Sway Bar Sizes

[Earendil]

because stiffness is directly related to the diameter of the bar. bigger bar = stiffer. generally they're all made of the same sort of spring steel.

you can figure out the relative stiffness if you only know the diameter. (new/old)^4 - so a 20mm swaybar is almost *8* times stiffer than a 12mm bar. you can see how many consider such a large rear bar to be massively oversized.. that would be like increasing your front spring rates from stock to ~1300/1800#.

So if they are all the same material, why the same size front aftermarket bars?

AC Schnitzer: Front: 20mm Rear: 16mm
Eibach: Front: 20mm Rear: 16mm
M-Technik: Front: 20mm Rear: 14.5mm

That little math bit, if correct (:)) is quite a useful piece of info that I hadn't seen mentioned in a swaybar discussion before. Make me think a 22mm upgrade from 20 might actually be worth something (46% increase).

[nando]

because stiffness is directly related to the diameter of the bar. bigger bar = stiffer. generally they're all made of the same sort of spring steel.

you can figure out the relative stiffness if you only know the diameter. (new/old)^4 - so a 20mm swaybar is almost *8* times stiffer than a 12mm bar. you can see how many consider such a large rear bar to be massively oversized.. that would be like increasing your front spring rates from stock to ~1300/1800#.

[Earendil]

Stock:

318i(m10): Front: 18mm Rear: none
318is(m42): Front: 20mm Rear: 12mm
318ic(m42): Front: 21mm Rear: 12mm
325e(pre 9/86): Front: 18.5mm Rear: 12mm
325e(9/86): Front: 20mm Rear: 12mm
325i(m20): Front: 20mm Rear: 12mm
325is(m20): Front: 20mm Rear: 12mm
325ic(m20): Front: 21mm Rear: 12mm
325ix(M20): Front: 17mm Rear: 14.5mm
325ix Touring(M20): Front: 18mm Rear: 14.5mm
M3(s14): Front: 19mm Rear: 14.5mm



Aftermarket:

AC Schnitzer: Front: 20mm Rear: 16mm
Eibach: Front: 20mm Rear: 16mm
Suspension Techniques: Front: 22mm Rear: 19mm
Ireland Engineering (adjustable): Front: 25mm Rear: 22mm
H&R (adjustable): Front: 22mm Rear: 18mm
Racing Dynamics Early Style (adjustable): Front: 22mm Rear: 16mm
Racing Dynamics Late Style (adjustable): Front: 22mm Rear: 19mm
M-Technik: Front: 20mm Rear: 14.5mm

If you have more info to add, post here and i will update the faq.

Enjoy.

I'm curious what the point of all the 20mm aftermarket bars are? Are they made out of a different and thus stiffer material? And if so, why measure them in mm instead of some sort of force per distance rating?

Unless of course the multitude of 20mm bars are all for the 318?

[nando]

^ yep

[blefevre]

I guess so. Because I was searching for parts under my model and year on Bav auto, and ordered rear sway bar links but they sent me 12mm. So I phoned, and they said that's all they were showing for my car. But The PO told me I had M-tech suspension... I just thought that was standard on the is. I thought that's where the *sport* must come from. :p


By the way... I have those two 12mm sway bar links I'll give away for the cost of me shipping it to you if anyone's interested. PM me. or e-mail me at mamczasz@gmail.com

12mm and 14.5mm rear bars use the same sway bar link. The 14.5mm bar is turned to 12mm at the ends.

[88SuperETABD]

What does a 1988 325 (supereta have)? Anyone know?

[mamzak]

14.5 must have been an option, it's standard on the ix and M3.

I guess so. Because I was searching for parts under my model and year on Bav auto, and ordered rear sway bar links but they sent me 12mm. So I phoned, and they said that's all they were showing for my car. But The PO told me I had M-tech suspension... I just thought that was standard on the is. I thought that's where the *sport* must come from. :p


By the way... I have those two 12mm sway bar links I'll give away for the cost of me shipping it to you if anyone's interested. PM me. or e-mail me at mamczasz@gmail.com

[Fraser]

Anybody know what this one is? 19mm, came off of my iX and I can't figure out what it's original on... M coupe?

[nando]

14.5 must have been an option, it's standard on the ix and M3.

[mamzak]

My 318is came with the 14.5 M-tech rear sway... I thought that was a standard thing on the 318is. It was an option?

[Lunner]

I have an Addco rear sway bar on my e30, it measures 3/4" (~19mm).

They also make a front at 1" (~25mm).

[Airplanecar8]

I took the time and liberty to purchase is bars for my 89 325i. They are all the same basically. Oh well I paid 20 bucks what are they worth? I think the guy might trade me back though. hes a board member

[JakeP]

I have a 91 318i 4-dr and it came with a 12mm rear sway bar... Update the list?

[EN318isPDX]

wow, the rear seems like overkill

Its not, i have the 25mm front//22mm rear and it totally made my car! The suspension is super tight and I expected it to go sideways all the time but it doesnt unless i push it.

[MikeM]

just trying to make sure...ix rear sway bars fit on a 325i convertible correct? and then is it just a bolt on swap, easy?