?

 

Hollow... stiffer

 

how on earth is a hollow bar stiffer than a solid bar?

for street car - it truly makes zero difference.

 

Hollow and solid are equally as stiff. A solid bar would be stronger than a hollow bar, but sway bars work on torrsional stiffness, aka twist. Technically, a hollow bar would perform the same as a solid bar in that case. Hollow would be better because of the weight savings.

I agree with z1 because the weight savings is so minor. You would only notice this minor of a weight savings in rotational mass.

 

if both are equal length and outside diameter= solid will be stiffer.

 

"Stiffness" is what is most important...all else being equal, hollow is better because it's lighter.

 

For bars of equal weight the hollow bar will be far stiffer. The majority of the deformation is near the outer edges of the bar and that is where you need the metal. (the same reason an I-Beam has almost all the metal on the tops and bottoms)

The metal near the center of a solid bar does very little for you.

However, hollow bars are more expensive to make and at some point the diameter gets too large for fittment. So bars above a certain stiffness usually end up solid so that they are not 2 inches in diameter or more.

Typically aftermarket bars are solid because they need to fit in the stock location and if they were hollow they would be significantly larger in diameter than the stock hollow bar.

 

throw different alloys into the mix.... or different heat treatments.... or....

not that I know anything about alloys or treatments. I don't think one can say a _ hollow bar is better or worse than a _ solid bar.

just my thoughts...

 

It really comes down to preference. There is no technical reason that one is better than the other.

Facts:
1. The diameter of the bar and the position of the attachment points are what determine the stiffness. Whether it is hollow or solid doesn't really matter.
2. A solid bar won't bend as easily as a hollow bar
3. A hollow bar is lighter than a solid bar.

Choose based on what you feel is most important.

I personally like the hollow, adjustable, Hotchkiss bars.

-D'oh!

 

If stiffness is the key issue....who makes the stiffest bars? I noticed tha Cusco's claim to be 177% stiffer than stock...that sounds kinda extreme...but can someone give me some insight. I'd also like to pick up some sways, but I am having trouble deciding which ones to marry up to my Tein Flex coil-covers.

 

Stiffer sways are not always the best solution. You really want to control body roll with suspension geometry and spring rate; not shock dampening or stiffer sway bars. Shock dampening should be just enough to control the spring in given conditions. Sway bars are valuable because they don't require insane suspension designs like F1 cars or super stiff springs, thus making the car affordable and streetable.

I rarely say it, but Superstreet's article for pushing the Z to 1G+ on the skid pad is an excellent read. But note how the car became slower through the salom.

 

The weight difference isn't very significant for a street car in comparing hollow to solid nor is the difference in rigidity from hollow to solid. Also, any performance data like slalom speed is a hint or indicator of how the car will perform, NOT of what car "handles" better. The Sentra SER Spec V out slaloms a 350Z as they both sit on the Nissan showroom floor and although it's a fun car to drive, I'd take the Z's underpinnings ANY day of the week for a track flogging. Lets assume both cars had equal power to weight ratio...the Z will feel and drive like a more serious performance car. Slower through the slalom may still mean the car is capale of better grip and higher entry speed to corners etc...a meaurement like slalom speed is indicative of tire grip, body roll and weight transfer. You can drastically reduce body roll and the car can corner more easily yet run through the slalom at a slightly slower speed since they are very tight turns and the cars weight is now transfered MUCH more quickly from corner to corner and less dramatically. The point is, while one change in the suspension may provide "less" performance in one test, it could provide more in another (as in lap times) and no track car will have the same setup from track to track. The bar you choose and the setup you choose for it (if it's adjustable) depends entirely on the other suspension components you have and how you like the car to feel.

 

gq - Cusco's marketing is a bit misleading in that regard. I can get the actual diameters tomorrow

Here are the real specs (taken from our site):

Cusco is Japan's largest aftermarket suspension tuning company, and we are the #1 Cusco dealer in the country. If you are looking for an affordable, easy to install handling upgrade, these swaybars are just the ticket. Front sway bar is 2 way adjustable (20% stiffer than stock and 37% stiffer than stock), rear sway bar is fixed (73% stiffer than stock). Fits all 2003-2004 350Z, G35 Coupe and Sedan. Free shipping with purchase of front and rear sway bars! usually ships in 1-3 days.

Andy - assuming both bars have "ears" that are the same thickness, your explanation still does not show why hollow would be, or could be, stiffer

adam