Installed OEM e93 front sway bar (28mm)

[arrutled]

buenos suerte y gracias!

[Bimmer-Bob]

Originally Posted by vitig

I aligment today, camber -1,5º in all whells.Toe front -0,10º and rear +0,10.I go to a small circuit in next days and i make a test whit stock bars ,stock rear-m3 front and couple of m3, i will writte my impresions.

Which track are you going to? I looked into track days at Circuito de Jerez, but it seems they only do moto days there...

[ianc]

There must be some sort of correlation between the diameter of kink/length of kink and stiffness, although i cannot find any info on it.

I can't quote you formulas from my college engineering textbooks; that's been long forgotten 20 years ago. However, the thinner the necked section is, and the longer that section is, the less resistance to angular displacement (torsional rigidity) it will exhibit, and hence the softer the bar will seem...

ianc

[JimD]

The moment of a solid steel shaft (the amount of moment resulting from stress) is phi divided by 16 times the shear stress times the diameter cubed. So if you wanted to see what sort of difference the neck down makes, measure the two diameters, cube them, and compare. I suspect it is quite a difference.

[arrutled]

Originally Posted by JimD

The moment of a solid steel shaft (the amount of moment resulting from stress) is phi divided by 16 times the shear stress times the diameter cubed. So if you wanted to see what sort of difference the neck down makes, measure the two diameters, cube them, and compare. I suspect it is quite a difference.

assuming the ID's are the same yeah. its easier to compare OD^4 though. the real questions is: is a sway bar only as stiff as its weakest link?

[ianc]

is a sway bar only as stiff as its weakest link?

Yes, depending on the size ratios of the thick\thin sections, the lion's share of the deflection will occur at the thinnest section,

ianc

[billspreston]

Originally Posted by ianc

Yes, depending on the size ratios of the thick\thin sections, the lion's share of the deflection will occur at the thinnest section,

ianc

So the E90 vs. E93 are essentially the same then??

[ianc]

So the E90 vs. E93 are essentially the same then??

I don't know the sizes of those bars so I couldn't say. It's important to note that deflection is not localized to the necked section however, it occurs all through the bar. It's just that the necked-down section will deflect MORE than the larger section. What the relationship actually is depends on the relative ID, OD, and lengths of the two (or more) sections however. It is also true that the relation involving the ID and OD of the bar's sections is not linear. Jim states above that it's related to the cube of the diameter, although since these bars are hollow, it may be (OD-ID)^3. I don't have the formulas to hand...

ianc

[BMW86]

Sorry to jack this thread... What would be a better to do first with KW V2's? E93 sway bar or tension rods and wishbones?

[arrutled]

Originally Posted by BMW86

Sorry to jack this thread... What would be a better to do first with KW V2's? E93 sway bar or tension rods and wishbones?

You need to do both, they compliment each other well.

[billspreston]

Originally Posted by BMW86

Sorry to jack this thread... What would be a better to do first with KW V2's? E93 sway bar or tension rods and wishbones?

I would say V2s because of the stiffer springs, but I'm no expert. I'll be doing V2s and sway bar (E90) at the same time, probably this weekend.

Edit: ^^ What he said

[ianc]

What would be a better to do first with KW V2's? E93 sway bar or tension rods and wishbones?

I agree with Andy that you should do both eventually, but if you already have V2's, your springs are probably quite a bit stiffer than the stock marshmallows, so your body roll is probably more under control than it was. With that, I would probably do the M3 bits first to add more steering precision and feedback, and the sway bar later.

The bar is so easy you can do it in a half hour in your garage...

ianc

[BMW86]

I'm leaning towards the sway bar mainly because of the positive reviews and the cost factor. I'm assuming by the time I buy it, ship it and install it, I'll be up for around $400-$450 to have the sway bar in my car. The front control arms will add on another $500 or so.

[arrutled]

sounds like someone already had their mind made up, lol. But if I had to pick which one to do first I would do the sway bar. I did the M3 bits first. They only slightly improved my ability to control the car. The sway was a more drastic improvement in handling.

[ianc]

The front control arms will add on another $500 or so

Don't forget to factor in the cost of an alignment with these...

ianc

[TimMc]

Originally Posted by BMW86

I'm leaning towards the sway bar mainly because of the positive reviews and the cost factor. I'm assuming by the time I buy it, ship it and install it, I'll be up for around $400-$450 to have the sway bar in my car. The front control arms will add on another $500 or so.

G'day 86.
PM me about this. We live in the same town & it looks like we're looking for similar gear. I'm contemplating an E92 M3 front bar and perhaps the M3 front control arm kit. Just emailed about shipping costs.
Cheers, Tim.

[AussieRacer]

If you're after feel and precision, I'd do the front wishbones and tie rods well before the sway, if you are already doing K2s. IMO, they will have the biggest effect. I did the M3 bits in three stages: rear links (not bushings though); then front links; and finally sway. Whilst the sway was a great addition, front links changed the front the most. I am running stock springs and shocks though as wouldn't change that at all. Links themselves stiffen things up.

[TimMc]

Originally Posted by AussieRacer

If you're after feel and precision, I'd do the front wishbones and tie rods well before the sway, if you are already doing K2s. IMO, they will have the biggest effect. I did the M3 bits in three stages: rear links (not bushings though); then front links; and finally sway. Whilst the sway was a great addition, front links changed the front the most. I am running stock springs and shocks though as wouldn't change that at all. Links themselves stiffen things up.

Sounds like I might be heading down your path Aussie. I don't plan on changing springs and shocks at the moment. Mine's a daily driver that I'd just like to handle a little better at the track and through the mountains.
Where did you source you gear from. 'Just got quoted US$344 by HP Autowerks to freight the M3 Front Control Arm Kit and E92 M3 Front Antil Roll Bar kit to Brisbane.

[bmw13]

i am on stock suspension, i have 235 up front and 255 in the rear, is the 28mm bar too stiff for my setup, i dont want to make the wrong decision, thanks in advance. ps. really do respect you guys who know your stuff, liking the answers with solid explanation and reasoning to support as well

[Cuz5150]

Does anyone have the torque specs on the sway bar bracket bolts and end links?
Can someone please post

Thanks

[ianc]

Droplinks are 58 NM. Can't remember the brackets, but it's nothing much. I think you'd be safe with ~20 NM...

ianc

[AussieRacer]

Brackets are 21Nm. Which you really need a smaller 3/8" torque wrench to accurately measure. And yeap, stabiliser links are 58Nm top and bottom. You'll need lock-pilers or the special tool to tighten those.