OK, so the plan is to use Corbeau Forza's with either the Corbeau sliders, or just a couple of thick pieces of steel bent to match the factory seat holes, then bolt the seats to those pieces of steel.
Obviously the shoulder harnesses go back to the Hard Core roll bar, but what is best place to mount the other three belts? I purchased a used set of Simpson 5pt harnesses with a cam lock.
From my understanding the sub belt needs to be mounted through the floor, toward the back of seating area..............it seems dead center in the seat also puts right about where we just got through mounting the FM Frame rail reinforcement and butterfly brace.
What's the best way to get everything mounted safely and properly?
Also, what about the lap belts? Can I use the factory location for the inside lap belt? Go through the floor toward the door jamb for the outside lap belt?
Also, I'm considering selling the Simpson harnesses and going with the Schroth FIA approved 4pt harnesses, since I will still be using the car on the street during nice weather.
What year Miata? Does the factory belt receiver mount to the trans tunnel or the seat?
On my 90 I used the factory mounting points for the lap belts, I just put some eye bolts in the holes (the threads were the same). I imagine that if you don't have the trans tunnel mounted receiver you could drill a hole and use a backing plate.
I haven't put in the sub belt yet but I imagine you could use one of the bolts from the FM frame rail reinforcement if it is in the right location.
Edit: I used these eyebolts, they thread right in instead of the factory bolts for the lap belts.
http://www.racerpartswholesale.com/product/Sabelt716IncheEyebolt/HarnessMountingHardwareAccessories
You can use the factory mounting points for the lap belts. On the NA, there's a threaded hole on the transmission tunnel even if the belt was attached to the seat. NB is a bit more of a hassle. Seat belt bolts must have some sort of federal mandate, as they're actually SAE threads and the eyebolts that (probably) came with your harnesses will screw in.
For the sub belt, there's a little access panel at the base of the rear bulkhead. It's glued down with seam sealer. Pop it out and you have about four layers of steel to drill through and use as a mount. You're right, you're right in the middle of the frame rail. Glue the panel back into place and you're golden.
I just realized that "you're golden" probably identifies me as a Canadian of a certain age, I think it's from a been commercial...
Keith wrote:
For the sub belt, there's a little access panel at the base of the rear bulkhead. It's glued down with seam sealer. Pop it out and you have about four layers of steel to drill through and use as a mount. You're right, you're right in the middle of the frame rail. Glue the panel back into place and you're golden.
Do you have to use a backing plate with it mounted there?
Just so I read that right...you bolt it to the frame rail under the access panel and have the belt coming out of the hole where the cover was?
edit: Now that I look at it...you mount the belt to the floor at the rear of the access panel and just use the access to bolt it in?
EvanB, yeah mine is a '90 as well.
Keith wrote:
You can use the factory mounting points for the lap belts. On the NA, there's a threaded hole on the transmission tunnel even if the belt was attached to the seat. NB is a bit more of a hassle. Seat belt bolts must have some sort of federal mandate, as they're actually SAE threads and the eyebolts that (probably) came with your harnesses will screw in.
For the sub belt, there's a little access panel at the base of the rear bulkhead. It's glued down with seam sealer. Pop it out and you have about four layers of steel to drill through and use as a mount. You're right, you're right in the middle of the frame rail. Glue the panel back into place and you're golden.
I just realized that "you're golden" probably identifies me as a Canadian of a certain age, I think it's from a been commercial...
Hopefully that picture will work when I get home, or I could go out into the garage. 
That makes me happy to know it's a simple solution. I was under the impression that:
a. Using the stock mounting points for the lap belt may or may not pass Tech.
b. That the lap belts/sub belt all needed to be mounted through the floor to pass tech.
I know at my local track it will likely pass, they will let you run HPDE's in convertibles with no roll bar if you want to. But I want to make sure going to other tracks with a more stringent tech process, that it will pass.
Keith, when you guys use the stock mounting point for the lap belts, are you putting backing plates/nuts on the other side of the eye bolt?
Drill a hole in the floor and use the access panel to put in a nut. There are about four layers of steel there, you can decide if you want a backing plate or not on that one.
Extra backing plates for the lap belt holes? They're OE engineered into the structure of the car and crash tested, I'd be amazed if a tech inspector would fail them as being inappropriate. But you could put backing plates on the transmission side if you wanted. The outer side is not accessible from the back if I recall correctly.
See the two white bolt heads to each side of the hole? Those are from a set of FM frame rails.
^So, if I'm understanding correctly, (I can see the pic now, weird), that is the "top" of the framerail, so just drill a hole through that but not through the framerail reinforcement and be good?
Correct. You're just drilling through the floor, not the bottom of the frame rail.
I suspect it'll be a lot more clear when you look at it.
Ahhhhhh!
I get it now, I now see the hole drilled between the two most aft Framerail bolts, so put the eyebolt for the sub belt there.
Even though you worded it that way, it wasn't sticking out to me first time through. Derp.
I used a 2x2x1/4" backing plate because my belts wanted the anti sub a little farther forward, but if I were doing it again, I'd go the access panel route. Also, for mine there wasn't room for an eye bolt so that may be an issue (or maybe not with aftermarket sliders). And Keith, I don't know if that marks you as Canadian...or just of a certain age (like me). See you at FM summer camp!
Well, I knew what hole I'd drilled.
^What about mounting a 6 point? I'm going to have to buy new harnesses and the Schroth Clubman's seem like a great deal.
That's more of a challenge. Some people attach the two points to the seat slider bolts, retapping the hole to an SAE thread and using eye bolts. The problem is finding the seat that will work with them.
z31maniac wrote:
^What about mounting a 6 point? I'm going to have to buy new harnesses and the Schroth Clubman's seem like a great deal.
I followed Schroth's instructions and recommended angles when mounting my 6 point harness. Basically drilled through the sheet metal on either side of the frame rail and used the backing plates and eyebolts like so:
eyebolts:
http://www.saferacer.com/g-force-eye-bolt-20mm.html?productid=882
backing plates:
http://www.saferacer.com/g-force-gf100-mounting-back-up-plate.html?productid=875
Hi I know this is an old post but I'm looking at mounting a sub belt in my nb in the same place. The mounting plate I've got is slightly too big to go down the back of the access panel. They will go in front of it however, so can I get away with mounting an eye bolt in front of the panel or will this cause problems? Any help is greatly appreciated.
There's a lot less metal there, I'd rather have a slightly smaller backing plate and a lot more car under the bolt.
Yes I say your golden all the time,yes it was a beer commercial.....no I don't remember it.
