Front/rear sway bar questions

geokots

This is sort of a sway bar 101 type question. Yes I looked but couldn't find something specific to this.

Now that my car is about to got to sleep for the winter, I'm starting to plan what I'm going to do in the spring. I am most likely going with Eibach Pro springs for a slight drop and stiffness. No, not going with Coilovers as it's a little overkill for my needs. I'm familiar with the Eibach Pro kit from having them on my Mustang Ecoboost.

I'm thinking of also getting the swaybars from Eibach. I've read (but can't find the post) that the Z benefits from upgrading the front but not the back. Is this true? Also what are the pros and cons of upgrading the sway bars? I see that there are 3 ways to mount them, again pros and cons.

Sorry if this has already been answered 100 times. When a car has been around as long as this, sometimes things get lost in the noise.

chowtoo

I would also like to hear the answers to these questions. I have seen a lot of comments on the subject but it would be nice to see them all summarized to pros and cons.
Thanks!

JARblue

A stiff front sway bar will reduce understeer and help you turn in better. A stiff rear bar will induce more oversteer, so track people tend to prefer softer sway bar in the rear. That's why you see a lot of people put on a Hotchkis front bar because it is the stiffest one on the market and then go with either the soft OEM rear bar or no rear bar to reduce oversteer.

__________________

cv129

Just a caution for the green horns (myself included)....This is true in case of Z34 (although I’m unsure it’s actually used to further assist the rear or directly affect the front, don’t know the math), but in general the opposite is true.

__________________
Setrab | RE-71 | SPL | JRZ | Nismo | ARK | Whiteline | RacingBrake | CJM Oil Pan | Ti shield

JARblue

There's plenty of info out there and it's not hard to find. These were the first two threads that came up when I searched:

Is the front sway bar what i want? Noob question

Question on sway bar set up

__________________

OptionZero

for bumming around on the street, completely and utterly unnecessary and a waste of money

for track, you want Hotchkis. Whether front and rear or just front depends on your driving style and rest of the setup

but for you . . . save the money

__________________
OptionZero Build Thread

JARblue

Good point. It should be noted that the Z chassis has a lot of roll for a sports car so a stiff front sway bar helps reduce understeer because the car is not lacking for grip. With a heavier vehicle and less grip from the tires, a stiff front sway bar can cause a lot more push through the turns (i.e. increase understeer).

__________________

gomer_110

Skip the Eibach bar and just go with the Hotchkis front bar. The only reason to you need to mess with the rear bar is if you don't know how to rotate the car with the throttle.

__________________
'11 370Z Nismo #528 Fast Intentions | Stillen | Motordyne | Uprev | CSF | Zspeed | Z1 Motorsports | AST | Swift | SPC | SPL | Whiteline | Hotchkis | Bride | Schroth | Robispec | Cusco | Nismo | Volk | Forgestar | Hoosier | RJM
'17 Titan Bone Stock

markesc

yeah the hotchkis front bar TRANSFORMED my 370z.

DO IT!!!!

I kept the stock rear swaybar, which for daily use, helps keep the rear from losing traction over non compliant surfaces. Being that all of our roads in this country are garbage, I'd recommend keeping it stock.

The front swaybar to this day was the best $$$ spent on the Z.

Ralphatron

I was just about to post a new thread about this until that second to last sentence caught my eye...

I'm clearly a noob and wanted a very aggressive handling car so I threw a bunch of money at coilovers and both front AND back hotchkis sway bars for my 6 month old '20 sport . Now I wish I was kidding you when I say this, but I've already been through 3 separate coilover kits because I've been on a mission to find the right balance of street drivability and performance. First was the digressive series kit from BC, then the true rear BR series, and finally the divorced spring BR series.

Right now I have the divorced spring style kit, and BOTH hotchkis bars on my car. I'm about to give up and go back to just stock struts and lowering springs because the instability in the car when going over medium bumps is driving me insane, but I'm starting to truly suspect its the sway bars, or at least the rear sway bar (which I have the links going through the middle hole of the 3).

Aside from oversteer/understeer issues with a rear sway, I'm hoping someone can tell me that Im an idiot for not expecting this. I know the sways can act as additional spring stiffness when only one side hits an imperfection, but can it really make the car feel that much stiffer/unstable over bumps? I've got the dampers all set to the softest setting too, and default spring rates as well.

Sorry for the story book post, I'm just trying to figure this out.

Jhill

Really easy way to find out, disconnect one side of the bar and drive it. I’ve ran some stiff bars on another car and then moved to softer and could say the ride was better over uneven terrain but I don’t know if I’d go as far as saying unstable. Then again the hotchkis is a pretty massive bar. If spec on the net are correct I think the eibachs would be a interesting set to use since between the adjustment ranges it’s the only set I’ve seen that can go either way as a stiffer front bar vs rear (in ratio) or a stiffer rear vs front (in ratio). So theoretically they should have the widest range of tune ability.. I was pretty surprised to see the stillen even at the stiffest front setting only being marginally stiffer than the softest rear.

Brendan

There are a lot of variables there to consider. What are the spring rates you went with? What are the alignment settings? What is the ride height? How much down travel do you have? How are the dampers set up? Etc...

I ran into some really weird handling issues with my car when I went to higher rate springs. The car would dart around on bumps so badly that a passenger could feel it. My issue came down to not enough down travel meaning that one or more wheels was constantly struggling to make contact with the ground. What helped me was adding a set of helper springs to the car. This gave me way more down travel and made the car handle bumps a lot better.

I also don't run a rear bar because I found it much easier to get the power down without one. I just increased my spring rates to get the right balance or rotation for my needs.

Here is a link to my short write up from by build thread:
Rear helper springs

Spooler

Responded to your thread, I need to do this on my car.

Ralphatron

yeah, I think what I'm going to do first is move the end link to the outer hole (softest setting) on the rear sway. You're saying just unlink one side and basically leave the endlink hanging there to test this out? any potential issues I can run into while driving it this way for a bit?

Yeah, the adventure I've been on the past few months trying to get this right has taught me about all the factors that come into play with suspension.

the second coilover kit I put on had custom swift springs at 12k in the front and 7k in the rear (true rear, not divorced spring). This was BRUTAL to drive and I immediately threw on 10k/5k swifts and noticed a huge difference. But I assumed the custom valved dampers for the 12k/7k original springs on this kit were causing it to still be too stiff for daily street driving.

That's why I went with a completely new divorced spring kit, using default spring rates of 10k front and 8k rear. As I'm sure you know, the spring rate is basically double for divorced spring vs true rear coilover spring due to the wheel rate.

This was also noticeably better, but I'm still feeling what I think you described as "darting" (car slightly being thrown left or right I think?) when hitting bumps with one side of the car only.

The other thing too is that I have yet to get my alignment done, because I wanted to finalize my configuration before spending the 100 bucks and avoid having to do it again if I wanted to change something. I know this will affect handling, but I didn't think it would be enough to cause my issue, right?

As for ride height, I'm not slammed, and I'm not at stock height. I'd say right now I'm noticing this at maybe 1.5 inches lower than stock, so nothing extreme but was planning to fine tune the height adjustment to maybe a half inch lower than it is now, just waiting for springs to settle a bit first.

I'm not really sure what down travel is. I'm on the default dampers that come with the BR series coilovers from BC and I have them set to the softest of the 30 available settings.

I appreciate the responses, guys, thank you!

Jhill

The hotchkiss definitely see to be a fan favorite here but I’d also consider what tires your going to use. If the bar is too stiff you can overpower the tires, so when choosing you have to look at it as a package. I went with the stillen because of the adjustability at the time and also know I’m not running R compounds or slicks but choosing now eibachs do look like a nice in between and would be tempting.