I can confirm with 100% certainty that these are exactly the factors that made your engine sit lower than factory height.
Our measurements were taken using brand new OEM mounts and with the lower cup, as intended to be used by the factory.

Hey there, this is my first post. I'd like to add my experience with these mounts and throw in a question as well. I threw them on my stock 04 while prepping for its first track day and I have to say the NVH was CONSIDERABLE, even after over 500 miles and a handful of solid canyon runs. The shifting? AMAZING. The headaches they gave me? Not so much. It was particularly bad between 2.5k-3.1k RPM (so driving around town which is all I really do during quarantine). There could definitely be other factors involved but I haven't tracked them down yet. This is just what my experience has been. The quality of the mounts is exceptional and I'm still a huge fan of blackbird, but those mounts are coming off.

A brief side note: I ordered the street mounts but looking at the comparison photo between the street and competition bushing on the drop mounts, mine look like competition, not street. It's hard to tell with only one type in my hand and comparing it to pictures but that would explain a lot. Now onto my question.

Hopefully I don't get too much flack for not building it myself, but an amazing deal on a fully track prepped, 38k mile, 2001 stage 1 FM turbo miata, with all of the goodies (xidas included :D) popped up and I had to jump on it. The mounts are pretty well shot and need replacing though. Since my 04 is still pretty much stock and oh so comfortable, I'm switching back to oem mounts and want to throw the drop mounts on the turbo. The problem is I don't know if they'll fit. Can anyone with experience, direct or indirect, chime in on this?

-Darien

Can relate. At idle it was fine, but between taking off and a casual street gear change engine speed (3xxx rpm), the nvh was most prominent and guaranteed.

I too wondered if I had received competition mounts accidentally, but haven't chased it up yet since removing them from the car.

I’m glad I’m not the only one! I’m too busy at the moment to remove them myself so I had a shop do it today while I was working. I’m picking the car and mounts up in the next hour or so and can try and post pics of them then. The main difference between street and comp in the pictures was the diameter. I’ll see if I can get a good pic showing a measurement and maybe blackbird fabworx themselves can comment on which ones I have.

57mm, comp or street?
https://cimg7.ibsrv.net/gimg/www.mia...6b352132d0.jpg

Edit:

Seems like non chamfered edge style mount is comp

https://cimg8.ibsrv.net/gimg/www.mia...7657e655d5.png

https://cimg5.ibsrv.net/gimg/www.mia...03ae06800f.png

https://cimg7.ibsrv.net/gimg/www.mia...412a47510.jpeg
This is mine. The proportions just seem different than the street performance in the comparison picture. It’s probably just my imagination ¯\_(ツ)_/¯
https://cimg8.ibsrv.net/gimg/www.mia...a22b4481c.jpeg
Without the measuring tape you can see it’s pretty much identical. I wish I had experience with awr or innovative to have an nvh comparison between all three.

Confirming that the mounts that you received are indeed the Street Performance mounts that you ordered.
The NVH is a subjective matter, what some people would consider "too much" others consider "too soft" (yep, heard that too..).
The best advice I can give you is to hold on to your set, we will have replacement bushing inserts that are lower durometer soon and those may work for you better if you're interested.

Awesome thank you! Do you have an ETA?

Don't give up they will calm down with use. Keep in mind 500 miles is not the same as 500 miles of "working em in". I run comp mounts with mid grade bushings and the engine vibrations are minimal (but track car). In you shoes I would make sure the ears of the block mounts are not pinching to tight onto the side of the mounts. Maybe squeeze a washer in there to keep the sides of the bushings from rubbing up against the block mount too much. Spray some silicon on there to just to get things moving. The harder you drive it the sooner they will soften up. Great product! I love mine!

I've got the standard height street low NVH mounts. 2 years later, I'm still really struggling with the NVH.

It got very marginally better but it's still awful. I'm tempted to either

1. Void the poly mounts in the vertical axis, so the engine can still move with the vertical pitch and shaking force from an inline 4 but still have torsional stiffness (around the crank) for torque reaction
2. Change the poly bushes out for rubber (possibly an OEM car suspension bush?), since for a given stiffness at low frequency (shifting), it is less stiff at high frequency (vibration). Issue would be trying to find one stiff enough (and that fits, has anyone measured the low NVH bush size?) at low frequency....
3. Try the supermiata hybrid style of reverting to a Mazda competition mount on the exhaust side.

Has anyone else tried anything to reduce the NVH on these? I know they improve shifter location, but the NVH just ruins the car for me.

If you're concerned about NVH then forego the Supermiata hybrid style mounts as well. I have them and it makes the car pretty miserable at idle. I'm going back to dual mazda competition mounts.

I'm also looking to improve mine. I have the drop race mounts and they're just completely ridiculous (even for a track only car); solid mounts for all intents and purposes. I don't miss shifts anymore, but at the expense of my car rattling to pieces. I get comments warming up the Miata in the paddock from other racers about all the rattles and squeaks that drown out the engine and fairly loud exhaust. They've had no significant break in after 2 seasons. I push it out of the garage and start it in the driveway so my whole kitchen doesn't rattle to pieces, again from all the vibrating parts like the bumper covers, headlights, dash cover, hood, everything in the engine bay, etc... I watch the Spec Miatas fire up near me all quiet and think WTF have I done!?

I've been looking for off the shelf bushings with softer durometers to try swapping in. So far no luck. Most manufacturers selling bushings to size only have one hardness.
Looks like I have to cast my own bushings. https://grassrootsmotorsports.com/ar...hane-bushings/
US Composites sells 2 part mold urethanes: Molding Rubbers
You can make molds out of the current bushings with some plaster of paris. I'm going to start with 60A durometer and keep going until I'm satisfied. Balance shifter staying in position with the car not rattling to pieces.

I had solid aluminum mounts at one point and trust me that was unbelievably bad. Could not see out of the mirrors bad. With the current mounts and mid grade bushings (80?) it idles nice and smooth at 1000ish RPM's, mirrors remain clear. There's one bad portion early on the RPM band where it can be tough but it's a very narrow section that passes quickly. I also run welded PPF (double stacked and welded) so I'd expect mine to be even worse but again it's very livable by track car standards. It's possible that we just have different tolerances for vibration but I suspect there's something else going on with you and Tran. Make sure the ears of the mount are not clamping the entire face of the bushing tuning it into a solid mount. Spread the ears and jam some washers in there to contact the sleeve inside the bushing. Lube the faces of the bushing too. You can also try and order the larger street bushings/chassis mounts and see if that changes things. Good luck bud I know this can be frustrating.

I switched one side to a Mazda comp mount and it was significantly better. It went from unbearable to "eh I can live with this if I don't daily drive it"

Totally agree you're probably more tolerant of NVH than myself. My ass and ears are quite sensitive to seemingly imperceptible noises and vibrations after a decade of OEM engine development.

I think you're onto something with the bushing ears.
I pulled the drivers side mount off this morning to have a look see. I've spent my July racing budget (and then some) buying the billet MiataHubs and patching it back together after LF hub failure at Gingerman in June, so the car is idle until the end of August.

https://cimg6.ibsrv.net/gimg/www.mia...94dcd02108.jpg
Measured individually, the bushings are 0.4mm shorter than the steel tube they slide into. However, they are being compressed during install and are elongating. They are touching each other and causing one bushing not to fully seat.

https://cimg7.ibsrv.net/gimg/www.mia...3d6027e41d.jpg
The bushings are 0.4mm proud of the steel sleeve.

https://cimg9.ibsrv.net/gimg/www.mia...38fe43880e.jpg
The bushings are an interference fit with the ears of the engine side mount without even installing the inner sleeve. This is causing energy from the engine to short circuit through the ears of the bushings. Energy should be transferred from then engine side steel mount to the steel sleeve and then through the center of the bushing out to the chassis side mount. Instead it's going from the ears of the steel engine side mount through the thin bushing ears.

I've had this issue before with poly suspension bushings, where they are wider than the inner sleeve. The entire bushing face is being compressed in the housing and causes extremely high friction. Going to sand the bushings until there is about 1mm of the sleeve protruding and retest.
They should look more like this when installed:
https://cimg7.ibsrv.net/gimg/www.mia...c64a4bf623.png
Enough clearance that they're not being compressed by the housing, but not too much that there's excessive slop.

Yeah that's what I was talking about! You did a MUCH better job articulating it though. I had similar issues using poly in Lower Control Arms on my 911. I ended up machining down the steel insert instead since I had a lot of material to work with. Based on what I am seeing I would take a cartridge roll and sand the insides of the mount to remove the powder coating, grease the crap out of it (never seize seems to work better and takes up less space than the sticky clear shit), that should stop rust and achieve the compliance needed. Good luck bud!

Please share the results of the test. I have the Street drop mounts with ~300 miles on them. So far the entire car resonates, the steering wheel shakes about half an inch, and I still get 2-5 shifts. The front end is seam welded, the engine has monster cams, and the idle isn't perfect, but still. I'm hoping something is wrong

I'm interested myself. Always thought I had more vibration than I should, but I just chalked it up to a tired chassis and BP life.

Update:
I sanded each bushing about 0.25mm on the outer face, greased all of the surfaces, and threw them back on the car. They actually rotate now with the main bolt torqued to 90 ft-lbs. When I initially installed them I remember having to torque the main pinch bolt on the car because I could not rotate them to the required angle otherwise. Definite improvement in NVH. It's still pretty harsh, but was a worthwhile improvement.

I was looking at the Innovative mounts and noticed this clearance is what they claim reduces NVH. Their bushings are tapered so that they don't even touch the mounts except through the sleeve in the middle. At some point I'm going to go back in and sand a taper in the bushings to replicate this. I found a belt sander works best. They will turn into a messy goo if you try to grind them.
https://cimg0.ibsrv.net/gimg/www.mia...b2365b1b3d.png

I also found that there was significant axial preload of the bushing. I had some 0.2mm shims of the correct size for crush tube in the garage, but only 7 of them so this side got 4 shims and the other side got 3 since the preload didn't look quite as severe. I will post back with how I get on with this. If the vibration is still bad, I may drill the bush above and below the crush tube to let the engine pitch and shake in Z without transferring it directly.

For info, this has been run for 2 years, probably 20 racetrack hours and 5000 (very vibratey!) street miles.

https://cimg5.ibsrv.net/gimg/www.mia...b1a39e0b00.png