I'll try and give the cliffs notes of my situation

-Had a FM turbo B6 in my 1990. Threw a Supermiata organic 1.6 clutch in it with stock flywheel. No issues.
-Swapped B6 with BP6D & 6speed. Moved stock 1.6 flywheel and Supermiata clutch into new setup. Beat on it for 1500 miles with no issue
-On road trip to Glacier National Park, about 1000 miles into the trip, the gears become hard to engage. Clutch pedal becomes "gritty" and there is quite a bit of vibration transmitted during clutch-in. Attempting to shift into gear with the engine on makes the car move (while not entirely being in gear) We replace the master and slave & bleed. Issue persists.
-Limp car to dealership in one gear, they find the throwout bearing is lunched and swap it out.
-Car drives fine for 100 miles before the symptoms come back. Dealership finds another destroyed throwout bearing.
-Replace entire setup with Exedy 61-0122. Drive car 900 miles today with no issues. Clutch feels perfect. No adjustment was done aside from the clutch install.

I took a look at the parts that were pulled out and nothing is visibly wrong with the Supermiata clutch parts save that some of the springs appear to be loose. The only other observation I have regarding what happened is that there is quite a bit less rattle on decel after the Exedy was put in.

Ideas?

 

Is your clutch pedal adjusted so that it completely releases pressure from the TOB between shifts?

 

Just going to post the same thing. If the TO isn't released from the clutch after the pedal is let off, it's spinning the whole time. It's just not made for that.

 

you could try and get the upgraded one from flyinmiata. It's a monster. I had upgraded to their stage 2 clutch and it also destroyed the standard TO bearing. This was 7 years ago and no issues since.

 

^just make extra sure the HD release bearing from Flyin Miata isn't faulty. Mine was, but thankfully didn't grind all the way through the pressure plate, and Flyin Miata sent me replacements at no cost.

The release or throw out bearing should spin with a small amount of resistance, not free spinning, but it shouldn't be too difficult to spin.

 

+1 to clutch adjustment. Every clutch is different and might need different adjustment.