128 M Sport Front Sway Bar Hollow or Solid?

[Kgolf31]

Pretty simple question, which I have a hard time finding out.

Is the 128 M Sport Front Sway Bar hollow or solid?

I know the dia = 26.5mm, which makes me feel that any upgrade to H&R is minimal, because you only have a 0.5mm difference...even with the 4th root taken into effect.

But, I know for a fact that the H&R is indeed solid, which then there is a massive difference in size, and thus a good upgrade choice.

I guess this question applies to the 28mm M3 Bar, is that hollow as well?

[128Convertibleguy]

Originally Posted by Kgolf31

But, I know for a fact that the H&R is indeed solid, which then there is a massive difference in size, and thus a good upgrade choice.

It depends on the wall thickness of the hollow bar, but the difference may not be so massive (that 4th power deal). Remove the inside 50% by diameter of a bar, the stiffness changes by about 5%. It's the equivalent of shrinking the bar by about half a mm. A hollow antiroll bar is not thin tubing, it generally has a pretty thick wall.

So - do you know what the wall thickness of the hollow bar is? It's crucial.

[Kgolf31]

Originally Posted by 128Convertibleguy

It depends on the wall thickness of the hollow bar, but the difference may not be so massive (that 4th power deal). Remove the inside 50% by diameter of a bar, the stiffness changes by about 5%. It's the equivalent of shrinking the bar by about half a mm. A hollow antiroll bar is not thin tubing, it generally has a pretty thick wall.

So - do you know what the wall thickness of the hollow bar is? It's crucial.

No clue, that is why I'm trying to figure out...so I can calculate differences.

Anyways, I saw this on turner motorsports:

http://www.turnermotorsport.com/t-te...sway-bars.aspx

It says that at least the E9x Non-M has a bar that starts at 26.5mm to 23mm in the middle....so is this the case for the E82 M Sport or is it consistent 26.5mm throughout the whole bar?

[John_01]

There will be a fairly big difference between the stock bar and the 27mm solid one. I think you are right to identify the big issue as the tapered section in the middle. I recall my stock E82 sway bar has the center tapered to 23mm, and the bar that comes with the "BMW Performance" suspension kit is also 26.5mm, but tapered 1mm less, ie. tapered to 24mm in the centre. There is a noticeable difference in stiffness between those two, so it explains why the straight 26.5mm M3 bar is a significant upgrade.

The E93 M3 bar is 28mm thick, but it tapers in the centre section.

[128Convertibleguy]

Originally Posted by John_01

There will be a fairly big difference between the stock bar and the 27mm solid one. I think you are right to identify the big issue as the tapered section in the middle. I recall my stock E82 sway bar has the center tapered to 23mm, and the bar that comes with the "BMW Performance" suspension kit is also 26.5mm, but tapered 1mm less, ie. tapered to 24mm in the centre. There is a noticeable difference in stiffness between those two, so it explains why the straight 26.5mm M3 bar is a significant upgrade.

The E93 M3 bar is 28mm thick, but it tapers in the centre section.

Tapered middle sections do seem to be a major change in stiffness. Does anyone besides BMW do it? The only reason I can see for it is fewer different parts needed for different sized bars. On my list of things to get rid of.

[Kgolf31]

Originally Posted by John_01

There will be a fairly big difference between the stock bar and the 27mm solid one. I think you are right to identify the big issue as the tapered section in the middle. I recall my stock E82 sway bar has the center tapered to 23mm, and the bar that comes with the "BMW Performance" suspension kit is also 26.5mm, but tapered 1mm less, ie. tapered to 24mm in the centre. There is a noticeable difference in stiffness between those two, so it explains why the straight 26.5mm M3 bar is a significant upgrade.

The E93 M3 bar is 28mm thick, but it tapers in the centre section.

Good to know that it is indeed tapered and a solid bar will help.

Looks like I'll go H&R 27mm

[Kgolf31]

Decided to order this bar:

http://www.ecstuning.com/BMW-E82-128...Bar/ES2562637/

Sub $200 and 27.78mm, I'll take it

[Joaco135]

I'M running Hotchkits 32mm bar and love it.
http://www.hotchkis.net/bmw-e90-e92-...-sway-bar.html

[Kgolf31]

Originally Posted by Joaco135

I'M running Hotchkits 32mm bar and love it.
http://www.hotchkis.net/bmw-e90-e92-...-sway-bar.html

Are you running on stock suspension?

I'm worried that 32mm might be too much, and cause excessive wheel lift. I'll be running #400 fronts, #700 rears.

As well, it is nice that they include adjustable endlinks...but it sucks you can't buy the bar without getting those.

[Joaco135]

I'm running eibach springs on stock shocks, bought mine slightly used without the end links from a forum member that parted out his car. Handles very good...

[Fidiman]

I would say hollow sway bar.

I cannot find the thread on the board where I red it, but a solid bar is almost 50% heavier and only 10 or 15% stiffer ...

A friend of mine who does a lot of tracking at the Nürburgring installed the front and rear anti-roll bars of the e93 M3 and said to me it was better than choosing the e92 one (but stiffer the car alot) !

So if I were you, I would order a M3 e93 anti-roll bar

[Kgolf31]

The problem with OEM bars is that they narrow down in the middle. So going to a solid, but continuous dia bar changes more than 15%

[Fidiman]

That's only for the OEM e82 bar and for the e93 m3 bar. For the e92 m3 bar, that's a 26,5mm continuous bar.

IMO, the increase of stiffness is for a given diameter which is the same for the two bars (the hollow and the solid).

Sorry for my bad explanations. I should find the thread I spoke about before



Edit : Here it is mate
But we should now the diameter of hollow bars ...

[mlifxs]

Originally Posted by Fidiman

I would say hollow sway bar.

I cannot find the thread on the board where I red it, but a solid bar is almost 50% heavier and only 10 or 15% stiffer ...

A friend of mine who does a lot of tracking at the Nürburgring installed the front and rear anti-roll bars of the e93 M3 and said to me it was better than choosing the e92 one (but stiffer the car alot) !

So if I were you, I would order a M3 e93 anti-roll bar

I agree on the weight issue. I weighed a H&R bar for the 3 series, it was nearly double weight of the sport package bar.

Not sure about stiffness, but I do like it.
http://www.e90post.com/forums/showthread.php?t=880862