As the title implies, I like to think of this as the final boss of foamectomies.

I recently picked up an FL5 and love the stock seats. Reclinable, huge amounts of bolstering, very comfy padding and fabric. I wanted to recreate that in my miata as I dig the look of the stock cloth seats. I like to autocross at various spots, some up to 2.5 hours away. While I do have a bucket seat and bracket I can swap in, I need to be able to lazily bro lean while Im cruising down the highway. My solution, add a bunch of metal bolstering to the stock seats that sits under the foam and holds it rigid.

Here we have my frankenseat. The general idea was to extended the sides of the metal seat pan up into the foam for a rigid thigh bolster on either side. The bottom of the seat foam has a small flap the whole way around that sits outside the metal seat bucket. My thought was that I could continue to slice that groove further up into the foam, all the way to the top of the bolster and extend the metal of the seat bottom. A perfect solution would be to use some steel dowel like mazda did for the 94+ seats and weld it to the pan, extending it up even further into the bolster. I dont have a welder in my little apartment garage and wanted to be absolutely sure I wouldnt bend these bolsters.

I basically made 22 gauge metal plates that matched the profile of the foam bolster and backed them with 1/2" x 1/4" aluminum angle for an insanely rigid bolster. I sliced up into the foam bolstering with a bread knife trying to maintain a few mms of foam on the outside of the metal bolstering so as to minimize the amount of exposed metal. I bolted the aluminum angle and metal sheet to the bottom of the pan, after cutting the rolled lip of the seat pan out of the way where neccessary. Then riveted the upper end of the angle to the sheet metal. Boy are these bolsters stiff. The seat looks stock, is plenty comfortable, sits REAL deep with all the foam removed, and fits me like a glove. I am about a 30" waist but have a much larger hip measurement thanks to my more athletic days. For reference I need to buy special jeans with more room in the seat and thighs, so I'd say you can probably recreate this mod so long as near/below about a 34" waist. I have yet to drive with them but have an autocross event in a few weekends so I can report back. I expect them to be amazing.

 

Is that like the Paco seat braces? I have those but they mount under the seat and it does lift you up higher, yours looks like it would still retain the same seat bottom to floor measurement.

 

Very similar! But way cheaper if you're handy. And yes this does NOT bolt under the seat between the sliders like the paco ones so it will not raise you up. The bolsters are bolted horizontally into the sides of the metal pan. I also think the paco ones are meant to sit external to the seat foam/fabric? Mine sit underneath it all so you'd never know they're there unless you actually sit in the seat or try to wiggle the bolster. The pic with the seat bottom all buttoned up and covered with fabric is AFTER the install, they look very stock but perform much much better.

Like mentioned, I pulled a ton of foam out of both the top and bottom side of the butt pad. I sit very low now and plan to still cut out the rear seat humps and bolt the rear of the seat straight to the floor.