How To: RX8 seats into FB
 

OK rotorheads - a detailed account of how I adapted RX8 seats into my 1980 RX7 SA. I know this will be valid info for any FBs, and I understand FCs also have the FB seat mounting pattern, but confirm this yourself.

Basically, RX8 seats are the same size and shape as the 7, but the mounting brackets are totally different, not the least of which the -8 brackets mount points make the seat sit way too high in a -7. A sample pix attached show the RX8 bracketry, which is complex to say the least. In contrast, the -7 seat brackets are about as simple a design as you could want, so why screw with simplicity? To me the obvious course was: attach the -7 brackets to the -8 seat rails.

My approach includes completely disassembling the RX8 seat to have the adapters welded on. I had a shop do this and there was NO way I was going to risk the seat cushions getting damaged. So I have gone into some detail about disassembling the seat. In a nutshell, what I did was shave off the RX-8 brackets off the RX8 seat rails and weld an adapter plate to the bottom of each rail, then welded the -7 brackets - at the correct spacing - onto the adapter plates. This means you still have complete slide adjustment of the RX8 seat on it own rails. (And since rails and frame are assembled as a unit, there is no option of removing the rails from the RX8 frame anyway). See the diagram of the basic layout.
NOTE: while I include measurements, I strongly urge you to DOUBLE check these yourself!! If you intend to farm the welding out, you will want a very accurate drawing of just what you want them to do - or they WILL screw it up!
Okee-doke.
Lets get going:

RX8 Seat Disassembly: (note this is the BASE, none-powered seat type)
I recommend that some steps be photographed so you remember how things re-attach later!
(This is for the DRIVER seat, but most instructions apply to the passenger side too)
1) remove (cut) the various underseat wire harnesses and the seat belt assy. This will NOT work with your -7 belt.

2) 3 of the 4 RX8 rails have plastic end caps on them. These need to be removed unless you want the welding to do it for you ;). Reattach on seat reassembling.

3) Inner (transmission side) seat frame plastic trim panel. These are 2 piece, sandwiched together. There is one small phillips screw, the rest being held together by the damndest plastic clips I have ever run into. There are about 5 of these little bastids and I cannot honestly tell you the best method of detaching them. I tried using a small flat-blade screwdriver and finally I just gritted my teeth and pulled the 2 halves apart! NOTE you cannot fully remove the INNER halves until the seat cushions are removed

4) Outer (door-side) trim panels. The seat tilt lever cover comes off first. More or less a press-fit onto the shaft. For the Driver’s seat you also have a lever for height-adjustment. The outer cover must first be pried off the center, round part of the cover and then the whole cover slides FORWARD off the adjustment arm. It looks like the INside of the cover on the arm portion comes off - IT DOESN’T. It stays on the arm.
The outer frame cover is held by TWO phillips as well as TWO push-in clips, and the usual @#$% clips I described above. You cannot see the two push-in style clips, they are inside the panel and plug directly into the frame, but a firm tug seems to pull these out clean. They are towards the front of the seat and if you can reach up under the rail on the INside of the frame, you should get an idea where they are so you can apply pulling pressure right near them and not stress the panel.
NOTE: all these trim pieces have the PART NUMBER inside them, so if you really bugger one up, you can easily (though I doubt cheaply!) replace them.

5) Seat back:
Note the hand zippers on each side of the rear. undo these. You’ll see that the rear fabric panel is attached to the FRONT panel with an interlocking clip on each panel that runs the width of the rear bottom. These separate easily BUT NOTE HOW THEY CONNECT! or you’ll be scratching your head later trying to figure it out.
With the fabric panels disconnected you can flip the rear panel up to the headrest, out of the way. Now the back itself. Cut the zip tie that holds the 2 horizontal bars (one is attached to the seat back, one is the seat frame cross-rail) together inside the bottom of the seat back. The back is held on by 2 14mm nuts on each side. Just lift the side panels and padding. Its a tight fit so I recommend a 14mm geared box wrench as the best tool.
Then feed the front panel flap under the horizontal frame rail. The seat back is free.

6) Seat Bottom: 4 12mm bolts.

7) Inner rail trim panels can now be removed

8) the REAR of the seat frames are now “free” from each side and the horizontal bar will just fall out because the rear rails aren’t bound together. I used zip ties daisy-chained together to hold the rear of the frames. Also, you have now exposed a LOT of gears and springs that require lubrication to operate for the life of the seat. If these mechanized areas of the rails are not protected, you will have a nightmare of metal shavings and grit all over them from the bracket-cutting and welding process. I wrapped them in zip-lock freezer bags and heavy packing tape.

RX-7 rails:
This is important. What you want to use is the LOWER part of the rail assemblies to be welded to the RX8 seats. As the RX7 rails are configured after you unbolt them from your old SA/FB seats, they are comprised of TWO components crimped together, the upper assy (part that bolts to the RX7 seat) and the LOWER assy, the part that bolts to the FLOOR. So the upper assy must be cut off the lower assy. Your weld shop can do it in seconds BUT THEY NEED TO ABSOLUTELY KNOW WHICH ONE CAN BE CUT. Ask me how I know this.... ;p This is especially important with the passenger INNER rail because it is unique and its configuration can be confusing. I marked an “X” on the sections to be CUT when I took them to the welder (and they still messed one up!).
Once disassembled, I took the bottom rails to a shop to get them beadblasted clean, since I painted the whole adapter assembly once everything was welded together. You will NEVER get them clean enough to paint once they have been welded to the RX8 frame. In hindsite I would have then (after the beadblast) painted the INSIDES of the RX7 rails because these are all but inaccessible once welded to the RX8 frame. Bear in mind with any painting you do prior to welding, contact areas of paint will be cooked off with the welding. Plus, those parts of the RX7 rails that mate to the adapter shouldn’t have paint on them anyway for a clean weld.
Final Note: I suggest you get the driver seat welding job done at a separate TIME from the passenger side - why? so there is no chance the welder will MIX UP THE RX7 RAILS as to which set goes to which seat!!!!!

CUTTING THE RX8 FRAME:
In addition to the plastic wrap of the lubed parts, I wrapped the entire frame in that 2” or 3”-wide blue paint masking tape so it wouldn’t get all chipped and scratched up in the shop. Just don't mask too close down tot he weld areas, since the baked tape is tough to remove...
My first thought was to have the weld shop grind off the various brackets right down FLUSH to the bottoms of the RX8 rails. Logic said this would give me a nice flat platform to mount the adapter plate to. The weld shop pointed out that grinding is (a) very messy and (b) not an exact science. The easier thing was CUT off the brackets at THEIR base, leaving the flat base still attached to the rail. To go the extra step of grinding the thin base down to the rail would generate a LOT of fine grit (that would get into all the nice, lubed gears of the frame’s adjustment systems), and likely it would mean grinding thru the bracket base AND thru the rail underneath at some points (see (b) above). And there is enough surface area of bracket bases to mount the adapter plate on without going right down to the rail. And its cheaper ‘cause its less work...

THE ADAPTER PLATE:
Bone simple. Flat piece of 1/4” steel on each rail.
NOTE: the RX8 rails are about 1” wider apart than the RX7. I mounted the INNER (transmission-side) rail DIRECTLY under the RX8 rail, doing the width correction on the OUTSIDE rail (door side)! Why? Because centering the RX7 rails relative to the RX8 rails forces the INNER RX8 rail too close (like INto the carpet) against the TX tunnel. Again, ask me how I found this out....
I was concerned this would throw the seat center off 1” relative to the steering wheel while I am sitting; reality: no noticeable difference!

Length: The adapters need only to be as long as the RX7 rail: 13+ inches.
Width: The INNER rail can be 1+” wide (enough to accommodate the width of the RX7 rail), while the OUTER adapter needs to be 2+” wide, since the RX7 rail is offset to the INSIDE of the RX8 rail. Follow? (see photos)
NOTE: the adapter plates -and then the RX7 rails - should be welded to the FORWARD ends of the RX8 rails (unless your really height-challenged) so you have maximum legroom!

THE WELDING:
-Measurements:
THE critical measurement is the SIDE-to-SIDE SPACE BETWEEN THE HOLES of the RX7 Rails (ie distance across, between the front rails holes, ditto the rear). The BEST place to measure this distance (15 3/8” but DON’T take my word for it!) is the MOUNTING HOLES on the FLOOR of the RX7!!!!!!! Hole center-to-hole center
-Again, make sure the welder is clear about which RX7 rails go where, and in the case of the passenger INNER rail, which end is FRONT!!!!!! Simple clear diagrams are a must unless you are going to be there!
I state the obvious but: the welder needs to understand that the position of the RX7 rail pairs need to match, side-to-side (ie the leading edges are in the same forward position relative to each other). This is trickier with the passenger seat because of its funky front mount point!!
-when you take the RX8 frame to the shop, MAKE SURE THE RX8 SEAT RAILS ARE POSITIONED ALL THE WAY TO THE FRONT OF THE FRAME!! (This would be the position for maximum leg room) Why? Because in the welding process, the heat will likely cook off some/all of the lube in the rail channels, or worse even bind up the slides a bit. When I got mine back there was only about 3” of slide motion in the rails. They would NOT slide all the way up to the original “short-legs” position. No problem for 6 foot me. (I did try to re-lube them, but it’s pretty well sealed up and you can only access the very front and back of the slide channels.)

Back from the shop? Now is the time to mount the empty frame into the RX7 to check for fit. Because the rails are tied together in so flimsy a fashion, don’t try to hard to slide them back and forth on the rails. Too much play. You may note at this point that it will be a bit of a grunt to get at the rear mount bolts...

Paint Frame and rails (adapter and exposed welds will rust otherwise). I used hand-applied POR15 gloss black followed by a spray of Black gloss metal paint.

Re-assemble seat. You took pictures, right? :)

Enjoy...

How To: RX8 Seats addenum
 

.....And one more shot of the naked RX8 frame with adapters and RX7 rails mounted prior to seat re-assembly...
Stu Aull
80GS
Alaska

Nice job on the write-up. :bigthumb: Looks real nice.

HOW To: RX-8 seats
 

Okaaaaa-
now with the actual pic!
:)
Stu Aull
80GS
Alaska

Nice write-up! Thanks for sharing the details. The photos are excellent, too.

Did you notice if the seat was lower than stock? I am curious as the drivers side seat does have the up/down height adjustment; whereas the passenger side doesn't. Although I have yet to mount the passenger side RX8 seat in my first gen project, I've noticed that it does sit higher; making the seat-back headrest noticeably higher and closer to the headliner. (I just have my passenger seat sitting in the car for now; not mounted with any fasteners.) My concern is that we'll have to cut away more of the underrails to get the passenger to sit at the same height as the driver's side. Please post your findings as you move forward on your project.

Looking good, Stu. What made you go with -8 seats over the more common TII or Miata swaps?

this needs to be added to the FAQ

Say Stu, do those seats have the heaters in them? Might need em up there in Alaska. Nice very useful write up, thanks!

ray

I was thinking of doing this exact thing, thanks so much for that write up. Also its good to see what they will look like in the 7 and now ill deffinatly have to try this. Thanks again. :bigthumb:

Nice job
 

Looks sweat, I've always wanted to put RX-8 seats in my first gen,
Great job on the write up ,,, GREAT JOB :bigthumb:

Thanks guys- nice to be able to give back to the community...
Chuck- the RX8 seats are slightly taller, even after I chopped all the crap off the RX8 rails; nothing a couple more notches in the recliner doesn't solve BUT if you jack up the Drivers seat (it has a height adjustment), my bald spot is brushing the sunroof glass. Could NOT raise this seat in a non-sunroof RX! Don't think the passenger side will be a problem for you.
Hammmy, as soon as I saw the Rotor-cut-outs in the headrest, I knew I had to have them!
$350 for the pair - brand new - on ebay, helped! :)
Stu Aull
80GS
Alaska

have you installed the pasenger seat yet ?

Very nice and 350 bucks new is a steal!! Can't wait till I have the money to do a 8 seat swap like this!

I love my RX-8 seats. Very comfortable. Just gotta get off my ass and install the passenger seat.

https://www.rx7club.com/attachment.p...hmentid=152003

Oooh, and here's my custom power window and heated seat switch panel
https://www.rx7club.com/attachment.p...hmentid=152072

Nice leather seats! I installed the grey cloth RX8 seats. The passenger seat required some 80/20 aluminum T-slot machinery hardware for my installation. I'm sure someone can come up with a different mount, too. One of these days I'll have to put my CAD skills on display and show how I approached it. You can see the T-slot hardware that I used on my cardomain page (click on sig).

That looks great... my only problem is that you puriest would hackel me for having a rotor shape (the one in the seat) in my V8 FB. But if I can find a pair I'll take my chances.

Heated seats in a rx7 is like having A/C on a snowmobile. WTF?

Nice write up. The second most favorite part of my rx8 was the seats.

I miss that car.

Me too

this is a must know page...was looking into some leather black/red rx-8 buckets...this will definitly help!

That makes no sense. What's wrong with heated seats on an RX-7?

it still hasn't stated how to install the passenger seat...

that's because the way I mounted it jacks the seat up 2", meaning only a REALLY short person will be comfy in it. I need to rethink the bracket design. So I didn't post it since I don't think I am doing anyone any favors...
Anyone else have a proper install method for the passenger seat??
Stu Aull
80GS
RX8 seats
Alaska

Whats wrong with heated seats in a RX7? Kim have you driven yours for long? The exhausts heats yours seats up real nice during the winter, our cars have built in heaters from the factory.

In the summer after a long day in a parking lot its like driving an oven, but this is off topic. Nice job on the seats and write up I might look in to that

Its like driving in an oven year round here, so be glad you all get some kind of winter. I have only seen snow a hand full of times.

you see the mmo under the leather seats he knows whats up mmo all the way

so i can't install them in a not sunroofed fb? :squint:

Sure you could!
Unless these people are driving their cars around without the sunroof in them all the time, what difference would it make?
I think the only reference to the sunroof was that the seat couldnt be raised in a non-sunroof FB. Now Im not sure if I understand this completely, but I assume the only way to raise it is with the sunroof open?
But do you really need to raise it? Im sure if you kept the seat in the lowest position it wouldnt give you any trouble, and comparing a non-sunroof car to one with a sunroof thats closed my guess is that the non-sunroof car would have more headroom.
Now this is all speculation, but I cant see the sunroof car making any difference if the sunroof isnt open.

Id like to hear the opinion of people that are using the RX-8 seats though.

I forgot to mention, if the car has a glass sunroof installed that could make the difference. Since the Glass sunroof is only like 1/4" thick, you gain around 1.5" of headroom compared to the where the solid sunroof used to dip down. This might mean a small amount more clearance, but we really arent talking much.

If its coming down to mere inches for these seats to fit, I would say they arent worth it, the rotor is the only cool part. Are they way to big for the FB?

Did you use this write up to install these or did you install them another way??

Ok, I'm bringing this back to life....... Has anyone come up with a better way of doing the RX8 seat install? I'm not saying that the write up was not a good way to do it... its just been awhile and maybe someone has come up with a new idea. I plan on doing this seat swap shortly.

I read on one thread about someone installing fd seats and making them so that the passenger seat is a rigid mount without slider to make the 2 seats sit evenly. I wonder if this might help with the Rx8 seats.

I never let anyone adjust my pass seat anyways because they might smash into my storage bin.

Anyways, any new ideas? thanks

all this trouble for rx8 seats, huh? motherfucken wow...

:AA:

Well, as the guy who posted the original how-2 - I should follow up with the "didn't-really-work". These are damn heavy seat assy's - it the frames that are most of the weight. Both mine had the OEM welded-on Seat rails (ie, original to our RX7s) and these failed. The metal tangs that the bolts go thru to mount on the floor just wouldn't take the load and sheered. OEM rail mounts just too flimsy. So apologies if I have lead anyone astray.
The solution I came up with was to find (that is the trick) a set of after-market seat frame adapters, which are MUCH heavier gauge of steel and seem to easily cope with the -8 seats (theses are the _manual_ 8 seats, BTW, not the even-heavier electric ones). Happily most of the elaborate steel plates I originally fab'd onto the RX8 frames can be cut off, reducing the weight a bit.
BUT - because the RX8 seats are inherently WIDER than the '7s, you will still need some sort of support between the 8 frame and the 7 adapter - and I am still using a steel plate welded to the bottom of each side of the 8 seat rails to permit the 7 adapter to straddle and bolt on. I had to tap a threaded hole into these steel plates to bolt up the adapter. I will post some pics as I am just assembling them this weekend...

I will say, in spite of the initial grief - I LOVE THESE SEATS! They are comfy, look fab, and easily accommodate my 6'1" frame with a glass sunroof panel in place. Well worth the hassle, esp if you want to keep the mods limited to Mazda rotor-spec ;)

Stu Aull
80GS
Alaska

I did them in my car. completely differant than the OP will post pics in next couple of weeks. drivers side power seat, pass side man. pass side sits close to stock hight. drivers side is very easy close to bolt in after modifying the rx8 mounts. pass side requires fabing new brackets but fully functional. I have not found seat weight to be a problem. seat width is a issue of proper placement.

Thanks for the update!

Patiently waiting

dont forget the built in leg warmer man, love that on a long trip in the winter time

bummp

Hey guys -
just update my experiences with a SECOND re-install of RX8 seats in this thread:

https://www.rx7club.com/forum/showthread.php?t=802427

Stu Aull
80GS
Alaska

thanks to some of your threads on installing rx8 seats I decided to do it..

I picked up my set for $100, the kid delivered them and gave me a set of 1st gen seats to boot.. hahah

not wanting to drop $140 a bracket I decided to grab a tape measure and design my own set.. working as a machinist and having also been thru welding school before machinist school, I was able to design in solidworks then cut on the flowjet.. guessed the angle of the tab bends at work and they happened to fit perfectly... the slots no as much but it was all guess work..

My brother inlaw owns a company that makes industrial mixing equipment so I picked up 2 20x20 chunks of 3/16th steel and made them, then welded them to the factory slides.. previous owner had cut off the factory tabs etc...
"
I havent cut the passenger side yet due to the weird mounting for the tabs.. I have redesigns a passenger side modifying the original file but I need to confirm some things first... before I cut it out...




https://cimg3.ibsrv.net/gimg/www.rx7...519ef18275.jpg
https://cimg1.ibsrv.net/gimg/www.rx7...05fcd868c6.jpg

Wow. Machinist... def gives you a Leg Up. Best of luck with the install. Would be nice with all the electric doo-dads, esp for what you paid.
Suspect the leather/deluxe seats must weigh even MORE. We gotta be careful when we (well, me) only have 100hp to move all this stuff around!

Stu Aull
80GS
AZ