[stretch]

I measured the lever arm on my Whiteline rear sway bar today and found it to be:

6-3/4" long at its stiffest setting
7-15/32" long at its middle setting
8-3/16" long at its softest setting

Previously, I've measured the stock lever arm at about 7" long (could someone double-check this measurement, it's crucial). The shorter this arm, the stiffer the sway bar feels in use.

Anyway, if my measurements are accurate, the Whiteline 24mm sway bar is the equivalent of 24.5mm on its stiffest setting. That's about 225% firmer than stock at the stiffest setting and just 50% firmer at the softest setting- not bad, but far from the "26mm" setting (285% over stock) Whiteline advertises.

The Whiteline bar does indeed act like a 22mm bar on its softest setting (as advertised).

Now, the second twist to the story here is that the bushing for the control arm where the sway bar connects is very, very soft. It allows for some slop, so stiffening these bushings will stiffen your sway bar more. I don't generally like the NVH from stiffer bushings, but this might be an excellent modification for stock class autocrossers.

I'd like to measure the front bar at some point, too, because I know it's rate in practice is well below what I calculate it to be. I don't know if this is due to bushing flex or because the sway bar isn't the dimensions I think it is. I know the 27mm bar (at 27mm) felt drastically softer than my 32mm hollow Strano bar.

Edit: the Whiteline 27mm front sway ratings are pretty faithful compared to stock. The reason its rate seemed lower than what I calculated is because the motion ratio is lower than I originally thought, roughly 0.66.

Here's an easy way to calculate your own sway bar rates (with a diagram showing what to measure): Weight transfer, spring frequency, damper, body roll calculator... and more!
If anybody else would like to measure their own sway bars, it'd be good to know how stiff they really are.

[maverickar15]

Thank you for the information.

So if I understand correctly, a whiteline 22/24/26 adj. rear bar is actually

22mm = 22mm
24mm = 24mm
26mm = 24.5mm

[stretch]

The "24mm" setting is evenly spaced between the other two, so it's around ~23.25mm.

Soft: 22mm
Normal: 23.25mm
Firm: 24.5mm

Although, to make this apples to apples, this would be in comparison to a stock sway bar with similar durometer urethane sway bushings (as Whiteline provides).

[twiSTies]

Very interesting. I wonder how they calculated the 26mm.

I've run the bar at full soft, then the middle setting and really didn't notice much of a difference. This helps explain it.

[mxpop]

Thats kinda like what my grampa told me.

"marry a woman with small hands, it makes your weiner look bigger"


Just like a bushing makes your sway bar stiffer?

[4banger]

Originally Posted by stretch

Now, the second twist to the story here is that the bushing for the control arm where the sway bar connects is very, very soft. It allows for some slop, so stiffening these bushings will stiffen your sway bar more. I don't generally like the NVH from stiffer bushings, but this might be an excellent modification for stock class autocrossers.

Whiteline has an article on their website that explains that there is no change in stiffness in your endlinks based on what type of bushing you are using. The only difference is how fast it reacts. The bushing will only deflect so much and then it acts as if you had a solid endlink.

[stretch]

Originally Posted by 4banger

Whiteline has an article on their website that explains that there is no change in stiffness in your endlinks based on what type of bushing you are using. The only difference is how fast it reacts. The bushing will only deflect so much and then it acts as if you had a solid endlink.

That's exactly right, but when you're talking about a bar with 310lb/in of rate (stock bar in a body roll situation), a quarter inch (1/8" per side) of total bushing deflection becomes significant! The sway could be super stiff but you'd still get the same additional body roll due to bushing deflection beyond what the sway bar is supposed to be allowing.

Put it this way: if every bushing in your car were perfectly stiff (including your tires), a stock STI would roll less than two degrees at its limit. We know that not to be true, and that's because a lot of roll comes from bushing deflection. After examining the rear control arm bushing, I see why. (I plan to start a "Where does body roll come from?" thread at some point, but not yet.)

[mxpop]

I think stretch was refering to the mounts that attaches the bar to the body. A softer/harder bushing here will impact the effective width of the mounts relative to each other which will effect its overall stiffness.

Actually, any mount will effect the bars characteristics, in various ways, depending how soft/sloppy they are.

[4banger]

Stretch - so the bushing is so soft that it defelcts so much that it never gets a chance to max out (or at least takes a long time)?

[stretch]

Originally Posted by 4banger

Stretch - so the bushing is so soft that it defelcts so much that it never gets a chance to max out (or at least takes a long time)?

My point is that regardless of which sway bar you run, your sway bar rate starts out near 0lb/in before going to what it should be. There's no initial sway bar resistance, which means the car has an allowable amount of body roll before the sway bar starts working. It's not even close to being rigidly connected the way your main springs are. That's sort of expected, but the extent of it surprised me.

[4banger]

Ahhhh. I see what you're saying, now.

[stretch]

Originally Posted by mxpop

I think stretch was refering to the mounts that attaches the bar to the body. A softer/harder bushing here will impact the effective width of the mounts relative to each other which will effect its overall stiffness.

Those are important too, but I was referring to the bushing that connects the lower control arm (lateral link) to the hub. It's made of marshmallow. Without stiffness there, the sway bar isn't rigidly connected to the wheel either.

Anyway, it was just a side thought- didn't mean to start a whole discussion on it!

[4banger]

Originally Posted by stretch

Those are important too, but I was referring to the bushing that connects the lower control arm (lateral link) to the hub. It's made of marshmallow. Without stiffness there, the sway bar isn't rigidly connected to the wheel either.

Anyway, it was just a side thought- didn't mean to start a whole discussion on it!

Sounds like a new bushing for TiC to produce.

[Turninconcepts.com]

Originally Posted by 4banger

Sounds like a new bushing for TiC to produce.

I've been thinking about that one for a good long while actually...

In fact, I did some reading recently. See, even though I read a lot about suspensions every time I pick up a new book I learn something new. Sure, quite a bit of it is old hat, and has been covered in prior books, but it seems that each one has a nice little gem to offer. Latest reading was a book I quickly read while waiting in line at midnight for the new Harry Potter book. This one discussed dynamic toe changes due to soft bushings leading to oversteer and understeer. A bit of an interesting subject, and one I never really put a lot of thought into in the past. It planted a seed in my head that perhaps I need to take a look at upgrading those bushings to see what happens.

Sure, you could have always replaced them in the past, but I've always felt that they were one of those things that one would do once all the other stuff is taken care of. You know, for those guys looking to shave the last couple of hundreths of time off. After reading about it, and doing a little more searching I'm thinking that this is something that should take place earlier in the upgrade cycle.

[lovesmysuby]

Originally Posted by Turninconcepts.com

I've been thinking about that one for a good long while actually...

In fact, I did some reading recently. See, even though I read a lot about suspensions every time I pick up a new book I learn something new. Sure, quite a bit of it is old hat, and has been covered in prior books, but it seems that each one has a nice little gem to offer. Latest reading was a book I quickly read while waiting in line at midnight for the new Harry Potter book. This one discussed dynamic toe changes due to soft bushings leading to oversteer and understeer. A bit of an interesting subject, and one I never really put a lot of thought into in the past. It planted a seed in my head that perhaps I need to take a look at upgrading those bushings to see what happens.

Sure, you could have always replaced them in the past, but I've always felt that they were one of those things that one would do once all the other stuff is taken care of. You know, for those guys looking to shave the last couple of hundreths of time off. After reading about it, and doing a little more searching I'm thinking that this is something that should take place earlier in the upgrade cycle.

Would this be a replacment for both the upper and lower bushings? Could this be a good combo with the lower trailing arm bushing too?

I would buy these if TIC made them cause I like black more than the Super Pro blue.