Jpr5690

iTrader: (13)

Not Tring To Knock Sam But Where Is Bmr, Umi Sphon, Slp, And Everybody Elses Hollow Bars

Mabye One Of These Companies Can Reply With A Answer To Why They Make 32mm Solid Chromoly Bars Instead Of 35mm Hollow Bars

wannafbody

iTrader: (2)

because hollow bars weigh less- if weight isn't a concern get the ST 35mm bar

02TransAm/Batmobile

iTrader: (32)

I've heard that hollow bars are just as strong as solid bars so why not make them hollow? Less material and less weight. Win, win combo.

Carlos01SS

iTrader: (4)

My understanding is that bottomline a solid swaybar will be stiffer...at the cost of additional weight.

A solid 35mm chromoly front sway will be stiffer than a hollow 35mm sway, and the hollow bar will be significantly lighter...less unsprung weight however, even if it's less than 10lbs, is still an advantage(albeit small advantage).

I opted for the hollow bar. I figure the lighter weight will offset the fact that even though the heavier bar is somewhat stiffer, the difference in weight savings will offset the stiffness, does that make any sense???

It did to me at the time!

wannafbody

iTrader: (2)

the weight is an issue for race cars but for a street car it probably doesn't matter unless you use a stopwatch everytime you drive somewhere

z28bryan

iTrader: (7)

Look up the Hotchkis and Addco bars. I believe those are also hollow. There's probably others The reason for making them is that they are lightweight. A 35mm hollow bar is not as stiff as a 35mm solid bar, but its pretty close. There's a cool little equation floating around here somewhere that tells you what a particular size hollow bar mimics in a solid bar. You would have to know the hollow diameter though.

Also, the Hotchkis I think is only sold in the 35mm front and 25mm rear pair. So you don't have a choice, you have to buy the huge rear bar. I'm not sure if the Addco bar is still sold or if there even was one.

Sam Strano

iTrader: (41)

Hotchkis bars are hollow too. Addco makes some for some cars, and they make mine for me, but I have the lock on the hollow F-body bars from them despite what the catalog sometimes shows since I came up with the idea, sizing and did the test fitting.

Solid bars are stiffer for the exact same size, but there isn't a huge difference. And note that the front bars are hollow from GM, not solid FWIW.

Why don't others do it? Don't know, and really don't care much. But I'd guess it's because you can kink the tubing and you have to bend a little more carefully.

gun5l1ng3r

The Z28 has a hollow bar, or do you mean SS/WS6?

Sam Strano

iTrader: (41)

Both..... 30mm and 32mm respecitvely, but both are hollow. Rears are solid.

Jpr5690

iTrader: (13)

id really like to hear fom sphon, umi and bmr.. this wasnt ment to knock anyone i am just wondering their reasoning for not makeing hollow bars may it be cost, practicality, or some other reason

JEB99TA

iTrader: (32)

Since Sam's bars are way more expensive, it could be the cost factor to make them, but, for me, it was worth the extra money to only be 3 lbs heavier than the stock bar vs. being 10 lbs heavier than the 32mm solid bar over the stock hollow bar as with the Spohn bar I ordered. From your sig, your car is a FAAAAAAR CRY from a streetcar.

Knowing you, John, you keep that stop watch busy on the street ... LOL!!! I like the direction you're going with your car.

Jpr5690

iTrader: (13)

Thnx... Jack

Chevy053

I was always under the impression that hollow bars size for size are stiffer. I remember back in college one of the questions in my roommates material science book was to calculate the resistance to torque of a hollow pipe and solid pipe of the same size and material.

The answer ended up being that the hollow one was stiffer because the outside of the bar is more efficient at resisting torque. Probably because it is further away from the center point. Of course that was an ideal situation with a straight pipe so maybe in the real world where the bar is bent in a bunch of different spots its different.

JEB99TA

iTrader: (32)

... sounds like it wasn't a chrome moly bar in your comparison ... they're not 'magic' but they are stronger size-for-size IMHO.

Jpr5690

iTrader: (13)

sam r u bars chromoly?

DONAIMIAN

iTrader: (18)

Eibach also makes hollow bars for our cars.

MeentSS02

iTrader: (11)

To the best of my knowledge, they are not...he doesn't like using chromoly in this application due to its brittle nature.

Jpr5690

iTrader: (13)

Intresting.. So Its Really 32 Solid Chromoly Vs 35 Mild Steel Hollow

Jpr5690

iTrader: (13)

If This Is True Then Theres More To Consider.. See Now Not Only Is It The Whole Diameter Debate But Also How Much Stronger Is Chromoly Than Mil Steel And Is This Enough To Warrent The Extra Weight.?

2002BlackSS

iTrader: (4)

Actually, there is much more to consider if you think about designing one. Fatigue strength, yield strength, and mass are all determined by material selection. Toss in bar geometry, cross sectional area, diameter(s) - depending on solid or hollow, manufacturing processes - both of bar stock and for shaping the bar, any treatments such as heat treating or even painting/powder coating, fittings design, cost of material and manufacture, etc.

In the end, the physics that govern the purpose of the bar don't really dictate that most people try to do any over analyzing of it. Anyone having any familiarity with steels knows that there's always a trade-off between hardness and fatigue and yield strength. Given a part that is under constantly variable torsional loading, it is usually preferred to have higher fatigue strength at the cost of rigidity - you'd rather have the bar give a little than break in two. That's why a favorite material for suspension components is mild steel.

As far as the difference in yield strength, this is usually negated by the design of the part. The use of a stronger material allows the use of less of it, so in this case, chromoly would allow for a lighter weight bar at the same strength of the mild steel bar. Again, this comes at a cost of durability and material cost.

Personally, I would agree with Sam (according to meent's post), that while chromoly has it's purpose, it's better to look to geometry to save weight than material.

Looking at geometry, a straight, round, hollow bar vs. a solid bar, all else being equal, will have about the same torsional resistance, which (torque) is really the main type of loading on a sway bar. Because of this, weight savings can be made by using a hollow bar, while still maintaining sufficient strength.

While I can't say what bar on the market is the best overall design, GM did more analyzation of the OEM bar than any of the aftermarket companies, and they settled on a hollow, mild steel bar. If you want a stiffer bar to enhance performance, one of the best ways to resist more torque is to increase the moment arm - thus the diameter of the bar.

My pick would be a larger diameter, hollow, mild steel bar. Mind you, the keys to enhancing the performance of the bar is the diameter and material. Hollow is for weight more than sway bar function, so if cost becomes a factor, keep this in mind.