d 21mm diameter
t 2.6 thickness
L 32.374 bar length
R 8.5 lever arm length (if we use the 215.9 nick posted)
C 8.5 Lever lenght (if they are the same)
r 0 offset
G

what is R and C? I'll do the math



edit-whats G

 

I think R and C are equal because we don't know the angle of the moment arm. We have to assume for this that they the moment arm is at a right angle to the center section of the bar.

 

Couldn't you just use this link:
http://fromsteve.net/tech/Sway-Bar-Rate-Calculator

if the motion ration is .5 than the bar is roughly 530 lbs/in for the Miata bar if I plugged in the right numbers.

 

Umm, that seems rather high. The stock rear bar is lower than that according to this post.
https://www.s2ki.com/forums/index.php?showtopic=818884

The 06-07 is shown as 311lb/in

 

I screwed up, I forgot to put C (215.9 mm) in the formula. If the link you posted is just spring rate, than the Miata bar is 280 lb/in. Check my math since I screwed up once already. That is why I let Nick do the engineering and I just drive.

 

Shear modulus of the material.

11.6e6 psi for spring steel

 

That might have been easier. Using a 3/8" bolt in the swap bar meant that the Aurora 10mm end link would clunk. A 10mm bolt would not go through the SAE bar arm until I finally found metric drill bits.

Using an SAE end link on the lowed control arm might have worked, but I'm not that clever. I couldn't find a 25/64" bit unless I bought a 200+ piece set.

Nice thing about the Speedway is that new center sections come in many sizes and are dirt cheap.

 

I used the same equation from twohoos PDF file and was able to repeat his calculations for the '03 S2000 rear sway bar dimensions. He uses G = 1.12E7 psi which is what I used as well.

When leaving everything equal to the S2000 calculations except the diameter, thickness, and length I get 129 lbs/in? However, when I use the rate calculator on the web page pointed to by Andy I get the same answer if the motion ratio is set to 0.69. 0.69 was arrived at by entering the '03 S2000 rear bar info and adjusting the motion ratio until the answer matched the S2000 bar rate. This is somewhat of an independent check, but 130 lbs/in just seems too low.

Anyone do a search on the MX-5 bar for its rate? I will spend some time doing that as a check.

G = 1.12E+07
pi = 3.14159265

Bar Dimensions
d = 0.82677165 in
t = 0.1023622 in
R = 8.5 in
L = 32.374 in
r = 1.25 in
C = 8.9 in

 

What would be the regulation on jet coating some items? such as a header and a intake manifold?

I would think a header would be ok because a aftermarket header is legal and who says headers don't get coated. Although I'm iffy on the legal"ness" of a manifold.

 

Re:06 MX5 FSB -> S2K RSB
Guys, this bar is light, light, light compared to my '01 stock rear bar. I would be shocked if it would be in the same ballpark.

Autocross tomorrow... but it is a small sealed asphalt lot... and will be cool. But choosing my Toyos over the Kooks. (sorry Josh!) Should be interesting.

-Dave