Eibach Sway Bar Settings

tonythetiger

iv been dealing with oversteer for yrs, time to take out rear bar and just leave fronts at stiff settting.

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Halfkiddio

The easiest way to solve that issue is to basically order the entire SPL catalog. Solid bushings and all.

lightw8 370z

Sorry, new on the site. Whats is Spl?

will be buying a Z in spring and want to do suspension snd bushings first.

im assuming spl is aftermarket bushing but woukd live to get a link for it.

Memphis370Z

Nissan - 09+ 370Z (Z34) - SPLParts

Bshields22

I always thought the stiffer the front the more likely it is to understeer. What about sways with coils. Wouldn’t your coil setting come into play with the stiffness of the sways?

Would really like to know why the stiffest setting is best. Again, I always thought the stiffer the rear is compared the the front, the more oversteer you can produce.

What would be a good canyon/track set up with KWv3 and eibach sways? I know personal preference is a big factor but I’d like a recommend starting point based on people experience with sways and coils in general.

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gomer_110

Stiff front/soft rear yields better power down on corner exit since the rear of the car isn't immediately trying to come around with the slightest bit of throttle application.

Spring rates absolutely can be a factor. The question is how far down the rabbit hole do you want to go. The KWv3's definitely aren't unique enough to warrant anything beyond the stiff front and soft rear bar recommendation.

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'17 Titan Bone Stock

MaysEffect

You are right to think that, essentially the open variable is tire grip, if you don't have tires that have enough grip, having a large front ASB will overload the outside tires and cause the car to start to slide....overheat..slide some more. Additionally, having rear tires that simply have MORE grip than the front will also lead to a similar problem. With a oem type staggered setup, the care tends to naturally want to understeer a bit more for the later reason, thus some people choosing a larger rear bar.

Spring rates is often the contributing factor, as you can overcome similar issues of roll/dive/squat by using stiffer rates rather than using a swaybar, but this does not give you the added benefit of cross weighting. It's all a balancing act between these factors. Tires being a major proponent in choosing the correct balance.

Making the front stiffer is to do the exact opposite to the problem above. If a car naturally oversteers, it's most likely because the front tires have more grip than the rear (or the rear not having enough). This can happen by running a squared setup, a mixed tire setup (softer tires on the front) or a weight balancing problem...A very distant but equally important problem would be tire pressure and heat issues. Because our cars are weight biased slightly to the front, the rear will tend to slide out early in the turn causing a quick sensation of oversteer. Adding a larger front bar can balance this out for several reasons, ultimately it's done by increasing understeer slightly and cross weighting which allows the rear to sit (squat) into the corner. This is what Gomer described. IF the car still tends to understeer too much, then you probably do not have enough front grip or the spring rate is not optimized for the sway bars & corner loads.

This is a question of tires and alignment. IF you already have these parts installed and you are not getting what you want out of them, you may want to look into alignment settings and getting better tires if you don't already have something good.

Are you having a problem with turning accuracy? Mid corner grip?, bump stability?

A larger/stiffer front bar should help tame steering speed and thus oversteer moments. Conversely a larger rear bar can help turn in speed and agility all things being equal. You can tune your alignment and tire setup to make either work. Overall a larger/stiffer rear bar is less stable, certainly without significantly higher levels of downforce and tire grip.

Bshields22

Wow! both of you guys gave some great information

Thank you! Let me look into a few more things and if I have any more questions I'll def post again on this thread

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Natrix

I know I am reviving this thread from the dead, but felt the need to share a few thoughts after reading through all the posts...

Key Points

• For the street, my impression is that the stiffer front Eibach setting is too high. When going over single-wheel bumps, it pulls the car to either side and makes the ride on uneven surfaces a bit rough. Note that I am running 275s all around with the same wheel offset, so this exaggerates the effect. My rear Eibach bar is set to full soft. I have yet to try these settings on the track.
• I tried running no rear bar on the track with the square setup and do not recommend it. It might be because of my spring/damper setup (Swift/Koni), but it felt like the rear was all over the place and transferring too much weight to the outside rear tire. I watched video of a run taken from a friend's dash cam, and I could see the rear end moving around and wanting to break loose. To me, it seems like the car wants some amount of rear bar stiffness.
• If you buy adjustable bars, the safest way to start tuning them is from an understeer bias (stiff front and soft rear). Once you understand how the car behaves in all conditions, adjust from there. Cars are designed to understeer from the factory because it generally makes limit handling more predictable. Changing this balance can drastically affect predictability.
• Some of the forum members who posted in here might be running square tire setups like mine (the same tire width all around), instead of the factory staggered setup. They may also have other modifications that affect how their car behaves. Consider this before putting the exact same settings on your car.

Roll Stiffness
Roll stiffness in the vehicle comprises at minimum four parts:
1. Springs
2. Stabilizer (sway/anti-roll) bars
3. Bushings
4. Tires

Technically, there are at least two more:
5. Mounting point stiffness (how easily the subframe and body attachments flex)
6. Bump stops (only apply at high roll and wheel deflections)

We can leave the last two out for the sake of this discussion, since #5 mainly affects suspension kinematics and compliances, and #6 only applies under high force.

Suspension roll stiffness = #1 + #2 + #3. These combine directly because they act together (in parallel). Springs and stabilizer bars generally have the highest stiffness contributions. Depending on the vehicle type and tuning, their effective rates may be equal. However, bushings can make up 10-20% of the total suspension roll stiffness in a stock suspension. The bushings include the ones in the upper and lower control arms and the dampers. Note that changing control arms to ones with spherical joints reduces overall suspension roll stiffness.

Total roll stiffness = 1 / (1 / suspension roll stiffness + 1 / #4). The suspension and the tire act like springs in series because the suspension is basically "sitting on top" of the tire. Tires are essentially springs made of air, rubber, nylon, steel (and whatever else makes up the tire carcass). Depending on the type of vehicle, the tire can be ~5-10x the suspension roll stiffness. Therefore, the tire can have a ~10% impact on total roll stiffness, up to a point. Factors that influence this include the tire width and aspect ratio, load index and rating (standard or XL), and type of tire (all-season, summer, etc.). Even the same size and type of tire from different manufacturers will have different stiffnesses, because each manufacturer has their own compound and construction. Running a higher tire pressure will also increase stiffness. The tire does not compress as much as the suspension in roll, but it is still a significant part of the equation.

Understeer/Oversteer
There are many factors that affect this behavior, and I would not claim to know them all. My comments below mainly apply to independent suspensions, as on the Z.

One contributor is the front vs. rear roll stiffness balance, which some others have talked about. This is what we can modify most easily on our cars by changing settings on adjustable bars. Generally, the higher the front roll stiffness and lower the rear roll stiffness, the more the car will have a tendency to understeer. Putting tire widths and other variables aside, my understanding of this is that the front "saturates" or reaches its maximum grip first. It becomes the limiting factor. When cornering, the center of gravity or CG of the car wants to keep going straight. It "pulls" on the car and causes it to roll sideways. The suspension and tires resist this force, and if the front is stiffer, it essentially resists more than the rear. What this means is that at the limit, the front will be the first to break traction.

Another contributor is suspension kinematic & compliance behavior.

Generally, the front suspension is designed to toe out under compression and toe in under rebound. As the car rolls, the outside suspension will go into compression, and the inside will go into rebound, so both wheels will "steer" toward the outside of the corner. This is called roll understeer. The rear suspension usually behaves in the opposite way. When a rear wheel goes into compression, it toes in, and does the reverse in rebound. In a corner, this means that the rear tires "steer" into the corner. This is also roll understeer. Why? It helps the rear axle to grip harder in a corner, whereas the opposite behavior in the front suspension causes it to lose some grip in a corner. The combined effect is understeer, which makes handling more predictable.

Finally, many suspensions are designed in such a way that the front wheels "steer" toward the outside of a corner and the rear wheels "steer" toward the inside as a result of lateral force on the tires. This is called compliance steer. The effect is more pronounced under high force, so it may not be as noticeable under normal driving as roll steer. Compliance steer also happens from front to back forces on the tires. If you go for a square tire setup with a common wheel offset like me, you will realize this when braking, as the car pulls to either side, depending on the road surface.

I hope some of this was helpful!

filip00

Bringing this up from ashes - I dunno, I think it makes more sense to continue in one place and gather knowledge, than to just open a new thread. Hope you guys agree.

So, my question... Is there any downside to running both front and rear stiff anti roll bars?

I just installed front whiteline rollbar and out of curiousity, I put both it, and my rear ARB (also whitelines) to their stiffest settings. That is paired with the KW V3 suspension, compression on a bit stiffer setting, rebound on softer. Factory tyre dimensions.
I drove around 60km of open road today, along with various roundabouts (tiny and large ones), trying out the limit, sliding a bit, doing a few powerslides to see whether I'll have snappy back or not. And to be honest, the car drives really well. I'm not sure if that's placebo, am I maybe not dialed in today, but I have a feeling like it's even better than before.
There is practically no body roll in the corner, the car is ridiculously flat, and the ride is a bit stiffer, but not harsh. When driving a medium speed corner and going too fast, if a bit on the throttle, the car wants to slightly understeer, but if I overdo it a lot, then it's gonna oversteer. Kinda reminds me of how first gen BMW M4 handle.

I'm thinking now - am I overlooking something? Maybe I'm misjudging the car and maybe there's a downside I don't see yet? I appreciate any comments.

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Averying

Im no expert and I have limited experience with actually trying different suspension setups, but this is how I’d explain it.

The total stiffness of the ARBs in the car isn’t as important as the relative ratio of stiffness between front and rear ARBs. ARBs are a tool to fine tune the understeer/oversteer characteristics.

Remember that ARBs reduce body roll, helping keep the tires in an appropriate camber window/range, BUT ALSO reduce grip at the axle which they’re installed because they put additional force on the outside tire. That’s how they reduce the vehicle’s roll.

Therefore, adding just a stiffer rear ARB to your current setup will increase oversteer compared to how your car drives without the stiffer rear ARB. This may make the car easier to rotate, or suit your driving preferences, or instead make it uncontrollably loose in the rear.

Long story short, ARBs are tuning tools. If you like how it feels with the stiffer rear ARB, keep it on!


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OptionZero

we can measure effectiveness by examining laptimes (Big picture) and tire wear (small picture)

In general, the experience of track folks is to add front bar to reduce understeer because the Z34 is too soft in front. Most found rear bar unnecessary

However, everyone's setup (including tires and other suspension parts) and driving style is different.

Test on your own, go with what works.

That's advice for driving closer to the limit. For bumming around on the street, you won't feel the difference.

I suggest digging through this:
Track Day Chat

and searching in the track subforum

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