Rear sub-frame nuts.
 

I started on a rear sub-frame swap about a month ago, got it about 90% done then life got in the way, and havnt touched it since. I finally have time to finish the install, and I cant find the big nuts that goes to the front of the sub frame.

Anyone now what size they are so I can go buy some at a local auto/hardware store. sub

I don't know the thread and pitch still, but i did go down to the junk yard to pull one off another FC. Luck would have it, they didn't have any there...

So I started checking random Mazdas figuring that there would be the same bolt somewhere. Yupp, found them on a Miata for the front suspension and the 929 rear subframe mounts front and rear. Probley a few other cars too...

Machine shop can tell you what thread and pitch they are

I was just dismantling the sub frame on my parts rx7 a few days ago.
All I can tell you is, I remember the size being 21mm. Among other sizes, 17 and 14.

Cool that you found them off other mazdas.

You can measure them yourself, M12X1.25X25 = a bolt that is 12mm in diameter, has 1.25 mm per thread and is 25 mm long from the tip to the base of the head. Nuts only have the first two numbers (M12X1.25).

The nuts are M14x1.5