Hollow or Solid Sway Bar

[zbadone]

I have a 79 Z-28 with Hotchkis springs/Bilsteins and Nitto 555's. I have a 1 1/8" factory sway bar on it now. I am looking at either the hollow Hotchkis sway bar 1 3/8" or the Addco solid sway bar
1 3/8". Losing the weight would be nice, but would there be much difference in the cornering capabilities between the two bars? Any advice would be great.
Thanks

[86Cutlass383SR]

This has been discussed on another forum I'm on.

A lot of factors will depend on the final answer. Wall thickness, the length between the leverage part of the bar, etc. At only 1/4" larger, I'm not sure the hollow bar will be as strong. I'd also be curious as to how much less the hollow would weigh over the solid bar.

[silver69camaro]

Moving to 1.375" from 1.125" is a large increase in stiffness (provided the wall thickness is decent), and you'll cut the weight by about 40%.

More than likely the bar is about .188 in thickness.

[ArtosDracon]

I'm not that familiar with the most popular vehicle on here, but is the stock hollow? If so, I'd say it's a worthwhile upgrade, though the solid will be much stiffer.

[silver69camaro]

though the solid will be much stiffer.

In most cases, it wont be. Most of the bar's stiffness will come from, say, 1/3" of the outer material. The majority of the inner material is just along for the ride.

[Skip Fix]

FWIW on my daily driver street truck I swapped the factory solid bar for a slightly larger Hotchkiss hollow and could tell no difference between the two.

[zbadone]

Thanks for all the replys. I think I will be going with the Hotchkis bar.

[ArtosDracon]

In most cases, it wont be. Most of the bar's stiffness will come from, say, 1/3" of the outer material. The majority of the inner material is just along for the ride.

The problem being that most hollow bars are .188 wall and on a 1.25" if most of the stiffness comes from the outer most .66" you're not saving much removing the center. There can be little dispute that if you want the stiffer bar, given the same diameter, the solid will be the one to go with.

IMHO, you should figure out how much roll stiffness you want in your vehicle, then how much is provided without the swaybar and get the right bar to match what you need. Anything else is guessing at best.

[silver69camaro]

The problem being that most hollow bars are .188 wall and on a 1.25" if most of the stiffness comes from the outer most .66" you're not saving much removing the center. There can be little dispute that if you want the stiffer bar, given the same diameter, the solid will be the one to go with.

We are currently making the switch from solid to hollow bars - and we have about 20 different designs. They are consistantly 40%-50% lighter each time. Shaving 6lbs off a bar doesn't seem like much, but remember how far ahead from the COG it is - it reduces PMOI for better stability. These little benefits here and there add up!

79T/Aman, while arm flex is a valid point, it rarely proves to be an issue - hollow or not. There isn't that much force applied to the bar, or at least enough to worry about arm flex. Then again, in beam strength, the center of the bar is doing little of the work...again it's on the outside. The bars are typically made of heat treated 4000-series material, which makes them stiff (bending wise, not torsion).

Guys, remember OEMs have been using hollow bars for years...it's nothing new. If you do the design right, it's a no-brainer.

[IBDMANN]

will speed-tech be offering a hollow bar any time soon?

[JRouche]

In most cases, it wont be. Most of the bar's stiffness will come from, say, 1/3" of the outer material. The majority of the inner material is just along for the ride.

Yup!! A solid bar is mostly extra weight with no use. Thats why OEM went with a hollow bar. Its old tech but still needs to be talked about. Solid bars are a thing of the past. JR

[79T/Aman]

everyone ALWAYS forgets to count the lever arm portion of the bar, it flexes unlike the center section that twists, the hollow lever arm of the sway bar will negate any gains from the larger center section, furthermore the bending process needed to bend hollow tube shapes the sway bar like a crank putting a bending force on the ceter section of the bar instead of a twisting force, hollow bars are not worth the price to save 7-10 lbs and they take up more room causing clearance issues

[onechev]

going to a bar that much bigger is going to make the front a lot stiffer if weighs important then i would pay more and get a hollow bar. the hollow bars i have use did not seem to be as stiff as a solid bar same diameter.

[ArtosDracon]

I still use nascar style gun-drilled straight bars with billet arms on everything but my DD, and it's completely stock. There is something to be said for just using what works.

And really 6-8lbs, most of the guys I've seen that worry about saving 8 lbs on a sway bar look like they could afford to lose 40lbs before they got into the "healthy" weight range. Taking a big dump right before a race can shave a pound or two, that doesn't mean laxatives should start being standard racer equipment.

[onechev]

i see paying more for a drag car where less weigh results in quicker ets but how much weigh bais change will come from 6 pounds and what different result do you think it can give you on a pro touring
platform? cost vs benefit

[Skip Fix]

So how much weight does billet pulleys,hood hinges braided line etc add vs stamped steel factory pieces? And as the other guy said that Big Mac for lunch.

Heck even my mainly drag car ran the same with the solid 22lb front bar back on it!

[wmhjr]

So how much weight does billet pulleys,hood hinges braided line etc add vs stamped steel factory pieces? And as the other guy said that Big Mac for lunch.

Heck even my mainly drag car ran the same with the solid 22lb front bar back on it!

My billet pulleys and hinges weigh less than the stock OEM steel stuff. JFYI. Good question about braided line, but I suspect very little total weight difference - certainly less than 1lb in an entire car. They are likely offset by aluminum hose ends which are lighter than steel, but who knows.

[wmhjr]

A lot of people are missing the point here. A couple things - and I KNOW there are people on this site that are far more experienced and educated about these things than I.....

1) It makes absolutely zero difference what the maximum stress calculations, etc are concerning solid versus tubular. All that matters is whether or not the device is capable of supporting the maximum amount of stress IT WILL ACTUALLY EXPERIENCE IN A GIVEN APPLICATION. To summarize, you could have a sway bar that is strong and stiff enough to propel the Battleship Missouri through the Panama Canal, but it will be no more effective than one designed to support barely 100% of what the car "needs". Overkill is without value.

2) As it pertains to weight, people are forgetting the differences between weight and weight MOVEMENT and REDUCTION. Some examples:

Taking spring vs unsprung weight into consideration, I'd guess the sway bar is partially both. The center section is sprung, but the outboard areas in vicinity of the end links I suppose are sprung? That muddies the waters a bit. But in any case, reducing the same amount of weight so far outboard and forward in the vehicle will certainly have far greater affects than losing that amount of weight in your beer belly.

Beyond that, it's the weight MOVEMENT. In order to get around corners in a reasonable effective manner, we attempt to get proper weight distribution in terms of COG and balance, right? By reducing mass so far forward, we effectively move weight distribution. It's one reason why when I weighed my car recently, I was not upset that the car is still pretty heavy - roughly 3700lbs. That's because while the total weight was NOT reduced a huge amount during my build, the weight DISTRIBUTION was. Left to right the car is well balanced, and front to rear distribution was 50.6% front, 49.4% rear. Every little bit such as rear battery mounts, aluminum heads, tubular sway bar, helps. The stock 7/8" solid front bar probably weights 3x that of the Hellwig 1 1/4" tubular bar that's on there.

My take is that if your'e replacing the bar, not going tubular makes no sense. If you don't need to replace the bar, it's probably not a game changer.

[Norm Peterson]

1) It makes absolutely zero difference what the maximum stress calculations, etc are concerning solid versus tubular. All that matters is whether or not the device is capable of supporting the maximum amount of stress IT WILL ACTUALLY EXPERIENCE IN A GIVEN APPLICATION. To summarize, you could have a sway bar that is strong and stiff enough to propel the Battleship Missouri through the Panama Canal, but it will be no more effective than one designed to support barely 100% of what the car "needs". Overkill is without value.

Actually, what you want is what provides the balance that you seek. It is entirely possible for "overkill" to put you at a clear disadvantage. Using a drag race rear bar anywhere except on the drag strip is one example. At the other end of the car, I'm pretty sure that the bars used in the "big bar soft spring" circle track setups would be way too much for anything you'd drive on the street.

Numbers aren't magic solutions in and of themselves. But they do give you a way to put things in order or to get a feel for what a given change will generally do (without buying everything available and having to try it all).

90% of a solid bar's stiffness lies in the outer 22%, and 95% in the outer 26%. The tubular bars in those cases would weigh about 68% and 78% as much as a solid bar of the same OD. FWIW.

It's better when making a tubular bar to start from larger OD stock than you'd use for a solid bar, as long as you don't let the wall thickness get too thin trying to meet your stiffness target. Just as reference, Ford's OE bar for the S197 Mustang is 34mm OD, and the wall thickness is 15% of the OD (1.34 x 0.20 tube). A 1.375 x 0.25 adjustable bar is aftermarket-available. I think I've heard that 15% wall thickness guideline elsewhere as well.


Norm

[wmhjr]

Actually, what you want is what provides the balance that you seek.

This may well be the perfect summary. It's all about individual needs and the combination you're putting together. Wrong answer to concentrate on the sway bar and excluding the remainder of the suspension/chassis.

It is entirely possible for "overkill" to put you at a clear disadvantage.

Norm - agreed. I should clarify, I meant that in terms of "Strength" or the "ability to resist deflection/flex" overkill provides no value. In terms of "performance", too much may well be a bad thing.