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MG MGB GT V8 Factory Originals Technical - Miata Seat Mounting System

Friends,

I see that some of you have converted to Miata seats.

I have the rails and brackets prepared but can't get a good match for the mounting holes.

Does anyone have a good formula and dimensions for mounting the seats (holes, mount height, pitch, etc.)?

Thanks in advance.

J.B.
J.B.

If you remove the stock seats and fill the captive nuts with studs about 1 1/2- 2" long, it makes everything easier. A trial fit of the Miata seats shows that the front Miata mounting holes almost line up with the studs in the floor. A rat tail file or Dremel will make that a fit. Fender washers will make the bolt up secure.

The rear Miata mounts are extensions rivited to the frame. If you drill out the rivits, they can be re-positioned and reattached either with a nut & bolt or by MIG welding. I have done both with equal success.

Sorry, I never recorded the rear leg positions. Keep the seat frame parallel to the outside sill and work off that point.

Left & right seats have slightly different locations but both can be located the same way. I like using studs, washers and nuts in place of bolts and washers, but either system works.

Hope all this makes sense and helps you with the fitting. E-mail me direct if you need more info.
Jim Stuart

I may be able to help you out as well, J.B. I did this conversion to my V8 roadster a while back.

Briefly explained, I made up a template of the factory floor holes and made up brackets to fit these. As Jim says, the seats line up pretty well on their own or at least the driver's seat does. For some reason, Mazda moved the passenger seat inside rail out an inch. I made spacer-brackets to over-come this.

If you want to contact me, I can provide more info and pics. FWIW, I used the first generation seats (with the speaker cutouts in the headrests). I don't know if the later seats have the same rail dimensions.
Simon Austin

simon
I would be interested in more info please re seats photo's etc.
Thanks Tony Zorzo
T Zorzo

I am 6' 7" tall do the Miata seats give any more leg room? I moved my OE seat rails aft about 1.5 inches from stock and this works OK. Also are the seats more suitible for trips with less back pain than a good set of OE seats?

Thanks,

Mark
M Mallaby

I mounted Miata seats with no problem in my MGBGTVV8 and TR6. I put driver on passenger and vis versa. Seemed to fit better. I made my own mounting rails with studs. Very easy to do. The seats are much better than stock, look correct and are easy to adjust. I spent lots of time and money restoring the TR6 seats and would never do it again. Change to Miata seats and don't look back.
Richard Porter

Tony,

I'll get some detail pics together and send them off to you. This site will show you what they look like installed:

http://www.britishv8.org/MG/SimonAustin.htm

Mark,

The seats provide much better support than OE seats. Good side bolsters and I had my upholsterer leave the lumbar area unattached on the sides so I can add more padding if I like.

Using the original captive nuts provides the same amount of leg room as OE seats so moving Miata seats back should work as well. If you're not concerned about using the captive nuts, you can mount the seats wherever you need to.
Simon Austin

Mark,

You need to go sit in a Miata. The leg room is not any different (with the seats not the two cars) as far as I can tell. Miata seats are great for those 5'10" & under. The back & back support is not ideal for taller people. I'm 6'2" and I don't find them very comfortable. My dad is 5'5" and loves 'em.

I have them in my '79 B. I found no need to swap the driver & passenger seats. I used the stock mounting holes & bolts. Here's the way I did it:

I cut off the front Miata mounts & welded two 1.5" (approx) Ls for the front "feet" to give some rise for thigh support.

In the back, I straightened the rear Miata mounts to be parallel with the seat tracks. This lowers the seat but causes the seat bottom to hit the floorboard. The Miata seat bottom is thin mild steel so it was bashed in for clearance. The rear mounts are held on by two rivets. I removed the outer rivet & swiveled the mounts inward to work with the stock MG mounting holes. Welded them in place. Once the front was bolted in place & the rear was located, I welded fender washers on the rear mounts since the Miata mount bolt holes are much too large.
Carl Floyd

I've had my Miata seats with headrest speakers for about 7 years now and really like the comfort. I have lower back problems and they are kept away with an inflatable bladder available through Moss Motors, Vicky Brit, or anybody else who sells Miata accessoreis. Mine haven't leaked yet and can be easily inflated or deflated. I also switched the seats to the other sides. Better access to the reclining mechanism.

I particularly wanted the speakers in the headrests, as they don't require a lot of volume to be heard. I used Infinity Reference 3.5" two-ways, and am very happy with the results. No bass notes, but that is easily fixed with a pair of 6" subs mounted in the holes PO cut in the wall behind the seats.
Bob Fish

That turned out much easier than expected. Thanks Jim and Simmon.

I ended up cutting and welding. On the left-hand driver's seat, I cut the front feet off and moved them over about half an inch. Drilled out the rivets on the rear feet and swiveled them align with the holes. My goal was to move the seats over to the side rails as much as possible without fouling the recliner mechanism. Passenger seats were easier to modify (always is the second time around, isn't it). Measures about 12.5 inches center-to-center between the holes. I also trimmed about 1 inch from the rear rail, but think this is not necessary. I initially used bolts (no. 18 x 28 x 3/4 inch) with big fender washers. On final fit, I went with Jim's stud idea, which greatly simplifies the fitting (the studs find the holes and you're off and running). Also through thick rubber grommets under each mounting leg for cushioning and vibration reduction.

Mark, I find the Miata seats to give a slightly higher attitude than the stock MGB seats. Much more comfortable, I think. At 5'10 I feel cramped, but maybe its my widening rear and tummy. I might want to pitch the front of the seats up a bit, say about an inch or so, for thigh support. Instead of modifying the brackets again, I might consider a spacer between the seat and the brackets. We'll see how they do before further modifying.

Thanks again Jim and Simmon!

J.B.
J.B.

After trying different seats in my B, i finally ended up with Saab 9000 seats and can only tell they are perfect and now i know why these Swedish cars are so expensive.

The seats are not an easy swap and have to be modified i.e. three of the four motors removed, subchassis cut down and weldet to the lower sections of the B seats. The LH seat from the Saab must be used RH and vice versa on a B. These seats can also not be slided as far to the front (on MK II and MK III cars) as the Leyland seats but are much more comfortable than those used in our BMW and Mercedes, although they are both not fitted with cheap uphostery.

Try to have a seat in a Saab 9000 and have a look upon the seats from underneath and you will see the difference and know why they are so fantastic, not even for looks and finish but also for long distanc journeys and even serious competition too.

Ralph
Ralph

Simon
Thankyou for the photo's and comments therein.
Tony Zorzo

You're welcome, Tony. Happy to help out.

Cheers
Simon
Simon Austin

Thanks for the info guys. At 6"7" the last thing I need is to sit higher off the floor. My forehead already catches enough bugs.

Mark.
M Mallaby

I envy you guys with all that space in those nice tall MGBs. To get the Miata seats to fit in my MGA based car, I not only had to remove the rails, I had to also create a dropped florr for the seat bottom to fit into.

We welded strap steel to the frame or mounting the seats (but remember that the stock MGA floors were wood, so we'd have done that anyway).

Something else I had to do was swap them side for side as there was a bulge in the seat machanism that wouldn't otherwise clear the frame. Do MGBs have any problem with that?
Bill Spohn

"Something else I had to do was swap them side for side as there was a bulge in the seat machanism that wouldn't otherwise clear the frame. Do MGBs have any problem with that?"

No. I didn't have to swap them. The mechanism just cleared on my '79.

http://www.britishv8.org/MG/CarlFloyd/CarlFloyd-I.jpg

I did take the seat bottom apart & scoop out some of the foam cushion with an electric knife to sit lower. I need a lowered floor so I won't have to build such a tall rollbar.
Carl Floyd

I didn't swap mine either.
Simon Austin

Did you guys who didn't swap your seats, use the mg front bolt holes,and drill new ones for the rear. This is what I did but I swaped them. I think I tried to fit them without the swap but didn't seam to work using the front holes.
DBW

I used only the original floor pan nuts & bolts.
Carl Floyd

I think Carl and I must have done the same conversion and not realized it. I used the original holes as well.

I made a template out of peg-board with the layout of the captive nuts on it. This allowed me to manipulate the Miata brackets to fit into these holes before I bolted them into the car.

The front mounts are the most work to get to fit because, in my case, I removed the Miata brackets, enlarged the holes and put bolts through these holes into the captive nuts.

I wanted to use the captive nuts as these sit right above the fixed cross-member and I didn't want to drill through this to attach new bolts.
Simon Austin

This thread was discussed between 27/03/2007 and 09/04/2007

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