliant which can cause it to break loose. Therefore, this solution would work best if you also increase the stiffness of the rear bar to bring the car back into balance. That is why most anti-sway bar kits offer both front and rear upgrades.
Another solution is to lower the front of the car which helps add negative camber. This is probably a good solution unless you are concerned about inside tire wear, and is probably why so many of the spring kits also lower the car a bit. You want to be careful about lowering the rear, though, because that would increase the negative camber in the rear, which could potentially cause excessive grip and bring you back to the understeer problem.

So, if you are primarily interested in reducing the understeer, then a set of sways is probably the most cost effective route.

If you also want to increase the overall grip (by lowering the front and maybe the rear) and make things a bit stiffer, then changing the springs will help with that.

-D'oh!

PS- Feel free to correct, add or clarify, anything I've said. I believe I am correct on this, but It's definitely possible that I've forgotten something important.

-D!

 

Get coilovers from a brand you believe in that have spring rates that max out the extra mount of stiffness you see yourself as tollerating. Anti roll bars will lesson roll, but should really be used to tune the chassis behavior to suit your total setup, your driving enviroment and style.

I would recommend Jic FLT-A2's and EVO350 swaybars (the EVO bars are 3 way adjustable front and rear).

At one time, the owner of progress group said he'd be willing to check into making me a set of custom springs for a different car. But that was 2 years ago. Just a thought. BTW, he's a super guy to talk to. (Last time I checked he doesn't offer any Z stuff right now).

 

yea I checked with progress group and nothing on the horizon for the Z yet..unbelievable considering how popular the Z is and how well it has sold..

 

Interesting, two different responses already.

From what has been told to me, it is hard to compare spring rates for different coilover kits cause the struts and everything change, so you are not really comparing apples to apples. It has been also said that the replacement of springs is mainly to adjust ride height, which I don't want to do.

I am thinking about the 350EVO bars, cause of their adjustability. There are really no springs out there that meet what I want. As for coilover kits, I don't want to spend that kind of money, plus I am satisfied with the stock ride minus the bounce. Maybe some Konis would be the answer for that, but that is beyond this trend. I run 19" toyos, so my handling feels better than stock, but I just want more!!!!!! I want the cheapest answer, springs or sways or what??

BTW, Gcoupe35, you have a PM.

 

Spring rates do matter, I wouldn't have gone to extraordinary efforts to find out the stock spring rates if they didn't. I needed a base line for comparison.

Any coilover maker that's worth spending a dime on, that runs a spring stiffer than stock will valve the dampeners stiffer to control the stiffer spring correctly, stiffer valving means a stiffer ride. If you have selected coilovers that have adjustable dampeners, you can dail out a certain amount of that to gain some ride quality back but,............the cost is a lower spring control factor for that given spring rate and all the things that come along with that, including lessoned performance.

 

I understand what you are saying, but again, I am trying to find the thing that can improve the aspects I want the most for the least amount of money. I don't want any ride height adjustment, and I want to keep drivability of my daily driver. I don't think you have to spend $1500-$2000 to do this.

BTW, I am not discounting coilover kits, just want a little more cornering ability without feeling like I am riding on a skateboard.

In other words, what gives you the most bang for the buck??

 

Just throw on a set of the 350EVO Swaybars and you will be amazed at the improvement in cornering speeds and stability. If you want more, then look at springs/shocks. The best part is the bars are adjustable so you can re-balance the car with different settings after you install new springs/shocks. Why would anyone buy Nismo or any other bar that is not adjustable!

 

Tires.

Upgrading your tires will give you better cornering grip than any other mod. Try some R-compounds, like Toyo RA-1's. Even Falken Azenis Sports are a huge improvement over regular street tires (don't know if they're available in your size).

That said, I don't really know why you want to increase your cornering G's only. Why does that matter on the street? On the track you'll want to dial out the understeer, so you'll want more negative camber up front, stiffer sways (esp. rear), and R-compounds. Once you do all that, your cornering G's will naturally rise. You can't really expect big changes in your suspension from just changing a single component: they all work together in harmony. But if you want to change only one thing, make it your tires.

Emre

 

Yeah, tires are an option, although they really don't firm up the travel by the suspension and the feel of it. Just bought some tires though, need to wear them out first.

 

How much are the EVO sway bars and where can you get them? TIA

 

As others have said, the biggest single gain in G-forces will be supplied by upgrading tires, but you've already committed to a tire change... Furthermore, although better tires are a good thing, G-forces and good handling are not synonymous. The Z apparently needs increased front camber and increased rear roll-rate, to optimize it's handling: shorter springs will afford some opportunity for the first; swaybars the second.

The advantage with adjustable bars, is that you can tune them -- along with some toe adjustments -- to 'dial-in' the handling, which is good experience. However, springs are a fundamental part of the car's dynamics for the reasons already stated, and they are less expensive, if you can install them yourself. (BTW, the RSR springs are stock rate and will result in about half-degree camber increase.)

I started with a swaybar change, and am using the adjustable Stillen bars. With the front set at full soft (7% stiffer than stock) and the rear at full hard (70% stiffer), and on my stock OEM tires, there is still too much turn-in understeer... I suspect that the stock tires are simply inadequate for my desires, but getting more front camber is now a high priority.

Don't agonize over this too much, because you will ultimately want to do both. Have fun.

 

Yeah, the more I think about it, I really want something that doesn't punish my daily driver and my backside. The 350EVO might be the first thing on my list, and I am interested in the Tein basics, but would like to know more about them as in someones' thoughts on them and such. I really think the Tein basics and the Nismo S-tune would be quite similar, not based on anything, just a theory.