I had heard that the later NB style control arms had some stronger internal bracing... I think I have an example of a NA arm that has collapsed.







It's tough to photograph, but the area just inboard of the swaybar mount is depressed in quite a bit - like the arm was trying to fold in half.

I do not recall seeing this bent when I installed my shocks/ coils... but I did spend a season on track with them - I did have a few offs, but nothing even close to major. The passenger side was not bent.

This arm was OE off a 90. I'm currently installing some '94 NA arms, but I think I'll be switching to '02 arms sooner rather than later.

 

Yep, bent from an off, they don't bend without help.

 

They dont bend there without help. You can bend and break those tabs off from running a BIG bar (like the 1.25 NB bar), on a stock spring car with hoosiers.

 

Sounds like that's what did it then.
At my last event @ Summit Point, I installed a 1.125" RB front bar. My springs were 375#, and I was running R-S3's. Before that, I was on the stock front sway.

I did drop the driver side wheel over the back of a kurb, that must have been it.

I've already prepped a new set of NA arms that are ready to go on the car... but I do have a Nb subframe/ arm setup here as well. Other than welding in the extra tab to make the late arm end-link mounts double shear, is there anything else I should look at?

 

No, it's not worth the weight penalty and time. Either go full tubular, or keep replacing them with stock pieces every 15 years.

To clear up Leafy's point, big bars DO NOT bend control arms, he was just refering to the end link tabs.

And I doubt that curb drop bent the arm. Mine took a curb smash. Have you compared it to the other side? Miata arms have some weird dips and curves in them.

 

Yes, thanks for clearing that up.

 

Got it.

Yeah, the other side is different, so are my 'new' pieces. This particular one is deflated just inboard of the swaybar mount.

It sounds like the verdict is: **** happens. Replace the arm and move on.