InTrax Coil Springs?
 

Anyone have any experience or opinions on these? Friend found a set in his garage he bought years ago but never installed on his miata and they've been long since discontinued. Not sure of the spring rate or drop increment but he offered them to me pretty cheap. Looks like a set of new springs from them will run about $200.00.

from my experience, linear springs are pretty much all the same.

I've never been to the shop, but I imagine there aren't too many companies aside from eibach, h&r, swift, tein, and hypercoil making coil springs.

How cheap?
Tein S techs on ebay, (real ones) are cheap as heck so don't pay more for unknown when you can get a known spring rate with known drop.

He was talking like around $50.00.. I've seen junk Chinese springs on ebay for more than that, so I'm kinda thinking might as well give them a shot.. Just wanted to see if anyone has any dealings with them before I made the plunge.

M.net has a few OOOLD reviews saying they were good, random google search yields 0 miata related reviews, but a bunch of other crappy cars saying they're junk.. so I'm mixed opinions..

I take it these are not 2.5" linear coils...they're miata specific? If so, I'll first ask you why you're not doing ground controls, then stfu and say the VW crowd has good luck with them.

there are formulas to calculate the springs rates using the length width thickness etc etc.