Miata sway bar rates

[Marcus Miller]

Folks,

I'm trying to figure out effect rates of the various sway bar options for an ITA Miata;
Does anyone have the various rates for these bars, or know anyone who might have them?
27 mm 1.8 SM front bar
24 mm 1.6 SM front bar (adjustable)
19 mm 1.6 stock front bar
23 mm MSM stock front bar
12 mm 1.6 stock rear bar
11 mm 1.8 stock rear bar
15 mm SM rear bar (adjustable)

I figure I can't be the only one who ever looked for this, I'm jsut not talented enough to find it, and don't have time to measure it.
Thanks!
Marcus

[ddewhurst]

Call Eibach for the after market & Tim Buck of Mazda for the OEM bars.

[jerestahl]

It is extremely difficult to rate AR bars. The rate is a function of bar dia, arm length AND wheel rate and weight on the tire of the anchor wheel. Thus the rate for example on a Miata is different on the LF and the RF.

[quadzjr]

The rate is determined by bar diameter,metalurgy, etc.. The majority, atleast for simple mathamtics sake, happens along the longitudal part of the bar. Your wheel rate should be close to identical from left to right. Assuming you negate minsucle difference in mointng points from factory stampings from left to right. So if the right tire goes up 1" cuasing the sway bar to deflect .5" (assuming a 2:1 wheel rate. I have no idea what the miata is ) Why would the left side be any differnt?

[ddewhurst]

When I procure a bar I concern myself with the bar rate & the other stuff is secondary. Yes, one needs to understand the other stuff to conclude results.

[Colin Harmer]

There's loads of math out there that can solve this for you, I'll do one for you, but I won't run the entire matrix, it would take too long. As an ITA miata guy, I can tell you that Mike VanSteenburg has got the bar thing figured out, you should just order a set from him, but that's just my opinion.

If you want the bar rate, I will need the diameter and the length of the "lever arm" to give you the rate.

[Gary L]

I'm thinking you would also need (as a minimum) the center length... the part that is in torsion.

[modernbeat]

...As an ITA miata guy, I can tell you that Mike VanSteenburg has got the bar thing figured out, you should just order a set from him, but that's just my opinion.

If you want the bar rate, I will need the diameter and the length of the "lever arm" to give you the rate.

I've got one of Mike's bars. The softer of the two that he offers, the 0.188" wall thickness bar, not the 0.25" bar.

Here's the specs on it so you can do the math:

Outer diameter 31.75mm
Wall thickness 4.57mm
Bar length (to center of attachment point of arm) 822.3mm
Arm length (adjustable to these positions) 220mm, 235mm, 255mm, 280mm 300mm

I use a 54.8% motion ratio for the front bars with the stock arms. If the wheel travels one inch, the attachment point travels 0.548 inches.

Also, total weight for the bar, brackets, bushings, arms and endlinks was around 13 lbs 9 oz.