Bay Area Miata Drivers
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by nick
Looking ahead and looking back on the Miata, sports cars, clubs, and BAMD. Plus of course updates on my Miata.
Entry # 17 (3,280 Views) Posted on May 24, 2011
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The Urge to Upgrade
Few Miata enthusiasts can stand to drive a stock Miata for very long. Fortunately the world is full of parts you can use to customize and personalize your pride and joy. You can find these parts on eBay and Craigslist, at the junkyard, and on the local forums. When all else fails you can purchase them retail from an aftermarket parts supplier. The parts you install will make your Miata faster, sleeker, shinier, cooler, and more comfortable, all at the same time. Or maybe not. But certainly better. 
From Elise Seat Brackets. . . 
One of the more popular seats for a Miata are the fiberglass shell seats that come stock in the Lotus Elise. Comfortable, good support, lots of side bolstering, and small enough to fit, they're one piece so they don't fold forward--nothing back there in a Lotus anyway--and that makes them very light. Having had a fair amount of experience (a.k.a. "practice") on a number of Miata aftermarket seat installs, when Murat (newold) asked me if I could do something about lowering and centering the Elise seats in his MSM I thought I'd take a shot. Coming up with a design turned out to be not only fairly easy, but it made me realize that installing any seat in a Miata really isn't that difficult, as long as the seat is small enough to fit. 
When installing any non-stock seat in a Miata, you have to first decide if you want to use the stock sliders. Sometimes you need the seat to be lower than the sliders allow. In Murat's case, he already knew the seat on stock sliders was too tall for him to pass a broomstick test, a common measurement that's generally required if you want to run track days. So we have to go lower. This means that once installed, the seats won't move, so obviously fore/aft positioning has to be fairly precise, although in fairness the stock sliders aren't infinitely adjustable, but have a positioning notch every 10 mm or so. 
In just about every case where stock sliders won't be used, a good base for the install can be made with a pair of 1-1/2" wide straps that run from the front to rear stock seat mounting holes along either side of the floor pan. These can be made from either 3/16" mild steel or 1/8" aircraft steel (4130 alloy, a.k.a. chromoly), 17-1/2" long. The last two inches at each end have to be bent downward at about a 20-degree angle, and 13/32" holes have to be drilled in the ends for the stock seat mounting bolts. On the driver's side, the inboard strap has to be trimmed in front for the transmission tunnel, and the mounting hole needs to be offset accordingly (see diagram below). Getting the mounting holes located exactly right is tricky, but it helps greatly if you have a set of floor pans cut from an old Miata to use as a jig, something we hope to borrow from Adam's (adamvs) salvaged '99. 
Goodwin Racing sells these straps. They're a nice piece of work, made of high chrome steel with cross straps welded in for extra rigidity. They aren't cheap at $99, but worth it considering the quality, and they fit perfectly. The only problem, besides the price, is that they only make it for the driver's side. In any case you
can make the straps yourself without too much effort, and with an $80 savings, at least. 
Once the straps are bolted in place, it's just a matter of positioning the seat and either attaching side-mount brackets to the straps, or in some cases simply bottom-mounting the seats directly to the straps. The Elise seats are a bit more trouble, being side mounted in back and bottom mounted in front. Not only do we need custom-made side-mount brackets, but the bottom-mounts in front sit an inch or two above the actual bottom of the seat, so a crosswise mounting rail has to be bolted to the straps first, and the seat can then be bolted to the rail (see diagram). Fortunately, a lot of Elise seats have been installed in a lot of Miatas, and in some cases the installs have been documented online. 
After googling several photos, drawings, and diagrams (including those of BAMD's own NA-Eric), I was able to come up with a respectable design for a side mount bracket using 3/16" mild steel angles and 3/32" aircraft steel plate. We already know that centering the seat with respect to the steering wheels and pedals means that the seat will sit offset on the straps (toward the transmission tunnel), so the side mounts had to be designed with plenty of lateral adjustment. The best part of the design, for me, is that the mounts require no welding and no bending. Welding and bending aren't inherently bad, but avoiding them eliminates any potential for fabrication quality issues. It also makes reproduction of parts a snap, and allows for minor adjustments. Welding is kind of permanent. 
So the metal is on order and I'm looking forward to making the pieces. I'm estimating about 30 hours total including fitting, finishing, and painting. Of course with any engineering project, you have to take a look at the design and ask yourself what could be improved. Could it be lighter? Probably, but not by much more than a pound or two. Could it look better? Maybe, if the side mounts were a single piece with industrial cuts and bends. 
A welded design might look better still, depending on the quality of the welds. Some of the welding jobs I've seen online, I wouldn't be posting any pictures. Could the mount be more adjustable? Sure, we could slot the holes in the straps for more offset adjustment. So we have some things to think about before the cutting and drilling begins. 
For anyone considering installing Elise seats in your own Miata, you have a couple of options, or rather decisions to make. One is stock sliders vs. a Goodwin-style mount. Sliders add about 3/4" to the height. It doesn't sound like much, but it feels like a huge difference when you're sitting in the seat. If you go with sliders, there is at least one bracket available commercially, although I'm not sure how they deal with the offset, if they do at all. 
If you go with a lower installation using straps, you're pretty much faced with custom fabrication. That seems to have been the case with the vast majority of Elise seat installs. If that's your answer, you can use any of the online designs, or do what everyone else has done and come up with one of your own. Either way, you'll have fun doing it. 
. . .to Door Bars 
The Miata aftermarket is not huge, and it's getting squeezed every day by more products and more competitors. It's unlikely that anyone's getting rich out of the deal, but maybe a few Miata entrepreneurs can at least write off their racing budget as a business expense. Some of the biggest guns in the market are just getting by, particularly places that are exclusively Miata. If you can expand your market to other cars, you have a better chance. Trying to make a living in the Miata market alone is hard enough, but trying to do it with just one product takes either a miracle product or some really spectacular marketing. I can only think of one company that's been able to do it so far. To survive, you either need a day job, or you need to keep innovating like there's no tomorrow. 
One of the good things about the Miata community is that it's somewhat self-marketing. It has more than one national forum spreading information about which products are good and which ones are crap. There's still no such thing as a product that sells itself, but you can definitely tap into the Miata market if you have a better mousetrap. 
A few months ago Narek (BAMD's 92sunburst) came up with a better mousetrap in the form of Miata door bars. With a little encouragement from his friends, he invested in a small manufacturing run of the bars to see how they'd do on the market. It's still too early to tell, but it's great to see the bars starting to get some national attention, including a multi-page thread on (which unfortunately got side-tracked into a mongo safety discussion, but eventually gets back on point thanks to a post by Murat). Naturally BAMD is avoiding any commercial ties with his company, but Narek is a good guy, the door bars are a great design, and we wish him the best of luck. 
These are just a couple examples of the hundreds of upgrades you can do to your Miata. Installing a manufactured part is usually easier than fabricating something from scratch, but either way can be a lot of fun, both to install and to show off. And for me, the next best thing to doing my own upgrades is reading about other Miata drivers doing their own upgrades. 
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Comments (newest first)
2011-05-25 07:34:57 from newold_m
The seat bracket design is looking amazing Nick..! Thanks a lot and really appreciate your help..!!!