Sway bar size suggestions.

[camshaftgsxr]

alrighty! so now that the "basics" of my suspension are done, i need to begin thinking of sway bars... and i have no idea where to start, most of the threads i have found are dealing with cars on 200-400# spring rates, my assumption is that stiffer springs mean thicker/stiffer sway bars. i could be wrong about this and it wouldnt be the first time, but the forum is for learning... so learn me!

right now as the car sits,

89 325is, m20b25, 4 lug.

Ground Control e30 "serious" track/race kit. 585# front springs 750# rear springs, with koni yellow single adjustable "race" shocks (i dont know if there is a difference but thats what the label says).

all bushings and mounts are AKG 75d red poly: m3 CABs, subframe, RTABs, motor/trans mounts. (diff mount bushing is the blue "street" bushing)

as soon as IE gets their strut bars back in stock i plan to buy both front and rear. however, the one thing i see my car lacking is sway bars, right now the front bar is stock and the rear bar is missing. even with the springs being fairly stiff i can still notice some body roll and i realize that ill never get rid of it all i fell like it can be reduced and the handling improved by installing some thicker sway bars. i just dont know where to start with sizing for my application.

so.. what sway bar sizing does R3V recommend to compliment my current suspension? please note the car is technically a street car and i do drive it almost every day, so anything super high maintenance is a no go for me. but noise vibration and harshness are a non issue.

[jlevie]

For those springs I'd go with 25/22mm sways for track use. But 22/19mm sways (especially the Bimmerworld parts) would be acceptable on the street.

You aren't going to see much, if any, affect from a front strut bar and absolutely none from a rear strut bar. The rear shock towers only carry shock loads and movement of them doesn't affect rear wheel geometry. The biggest advantage of a front strut bar is that it may keep the strut towers from moving if you hit something.

[camshaftgsxr]

Thanks for the reply, ill scratch the rear strut bar, the front bar is more of a structural support for keeping the strut towers from fatiguing and cracking up than it is for handling IMO.

Between the 25/22 and the 22/19 what would be the handling difference between them? And are there any other requirements I would need to meet in order to take advantage of the 25/22 bars? Like tires/chassis mods/etc..

[redlightpete]

You aren't going to see much, if any, affect from a front strut bar and absolutely none from a rear strut bar. The rear shock towers only carry shock loads and movement of them doesn't affect rear wheel geometry. The biggest advantage of a front strut bar is that it may keep the strut towers from moving if you hit something.

Kind of a thread hijack, but I made a gauge of sorts out of conduit between my front strut towers to see how much relative movement there was. Even at track days, the movement was minimal, maybe +/- 2mm. That's not going to change camber much. I guess maybe there's some overall improvement to chassis torsional stiffness, but this would seem much more likely if the strut bar tied into the firewall.

[camshaftgsxr]

Kind of a thread hijack, but I made a gauge of sorts out of conduit between my front strut towers to see how much relative movement there was. Even at track days, the movement was minimal, maybe +/- 2mm. That's not going to change camber much. I guess maybe there's some overall improvement to chassis torsional stiffness, but this would seem much more likely if the strut bar tied into the firewall.

i'm planning on doing to hopefully brace and correct 24 years of metal fatigue, plus i mean they look cool (kidding they are in the way all the time)

[jlevie]

Between the 25/22 and the 22/19 what would be the handling difference between them? And are there any other requirements I would need to meet in order to take advantage of the 25/22 bars? Like tires/chassis mods/etc..

If building this to be a race or track car one wants a lot of roll stiffness, which comes from stiff springs (which you have) and big sway bars. On the street either sway bar set is going to work well as you probably can't (certainly not legally) drive the car to the limit.

Well obviously stickier tires are going better take advantage of the suspension as will an increase in front & rear camber. You could throw a set of Toyo R888's on the car, which work really well in the dry and are decent in the wet, but they won't last long at all. Perhaps at most a few thousand miles. In like manner more camber helps a lot, but it wears tires fast.

Everything one can do to improve handling of a race car can be applied to a street car. But those things have a price that matters not on a race, but does matter on a street car. You have to decide where the priorities are.

[Smelser]

No sway bar at all.

Running in a dirt track. Both ft and rr sways are removed. It allows the body to roll nicely and transfer the weight to the right rear to get some bite and drive off the corner!

Sway bars????? I don't need no Fn sway bars.

[cyrmanj]

Hi camshaftgsxr and all,

Hope you are doing well, I am curious about your current dilemma since I also want to grab a sway bar kit for my E30. Which sway bar kit/width did you choose? Any specific brand you recommend.

My E30 is a daily driver, however I really enjoy occasional track days. Current set up is: budget M20B27 stroker, Bilstein sport + H&R sport springs (I believe the rates are 180 front, 380 rear) + OEM sway bars (I believe 20mm front, 13.5mm rear) + Bavauto front towers strut bar.

^ Which would be a recommended set up to complete my predominantly street/DD car?
1. Bimmerworld (22mm front, 19mm rear) $450
2. Turner (22mm front, 19mm rear) $360
3. Eibach (20mm front, 16mm rear) $349
4. UUC (22mm front, 19mm rear) $440
5. Ireland mildest offering (22mm front, 19mm rear) $440

^ Any issues or preference amongst the brands mentioned?

Thanks,

[jlevie]

The geometry of the Bimmerworld sways is better and they are effectively stiffer. They are my choice. My second choice would be the IE sways.

[mccor023]

I assume when you say turner you mean the ST kit?

Thats The kit I went with but from Blunt, I strictly DD also an have been happy with the product. I have my 1st autox event next week though. I choose them because of price, its a complete kit (-front end links), and good reviews from here.

[george graves]

There is also addco bars.

1"(25mm) front and 3/4"(19mm) rear

http://www.summitracing.com/search/product-line/addco-performance-anti-sway-bar-kits/year/1989/make/bmw

[cyrmanj]

The geometry of the Bimmerworld sways is better and they are effectively stiffer.

Thank you sir, too rough for street use? I know it is a bit subjective question but any additional feedback would be appreciated.

I assume when you say turner you mean the ST kit?

Yeap, Suspension Techniques. Thanks for the feedback, sounds like a good option for a DD, price-wise it´s also a good option. :p

[jlevie]

Thank you sir, too rough for street use?

No. Spring rates are what primarily affect ride quality, not the sways.

[cyrmanj]

^ Got it, thanks again...

[acolella76]

I have 21mm bar in the front, no bar in the rear. Might go back to stock bar in the rear though... but at the moment I'm really happy with the way it handles.