e36 sport sway vs. e36 M3 sway bar size

[M3inNC]

I read on another post somewhere that the standard non M e36 sport front sway bar is larger in diameter than the M3 front sway. Does anyone know if this is true or not.

I installed my Bilstein PSS9 coilovers and had to use standard e36 sway bar links to attach the bar to the control arm because there is no link tab on the strut body. I figured the non M sway would fit better with the links that come with it.

[Serious]

true the sport e36 front sway is a few MM thicker than m3 front sway.

they attach to different points though.

[M3inNC]

If the mounting points are similar and I can get the bushings with the e36 bar then it should work on my M3. At least I hope so.

[FierySphere]

Stock bar sizes:
95 M3 22.5mm front / 19 mm rear
96+ M3 23mm front / 20mm rear
pre-6/92 build 325 25mm front / 17mmm rear
post-6/92 build 325 24mm front / 15mm rear
328 non-Sport 24mm front / 15mm rear
328 Sport 24mm front / 18mm rear (ETK say 24mm front, but I think my GF's 328 had 25.5mm)
318ti Sport 25.5mm front (ETK says 26mm)

With the exception of the 318ti rear (E30 style) these are all interchangable between the M3 and 325/328. The attachment points are different, but the bars are vitrually identical (except for thickness, of course)

[M3inNC]

Fierysphere, that's great information and just what I was looking for. Thanks!

[G. P. Burdell]

328 Sport 24mm front / 18mm rear (ETK say 24mm front, but I think my GF's 328 had 25.5mm)

The 328 sport front bar is indeed 25.5mm.

[Morpheustj]

Great Info.. thx All

[Moron95M3]

if you want more...click the link in my signature where we discuss this and the use of a 318 sport bar (26mm). Also you'll learn the possible fit issues...

*edit* Link is gone:

http://forums.bimmerforums.com/forum...highlight=sway

[FiberFast]

Thanks for this info. Just measured my rear sway bar on my 325is with a set of callipers, it is 18mm. I checked the vin and found I have the M-Sport suspension package. 25.5mm front, 18mm rear for my 95 325is.

[SpecialED]

Stock bar sizes:
95 M3 22.5mm front / 19 mm rear
96+ M3 23mm front / 20mm rear
pre-6/92 build 325 25mm front / 17mmm rear
post-6/92 build 325 24mm front / 15mm rear
328 non-Sport 24mm front / 15mm rear
328 Sport 24mm front / 18mm rear (ETK say 24mm front, but I think my GF's 328 had 25.5mm)
318ti Sport 25.5mm front (ETK says 26mm)

With the exception of the 318ti rear (E30 style) these are all interchangable between the M3 and 325/328. The attachment points are different, but the bars are vitrually identical (except for thickness, of course)

Thanks to FierySphere for posting the info on the OEM E36 swaybar diameters 16 years ago... it was helpful to me just recently, having acquired a '97 E36 M3 autox/track car and wanting to tweak the front swaybar stiffness just a little... the car had the OEM 23mm bar, part #31352227996; and with the OEM 20mm rear bar and 500# F and 700# R (OEM location) springs, I was pretty happy with the car's balance with a 255/40-17 Falken RT660s on 9.5"s square wheel & tire setup, but it was a *touch* oversteery, especially on cold tires. Going with an aftermarket front bar would be too much front bar increase... the softest/thinnest aftermarket front bar for E36 appears to be the Whiteline bar at 27mm.

Since I bothered to take all the pictures, thought I'd share how the 24mm non-M3 E36 application part #31351090858 differs from the '96+ E36 M3 23mm bar. I also weighed them to see the difference, because why not, I have the digital shipping scale.

Skipping ahead: After having done one autocross event with the retrofitted OEM 24mm front bar, I do like the slightly stiffer front bar rate from the larger diameter (1mm increase = roughly 4.3% larger) and the shorter ends (endlinks attach closer to the effective pivot points, increasing the stiffness of the bar, all else equal)—it was exactly what I was looking for! And scoring the used 31351090858 24mm bar on eBay for only 50 bucks shipped is cheaper than buying a pair of coilover springs or an aftermarket front bar, obviously.

The strut-mounted endlink attachment points on the M cars vs the endlink attachment points being on the control arms for the non-M E36 vehicles is the reason for the M3 application front swaybar being 1mm smaller than the standard 328 spec front bar... more info on that in this thread:
https://www.bimmerforums.com/forum/s...vs-non-M-style

Here's the two bars compared... you can see how they're similar in shape but definitely not the same:






In these next two pics, you can see how the endlink attachment point is about 3/4" different between the 24mm and the 23mm bars:






Bar diameter differences... roughly 22.8mm vs 23.8mm, depending on the paint thickness:






In this pic, you can see how the clearance to the oil pan is less with the 24mm non-M bar:




But the minimum clearance to the P/S cooling hard pipes is still sufficient when the bar is rotated to its closest position:




The weight difference between the two setups is negligible... the 24mm bar is slightly heavier at 11 lb., 2.8 oz. vs 11 lb., 0.4 oz. for the 23mm bar (both weighed with the OEM bushings and mounting brackets). The 24mm swaybar comprises less material (in overall length, before bending) because of the central section having less drop and the ends being shorter:






And here's a pic of the long M3 OEM endlink, which is approximately 9" pivot point to pivot point:

[RBNetEngr]

The Eibach sways for E36 M3 are 26mm Front, 24mm Rear. I have them on my ‘95. I think they are no longer available from Eibach, but there may be some still left on the shelves at some retailers.


-rb

[SpecialED]

The Eibach sways for E36 M3 are 26mm Front, 24mm Rear. I have them on my ‘95. I think they are no longer available from Eibach, but there may be some still left on the shelves at some retailers.

-rb

Nice, good info; my web searching in late 2021 didn't turn up the Eibach front bar @ 26mm as an option, but you're right, there's probably some still available—somewhere.

Still, 26mm would be a substantially stiffer bar than 23mm, all things being equal (which of course they aren't... stiffness of the bar material, the bar end lengths, the exact curvature of the bends, etc.)

http://www.gtsparkplugs.com/Sway-Bar-Calculator.html

I really didn't want much of an increase in rate from the 23mm OEM bar as the F/R balance and turn-in characteristics with it on my car were (IMO) close to ideal.

[RBNetEngr]

The 26mm Eibach bar has three adjustment holes on each end, so the stiffness can be adjusted. With my stock suspension I just installed both front and rear bars set to full Soft, since they already added stiffness over the stock bars. Those settings added some roll stiffness, not did not increase one-wheel bump stiffness in a negative way, and did not increase understeer.

With the new ST coilovers that I recently installed, I may end up testing some swaybar settings, depending on how the coilovers change the handling of the car. Spring rates increased quite a bit over stock (especially in front).

I am of the school of thought that spring rates should be selected to accomplish most of what you want to achieve with the suspension, and then swaybars fine tune the suspension. My car is 99% street/spirited driving, so I wasn’t willing to sacrifice the ride for 99% of its use in order to greatly improve that 1% for the track.

My new coilovers, with adjustable damping, will allow me to tune the handling for the track differently than for the street, so that will let me increase the level of performance at the track, too.


-rb

[SpecialED]

Since almost no aftermarket swaybar manufacturer publishes data on the +/- % rate change of the adjustment hole positions vs the OEM bar, or even how the hole positions compare distancewise to the pivot point vs. the OEM bar's hole position, with any swaybar change, it's always a "try it and see" experiment to see if the bar works well with your setup, usage, and driving style.

Among the local autocrossers who are fast in E36s, I've had more than one driver warn me about going too stiff in front with an aftermarket bar (they'd bought them, experimented with different settings/tried to make it work, but went back to OEM)... the vast majority of aftermarket swaybars are intended to make a significant change in the how the car feels with that single part/upgrade... that's why the size and rate increases of aftermarket swaybars are often too high to complement a car with modified suspension that's specifically intended for autocross and/or track use.

I am of the school of thought that spring rates should be selected to accomplish most of what you want to achieve with the suspension, and then swaybars fine tune the suspension.

I don't disagree with that. As I said, I was only looking to make a subtle tweak to the car's balance without degrading the overall feel and grip compliance, and with the 500#F and 700# R spring rates I'm currently running, I didn't want to raise the front spring rates by 50 or 75 lb/in to try to tame some occasional oversteer in slaloms and fast offsets.

This is the car earlier this year when I had 600# rear springs... it was just a touch on the understeer-y side, especially for autox duty, hence the bump in rear rate. I'm just trying to make minimal adjustments, one at a time, to home in on the setup that feels ideal to me:

[propcar]

I've been using Non-M front bar with non-M end-links mounted to control arm for something like 6 years on my TRM setup, it was the recommended front bar configuration. Mostly I think due to the attachment collars for M swaybars not being an effective solution on many threaded strut type setups.

Front end feels great.

[M3C]

Anyone has info on the stiffness difference between the E36 M3 (red paint marks/stripes) vs. E36 non-M (blue paint marks/stripes), most likely there is some stiffness difference due to geometry difference and possibly steel composition difference.
So not sure yet but if one is thicker diameter does not indicate it is stiffer.

[RBNetEngr]

Are you asking about swaybars?

Bar thickness is a prime factor in detract bar stiffness. The thicker the bar, the stiffer it will be. Second is the length of the lever arm on each end, because that’s the lever that is putting the twisting force on the bar.

I believe that all stock bars are solid, so comparing two solid bars, the thicker bar will be stiffer.


-rb

[M3C]

Are you asking about swaybars?

Bar thickness is a prime factor in detract bar stiffness. The thicker the bar, the stiffer it will be. Second is the length of the lever arm on each end, because that’s the lever that is putting the twisting force on the bar.

I believe that all stock bars are solid, so comparing two solid bars, the thicker bar will be stiffer.


-rb

Yes, if they are the same steel material with same strength rate. Geometry is also the factor as you specified. It is strange why would BMW put a thicker version on a non-M car.

[SpecialED]

I covered why the E36 M3 front bar is thinner than on some non-M E36 applications...

The strut-mounted endlink attachment points on the M cars vs the endlink attachment points being on the control arms for the non-M E36 vehicles is the reason for the M3 application front swaybar being 1mm smaller than the standard 328 spec front bar... more info on that in this thread: https://www.bimmerforums.com/forum/s...vs-non-M-style