daigo

Does anyone know, or can tell me where to find the rate of the 951/968 M030 bars?

Thanks,

smlporsche

What do you mean by "rate"?

Joe Weinstein

A sway bar is a spring, and it's spring rate is the measure of resistance to torsion. That
depends primarily on the diameter of the bar and the length of the bar. If we assume that
all bars you'll be considering are the same length, the diameter is the single most important
comparator. Some fancier bars may be hollowed, slightly lowering their spring rate for a
given diameter. I am also assuming that you will be using the same moment arm; the
length of the arm at each end, from the central axis of the bar to the hole where the
drop link is attached. The resistance to torsion will rise as this length shortens.
Oh, and some people don't know how much they can adjust their adjustable bars!
If your bar has three holes in each arm, you have *5* different settings, not 3. Some
folks think the attachments have to match side-to-side, but they don't! The resistance
is simply the sum of the resistances to motion at each end, so the settings are 1-1,
1-2, 2-2, 3-2, and 3-3.
So to reprise the original question, the single comparator you need for a given car
is the bar diameter.
Joe Weinstein

SundayDriver

This kind of info does not tend to be floating around. Do you want it for input into simulation software, as that is the most common use for those specs? If so, you might contact the software author (guys like Wm Mitchell are a wealth of knowledge and may well have this data). If for other purpose, I am curious what you are doing with the torsion spec.

APKhaos

The standard spec for Porsche sway bars is their thickness. While its true that the thicker the bar the higher its spring rate, its the bar diameter that is quoted rather than its effective spring rate.

If you happen to know the matrial specs and diameter for a given bar, and the lever arm dimensions for adjustable bars, then the spring rate can be calculated, but AFAIK its not generally published [or known??].

333pg333

That's interesting as I've never heard of the sways referred to in a rate sense. However if you think about it they're acting in a similar role to a torsion bar. So does this mean that when we're calculating our spring rates overall that we have to take into account the sway bars?

daigo

I really appreciate everyone's input on what is meant by the "rate".
I am very familiar with sway bar rate. Most manufactures measure how many lbs it takes to twist the bar 5%. Yes, there are simple formulas to give you a rough idea. The M030 bar has too many variations to simply guess what the rate is. I just would like to know where our car is now to help calculate where we want to go.
So, if anyone knows, I would be grateful.

Thanks

chris walrod

You do if your are calculating wheel rate, total effective spring rate at the wheel.

daigo

He Patrick,
Not really, as they have different functions. Sway bars are only active in roll. It used to be commonly thought of that you set your car up as closely as you can with the springs, then use the bars to "tune". It can however get much more complex than that.

Mark,
Its for tuning purposes. We'd like to know where we are, so that when we make changes to the bar (design) we're not guessing. Yes, we do use software although I've yet to plug in all the points.

SundayDriver

If you REALLY want to know and can't find the data, you could measure it. Clamp the bar on a bench rig - restrain one end. Then hang a weight on the other end (probably a very heavy weigh) and measure the deflection angle. Prolly more work than it is worth, but it can be done.

Heck, while you are at it, do that to the whole car and measure the chassis stiffness.

wlittleman

If you want, post your bar diameter, wall thickness (if applicable), bar length, and moment arm length to each hole, and I'll calculate the #/in rate for you.