A few questions here regarding my handling characteristics with nismo sway bars and nismo suspension. My main concern is with the sways. Car has great steering response and much reduced body roll like everyone knows who put sway bars on. My concern is the handing on the highway going 90+ into sweeping smooth turns. The car feels edgy like the response in the steering is to quick like the car gets ahead of itself and have to be careful with how fast you turn the wheel I get the sensation the back end will come out. Its kind of hard to explain. Kind of like the suspension is not doing its works cause the sways are to stiff. Could that be the case? I have pilot sport 225/50/17 tires. Could it be that I do not have wide enough tires. I dont have any handling problems on off ramps with sharper turns. I would assume that theres no problem there because the car is shifting its weight more aggressivly. Also does anyone have any idea as to how much stiffer the nismo bars are than the stock ones or make a close guess based on the diameter of the bars.

 

Nismo bars are made to be a balance of more sport than stock but not too race style.
So they are not way to stiff. I think you need to adjust your driving style and i think 225 on the rears are too small of tires for our cars. I think if you get wider rears your problem will go away.

 

Hmmm, profile say's you have a sedan. Your running the Nismo S-tune suspension on the sedan (shocks/springs)? If you are, was it purchased from a dealer in the states or from a place like japanparts.com? Reason I ask is because japanparts.com has a sedan specific Nismo S-tune that is totally different than the S-tune suspension that is sold in the states for the coupe and Z. I have several idea's, but I want to pin down what your running for suspension besides the sways.

"All that's necessary for the forces of evil to win in the world is for enough good men to do nothing.”
Edmund Burke

G35 6mt

 

Gsedan35,

I am running the sedan nismo suspension I bought from japan parts springs and shocks. oz wheels 17x7 +45 and michelin pilot sport a/s 225/50/17. I got the sways after I purchased the suspension so I did get to drive the car with the stock sways and new suspension.. Then decided to get the sways and chose the nismo because I thought they would be the right balance. I did not want something overly stiff. I am not necesarily saying they are but from what I have read on here there not as stiff as the others out there. Do you have any idea what % wise in stiffness over the stocks bars?

 

I'm alway's trolling for stat's and specs on anything relating to the suspension's on the car's platform. In all the time I've been doing that, never once has Nismo sway bar stiffness spec's come my way. All we have to go by are the outer thicknesses of the bar's 36mm front and 22mm rear. But I also scan user review of suspension products and most Nismo bar owners do make comment's about how their car's have less understeer then before. One can go too stiff with sway bars, so stiff that they start to make the car's independent suspension act like it's not independent, that become a worse thing when the road surfaces become less then billard table smooth. But I don't see the Nismo's offering up that kind of stiffness. However, if the Nismo bars were adjustable, you would have been able to get under the car and changes the setting to dial in the cars behavior. But I doubt they are the reason for your car's behavior problem.

I'll bet the springs on the S-tune's are progressive and that may be the reason for what your feeling. If you have pics of the springs before they went on the car from your kit, can you please post them? If not, on the car will do.

Curious, how much did you end up paying for the S-tune suspension?

"All that's necessary for the forces of evil to win in the world is for enough good men to do nothing.”
Edmund Burke

G35 6mt

 

Well, I did have the suspension on the car for about a month before getting the sways and everything was fine but decided to get the sway bars to reduce body roll a bit and thats why I chose the nismo. I wish I would have got adjustable ones. On the minamal setting I think its either eibach or stillen its a 7% increse in stiffness over stock. I would think the nismos are more but if not there is no point in me getting adjustable but I would guess the nismos are more than that. I paid about $1100.00 with shipping from japan. Here is the link from japanparts with the photo of my exact suspension
http://www.japanparts.com/Pic/pic087/152-1.JPG as you can see mine have 7 coils on the springs/rear spring and the coupe and 350z nismo have five coils if you go on there site and look. Not sure what to do either sell my nismo sways and maybe buy stillen or eibachs or look for someone who is willing to trade. Isn't there a mathimatical way to calculate how stiff a sway bar is? there oviously has to be if other companies know what the increses are over stock. I think I even so a web site for it once. Don't get me wrong I am not saying the sways are totally ruining my handling or anything but something does not feel quite right from my description of the cars handling from my first post.

 

Yes you can use math to figure out stiffness of a metal bar. But, the problem is their is no way to do the calculation since it's next to impossible to know the distance of the bars lever arms and we do not know the wall thickness of hallow bars.

I'm most inclinded to say the behavior your experience is caused by the progressive springs.

Their is more to progressive springs regarding the compromise on performance for ride quality. The soft initial compression of the springs allow the car to roll more on turn in, then the momentum built up by this roll hits the firmer part of the spring. This puts a heavier load on the outside than linear springs because the linear springs would not have allowed as much roll in the first place. And most progressive springs don't have "seamless" transitions in rate. They change rate in significant steps as active coils bottom on each other. A sudden change in spring rate, while at the traction limit, can result in a nasty slide or can be felt as a unsettling behavior were the car doesn't feel settled or it feels as if it's nervous. And further still, a progressive spring has two or more rates on one spring, that's what makes them progressive. ...let's assume that for the first 2 inches or three coils, the rates are 250lbs per inch and that for the next two inches, the rate is 350 lbs per inch. Therefore, when at rest, suspension will be compressed on the 250lbs spring section, and the next inch of movement will be in the 350 lb per inch range.

Now let's use the same scenario......a corner is entered and the outside spring is compressed one inch and the inside spring is extended .75 inch...rememeber the rates!

Now you encounter a bump in the corner...and since you are currently using the outside spring at a rate of 350 lbs per inch and the inside spring rate of 250 lb per inch... and the suspension is compressed the additional two inches....what happens to the spring rates? Since they differ, the chassis rotates around the roll axis... and the vehicle attitude changes/rotates differently than when in steady state cornering! Its motion becomes slightly skewed since to offset the bump deflection each spring must work through a different spring rate! If you were to then hit another bump, the attitude would change again...and so forth. All of these things of course would not happen with linear springs.



"All that's necessary for the forces of evil to win in the world is for enough good men to do nothing.”
Edmund Burke

G35 6mt