*Actual* anti-roll bar dimensions?

[tracer bullet]

I recently purchased a used set of sway bars, 26.5mm front, 20mm rear. Out of curiosity I measured them with a caliper, and saw that the front bar measured about 26.7mm, which made sense given the paint / powdercoating on them. However the rear measured about 22.7 or so, and I was very surprised by that.

The stickers all over the bar (several) said it was the 20mm part number. I measured in multiple places and it was uniform, so no 20mm tapered areas that I could find. I'll install the bar, and this isn't intended in any way to knock the seller (who was awesome and sent me exactly what I ordered, very quickly, with full pics in the ad, etc.).

I'm just hoping someone else will be curious enough to measure their "20mm" bar and see if it's truly 20mm or not. This would change what we think we know about the bars... Did this particular bar get mislabeled by BMW way back when? Or are they simply not 20mm as we think?

[MilehighM3]

Are these from an E92 or E93 M3? Just curious....if you have the part number I can tell you hat they fit, if they're OEM parts of course...

[tracer bullet]

31352283515 = Front, E92 M3, coupe = 26.5mm per the internet and also as measured

33552283655 = Rear, ?, ?, ? = 22.5mm as measured

I thought 33552283655 was the Rear E92 M3 coupe, but perhaps not? Real OEM says that's what it's for. Also seeing that realoem has it listed as 22.5mm, which is correct: http://www.realoem.com/bmw/showparts...11&hg=33&fg=45

I have the bars, bushings, brackets, etc. so I'm good on that. Just wondering what the heck I have. 'Cause it sure isn't 20mm like we always see posted and written over and over again.

[MilehighM3]

Ok I'll get them tomorrow morning for you along with the specified dimensions

[tracer bullet]

Cool, thanks. I have a feeling that all the times the 20mm thing has been copied and pasted it's actually been different.

Would love to see someone else measure theirs as well, make sure I'm not crazy.

[Xaeryan]

Originally Posted by tracer bullet

Cool, thanks. I have a feeling that all the times the 20mm thing has been copied and pasted it's actually been different.

Would love to see someone else measure theirs as well, make sure I'm not crazy.

I'll measure mine soon as I get it (next few days).
Where'd you order yours from? EDIT: Oh, you got it used.

[MilehighM3]

The 515 pn is a E90/92 E82 (1M) front bar- 26.5mm. The 655 pn is a E90/92 rear bar which is 22.5mm according to the parts catalog. Thats direct from the manufacturer. ;-)

[Xaeryan]

Originally Posted by Bmw135er

The 515 pn is a E90/92 E82 (1M) front bar- 26.5mm. The 655 pn is a E90/92 rear bar which is 22.5mm according to the parts catalog. Thats direct from the manufacturer. ;-)

He's right. I wonder if all the sites just have it listed wrong for some reason. Did anyone ever really get a 20mm sway bar from some other model and somehow it got confused with the E90/92 M3 rear sway? Are people's reviews of rear sways with a true 20mm, or 22.5 mm?
Out of curiosity, are the 20mm stickers you see on it BMW stickers or vendor stickers?
For your reference, the 1M's bar is also 22.5 - although it's a different part number so who knows what the stiffness comparison is. Of course, the 1M also comes with a slew of different parts that all work in harmony, including that wonderful LSD, so YMMV...

[MilehighM3]

The 1M does have a rear bar that is 22.5mm, but it shows a different part number. For some reason it's about $50 cheaper at retail, but none in the country. Same size as the E90/92 M3 bar, uses the same bushings as the M3, but cheaper. Hmm... Or there's the E93 M3 bar that's 23.6mm, which is also $50 more than the 1M bar. Choices, choices....

[Xaeryan]

So, I just measured my "20mm" rear sway bar, and yup it's slightly over 22.5mm in diameter. I bought this based on user feedback with similar setups - hopefully their feedback was based on the same mislabeled 22.5mm (actual) bar...

[tracer bullet]

Neato. Such is the internet, one wrong piece of information shared over and over again.

It's a safe bet that other's reviews were of the same bar, and the 20mm description has been wrong for a very long time. No guarantees obviously but I'd think it's more likely than for BMW to have changed it along the way (or even to have mislabeled it).

BMW135er - thanks for checking!

Xaeryan, the sticker question if you were asking me - they appeared to be stickers put on the bar by BMW, or by their supplier. They didn't look like a sticker that a place such as HPA might apply.

LOL any time I see someone write "20mm", I'm going to be compelled to tell them it's 22.5mm. It certainly changes things up a little bit when trying to compare bars to each other, not to mention the additional shape differences that play a role as well.

[MilehighM3]

No problem! Sorry to high jack this thread but.....

For those of you with the rear bar installed, how does the car drive? I think I need to order and install one myself next. I have a lot of suspension mods, and the car really understeers on the track. My current setup is Dinan stage 1, M3 front arms and guide rods, E93 sway bar, M3 rear subframe bushings, upper control arms and guide rods, LSD (which I know is technically not a suspension mod) and I'm running apex arc 8s w/PS2s- 245s up front and 265s out back. I'm right at -1.5 on camber up front. I just don't want the understeer to get worse with the bigger rear bar. I would probably go E93 rear bar since it's 23.6mm. It seems the car has a considerable amount of body roll for the mods, which did get worse when I went to the wider tire setup. it's either that or I ditch the Dinan and go coil overs. I would also consider Dinan M3 springs...thoughts any one? I may start a new thread....

[tracer bullet]

Intriguing. If there was a list of things to do to eliminate understeer you are pretty much there.

Something I don't understand about this car is the behavior of the rear bar (I have mentioned elsewhere, my car is now on it's way to me but I don't have it in my possession yet, so it's all based on reading). Normally a thicker rear bar stiffens up the rear and reduces understeer (or perhaps it simply promotes oversteer and these are incorrectly considered the same?). It sure was that way on my last 2 cars. For some reason it's the opposite with the 1 series, and I have yet to know why.

I would start a new thread... I think this one's run it's course, it seems proven that the rear E92 M3 coupe bar is in fact 22.5 not 20mm so I dont' care at all if it's posted here. But I'd start a new one because no one will see your question at the bottom and it's certainly an interesting one.

[tracer bullet]

Harold has updated the HPAshop web site Gotta give him credit for being on top of things (as well as an awesome vendor who I've already purchased from twice now).

[nordique14]

I have the E93 and E92 rear bars. I have not measured them but I m pretty sure there is more than 1mm of difference between them. So if the E92 bar is 22.5mm then the E93 is likely more than the claimed 23.6mm

[MilehighM3]

Originally Posted by tracer bullet

I would start a new thread....

Done... Thanks

[Xaeryan]

Originally Posted by nordique14

I have the E93 and E92 rear bars. I have not measured them but I m pretty sure there is more than 1mm of difference between them. So if the E92 bar is 22.5mm then the E93 is likely more than the claimed 23.6mm

Any chance you could measure them for us? It'd be great to clear this up in your very detailed sway bar odyssey thread as well.

[nordique14]

Originally Posted by Xaeryan

Any chance you could measure them for us? It'd be great to clear this up in your very detailed sway bar odyssey thread as well.

I suppose this is a good excuse as any for me to finally buy a caliper. Let me pick one up and then report back.

[nordique14]

just measured the E93 rear bar with a good set of calipers. 23.9mm

The E92 bar I have is the one on the car so measuring it will have to wait until I take off a wheel.

[tracer bullet]

Sounds about right for the rear bar, giving a little for paint / powdercoat. Thanks for looking at it.

Seems it's just the rear E92 bar that is different than we always thought (though it does appear to match what BMW claims for it).