1 sway or 2 sway?

[EnzoRWD]

I was planning on getting a set of stech swaybars for my s13 coupe, but recently have thought about going a pieced-together plan.i might pick up an R32 rear bar that supposedly fits, and its quite large. (exhaust clearance issues?)in addition to that, i might get a k's front bar. is running stock front, R32 rear a good idea? or is the stech setup better anyways?btw- this is for road race not drifting...-Enzo

[Q45tech]

Depends on how much rear roll stiffness you want?A rough rule of thumb is a 20 mm rear bar [with a 6" arm] adds [resists] roughly 40 pounds per inch of body roll to the wheel rate of roughly 110 pounds per inch.

The other rule is don't have a bar stiffer than the springs [roughly 24 mm].

Ideally, I believe something in the 21-23 mm range would be close even with something like Eibach lowering springs......assuming you leave the front bar oem stock.

Obviously everyone will like a differing amount depending upon their skill level in driving near the edge of dry neutrality.

I use 20mm rear with Eibachs on my Q [very very similar rear suspension design and similar spring rates but obviously more weight].

[eddiec]

the hicas rear bar is 21mm. might be cheper alternative. hicas cars also had 25 front if memory serves me right.

depending on the r32 size it may be too much. r32 being heavier and prob came w/ stiffer spring rates so need a bigger bar (just guessing).

but it could be fun. i saw a vw bug running a big bar at an a/x last year and it was all they could do to keep the back end from coming around in corners or the slalom.

[Chingon]

I've thought of a cheaper alternative but don't know if it'll work.

There's this polymer based foam that ranges in stiffness from foam-like insulation, to wood hardness, to concrete-like. My idea consists of filling the hollow tube OEM swaybars w/the concrete type to similate what a solid bar swaybar would do. This is what i'm doing this summer, and I think it may just work. I'll get you pricing, and webpage if interested on the product.

[eddiec]

you talking about this stuff??http://www.itwfoamseal.com/auto_aftermarket.htm

if so tell us how it went. ive been thinking of putting it in the frame rails to stiffen the chassis. but the price is holding me back.

[eddiec]

and somewhere i read recently said the inside of a sway actually does zero work. sounds far fetched i know, but the article went on to say that the majority of the work (resisting flex or sway) is done by the outside walls of a bar. and that a hollow center helps reduce weight.

[whiterps13]

most aftermarket bars are hollow, to reduce weight. i dont think you would want a concrete-like anti roll bar though.

[Chingon]

I'm pretty sure the whitelines are solid aren't they? And remember that aftermarket go w/a bigger diameter, this fixes the problem of having to go solid while saving weight. What I want to save is money. And that kit seems similar to what I'm looking at, except it's like 15 dollars the gallon compared to that. I'll look it up in a sec.

[Chingon]

from pdm about whitelines "....These are high tensile solid steel bars (unlike hollow Nissan OEM bars) ..."

[Chingon]

This is the website I'm talking about....they have really cheap carbon fiber fabric and resins for those inclined enough.

http://www.shopmaninc.com/foam.html

I would go w/the 16 lbs or the 8 lbs kit I would guess.

[Chingon]

and somewhere i read recently said the inside of a sway actually does zero work. sounds far fetched i know, but the article went on to say that the majority of the work (resisting flex or sway) is done by the outside walls of a bar. and that a hollow center helps reduce weight.

That kinda seems odd don't ya think.....I can't physically comprehend it.

It's like saying that a hollow tube is as easy to bend as a solid bar of steel you know? Have you tried bending a tube vs a bar...?That's the logic I see behind it.

[eddiec]

i still find it hard to believe. but then again i was only an engineering major for one semester. maybe someone more qualified can chime in.

thanks for the link to the stuff.

[Chingon]

well, they make custom car frames out of hollow tubing, but the design (triangulated construction usually) is what makes the frame strong.

Again I'm kinda going but what whiteline did. If so many ppl are happy w/them, they must've done something right (although they did increase the bar diameter as well).

[deezlins]

yeah i read that too in a car magazine that a hollow bar is pretty much almost as stiff as a solid bar, i think they might have even given a reason and a formula or somethin to calculate it and stuff, but i dont remember exactly off the top of my head.

[eddiec]

i think it was sport compact car mag. if i could now remember the article i saw it in.....

[EnzoRWD]

well looks like i will be picking up the r32 rear bar. hopefully i wont get *too* much oversteer, im not going for drift setup...ill keep everyone posted and such....-Enzoedit: btw, its a 22mm bar, so thats about that biggest ive seen. could be good, could be out of control...

[Q45tech]

Everyone keeps talking bar diameters instead of real amount in pounds per inch that the bar as installed delivers. Easy to get confused as the bar shape and convolutions must be identical for bar size to even be close to meaningful.

A 1" right arm variation against oem 6" is very very significant ~~ 17%.

If you chose too large a bar, you can always substitute 1 of 4 urethane end link bushings with a rubber one [identical location on both sides].......to decrease the total and slow the engagement.......Some rubber is a good thing as this will isolate the bar for the first 1/2-1.0 inch of body roll making highway driving a lot more pleasureable.

A little rubber can turn a 40#/in bar into a #30.........when dealing with 24 mm [ 120# bars] start with full rubber and work your way up to urethane if you must..

[cosmo]

i think it was sport compact car mag. if i could now remember the article i saw it in.....

This month's issue, in the 350Z tech article, they use Hotchkis sway bars that are hollow

[Chingon]

i'll look it up...I'm kinda still doubtful.

[Chingon]

aha I found it:

"For a bonus, the Hotchkis bars are also hollow. It turns out that if you drill the middle out of a torsion bar you don't lose much in the way of stiffness, but you do lose a lot of weight. The massive 35mm (1 3/8-in.) Hotchkis front bar weighs just over 13 pounds. In its three positions, the front bar is 9-, 32-, or 63-percent stiffer than stock. The 24mm (15/16-in.) hollow rear bar is either 45-, 92-, or 146-percent stiffer than stock. Amazingly, we found perfect balance with both bars in their middle setting."

But why am I still sketpical?

[Chingon]

guess I'll still do it just for kicks...:P

[Chingon]

Ok, straight from hotchkis http://www.hotchkis.net/pdf_fi...D.pdf

Look at the beginning of page 5.

Like I was thinking and saying, a stock diameter tubular (hollow) vs a stock diameter bar-like anti-sway will result in the bar-like being stronger.

This changes however when the diameter changes, so a bigger diameter hollow may be just as good as a smaller diameter solid. The engineers do this by "fine tuning" the thickness of the tube walls.

[D Money]

project s13 has whitline sways i think

[Darius]

eddiec--

To answer your question about why a hollow bar maintains the same rigidity as a solid bar, it's a matter of engineering materials and mechanics. The outside of a cylindrical shaft resists torsion while the inner section does little in this respect. If the solid shaft is only in compression, the entire cross sectional area resists the force. Therefore, if you compare a hollow tube with a solid cylinder (of the same material and diameter) in compression, the solid shaft would be stronger.

Now when you are talking about torsion, as you move out from the center of the shaft, the lever arm for resistance increases linearly. Therefore, the area near the axis of the shaft does little in comparison to the outside area. So two bars of differing diameter with the same gauge metal and same material will differ in torsional rigidity. Clearly, the larger diameter will provide more resistance.

It's been about 5 years since I've looked at that stuff, so if anyone else can correct or add to what I've said, please do.

[clearview]

can you give me the web page for the foam

[Q45tech]

Roughly a typical [18-23 mm] hollow rear bar needs to be 0.5-0.8mm thicker than the same solid bar. Understand that the rear shocks only have a +- 3.4 " stroke and the way the bar is coupled to the mid point of lower suspension arm means the bar right angle arm moves [twists] on 3.4/{4} [the motion ratio] = +- 0.85 inches.

Hopefully you see that 4 rubber bushings on each end link could create lots of slop before the bar moves at all. If each bushing compressed 0.1" on both sides 4 x2=8 the rear bar would never twist at all.

Fine adjustments allow great changes in EFFECTIVE bar stiffness as translated to the wheel.