Body Roll on Stock Sway Bars

[aTron12]

Few questions here:

What would you guys say I should expect to experience with the stock 1989 front/rear 325is sway bars?

I'm experiencing more body roll than I used to get when cornering, Just doesn't feel as tight as it used to. I have new control arms/bushings, Eibach springs/Bilstein HD's. Would replacing sway links and bushings make a huge difference here? The Eibach sway bars don't seem to be much bigger in diameter than the BMW bars.. or is it more the design of the bar that keeps the car upright?


Thanks,

Adam

[Sagaris]

Springs which lower the car will lower the center of gravity and the roll center. Usually the roll center drops more than the center of gravity which creates a larger moment arm/more leverage for the mass of the car to transfer laterally (body roll). If the lower springs are not sufficiently stiff then you will experience more body roll. So yes, it is perfectly acceptable to install lowering springs on a car and notice more body roll, even with the spring rates are quite a bit higher than stock. I notice more body roll with H&R sports + drop hats in the front. The solution is to beef up the sway bars or install stiffer springs.

If a stiffer metal is used or the link mounting point changes then an aftermarket but nearly stock sized sway bar could be stiffer. I wouldn't count on either of those being the case though. I am a fan of softer springs with stiff sway bars. You still get good forward/rear weight transfer and comfort but the stiff sways help keep the tires from being overloaded from lateral weight transfer.

[shiboujin]

http://www.turnermotorsport.com/p-4076-e30-turner-motorsport-j-stock-suspension-system.aspx

[blefevre]

Eibach springs have nearly the same spring rate as stock springs. You pretty much have "stock body roll". H&R sport, vert front sway bar, iX/M3 rear bar is a good starting point if you want to keep it cheap. There will be less roll, but there will still be a fair amount when you push it.

[Stoner Sam23]

I have been told that lowering springs on our cars preloads the sways making them less effective. Adjustable sway bar links should correct this and help body roll. I have not done this becuause it doesnt add up to me (maybe the front). Just a theory I am passing to you.

[aTron12]

Thanks for the input gents...

So if I were to upgrade to the Eibach sways, I would notice a significant difference even though the diameter is only slightly bigger than stock sways? I am assuming that the actual design on the bar/links is also why these bars perform better than stock?

When the springs and shocks were upgraded the same day a year and a half ago, the ride was tighter. Could they just be broken in now? Also, I'm not tracking. Just having a little fun around corners on the street. This car gets my ass to work so I can pay for my E30 sickness:)

[blefevre]

Buying H&R race will reduce your body roll much more then getting bigger sway bars.

[Sagaris]

Buying H&R race will reduce your body roll much more then getting bigger sway bars.

Honest question: Do you know that from experience or have you done any roll-stiffness calculations?

[blefevre]

I have been in a car with H&R sport and upgraded sways vs GC and stock swaybars. Guess which one had nearly zero body roll and which one had a ton on the track....

I assume he doesn't want to get a GC kit, so H&R races provide ample spring rates to reduce roll.

[aTron12]

All I'm sayin' here is that the upgrades I made were fantastic the first year. It felt like a sports car. Comfortable ride with low body roll and a hell of a lot more control than stock. I have noticed in the past few months that it is a softer ride than the first. Not looking to coilover and polyurethane the hell out of my suspension because I drive this daily. Just looking for ideas on why the roll is increasing.

These are the thoughts I have when driving:

Is it just broken in now and that's what I get?
Are there bushings that could be worn out and need replacement that I have missed?
Will a sway bar upgrade really help that much?

[blefevre]

If the springs are near their end of life, yes you will get more body roll. That shouldn't be for a long time though, but I did not design eibach springs so I'm not sure what they designed to.

There can be a little bit of "settling in" depending on the spring, but again, it shouldn't change the spring rate that much.

Sure, you can slap on huge sway bars and you will have less roll. You will need to reinforce the rear so you don't tear your bar off as it will be doing all of the work to make up for the soft springs.

I still recommend stiffer springs as it will also reduce dive in under braking and lift during acceleration which will also help handling. Sway bars will not do this.

Did you check to make sure the rear sway bar link didn't pop off? That happened to me once.

[Stephen]

The minor changes in sways are just as much for understeer/oversteer as they are body roll. But it may help.

however, the soft as fuck eibach prokit is where i'd start. Even H&R sports will likely be an imporvement, and completely dailyable

[LJ851]

All I'm sayin' here is that the upgrades I made were fantastic the first year. It felt like a sports car. Comfortable ride with low body roll and a hell of a lot more control than stock. I have noticed in the past few months that it is a softer ride than the first. Not looking to coilover and polyurethane the hell out of my suspension because I drive this daily. Just looking for ideas on why the roll is increasing.

These are the thoughts I have when driving:

Is it just broken in now and that's what I get?
Are there bushings that could be worn out and need replacement that I have missed?
Will a sway bar upgrade really help that much?

Could it be that you are just fully used to now and can't remember the way it was before?
Worn sway bar end links and worn sway bar bushings will contribute more body roll ( takes more movement to load the bar). A sway bar upgrade will help the body roll issue a lot and not change your ride quality much. Sway bars are torsion springs and their stiffness rises very quickly from an increase in size. Poly sway bar bushes will put the bar to work sooner than rubber (less roll)

If you want to retain the ride quality you have, start with big sway bars and go from there.

[aTron12]

I just gave Eibach a call and got some interesting info. The rep told me that the spring rate should not change in any way for a very long time if at all. They also engineered them to work with OEM shocks (height especially) , so we know that the HD's are okay with this setup. I checked for a blowout and found nothing.

I think that the breakdown must be links/bushings related. I would even go as far as upgrading to the Eibach sways & poly bushings on the bars/links because I have been really happy with the ride quality. The rep was saying that 1 or 2 mm difference in diameter makes an exponential difference in handling which I didn't realize. He actually said that it could be as much as 100% improved--whatever that means, it sounds like it is significant over OEM.

LJ851, I did give your question a lot of thought just now and was asking myself the same thing over the past few months and I honestly am noticing a difference. I thought it may have been because I was used to the setup and am wanting more. I have been content over the past year or so and now the handling is just plain distracting so I think this is an authentic evaluation and a real symptom. Good question to pose amongst us car tweakers:)

I'll be under the car next few days some time and hopefully have some answers.

[blefevre]

Yep, most springs should last a very long time, no surprise there. I wouldn't expect very flat handling with those springs though, regardless if you get the eibach sways. They aren't that big. They are 20/16mm. The factory is 20/12 for most cars. Why not get the IE 22/19 or suspension techniques. You are going to need a beefy bar to make up for the crazy soft springs you have. And don't forget to reinforce the rear if you insist on going big bars/soft springs.