I don’t mean to complain about the stock front Alto Works Limited sport seats seats, as they are actually quite good for an economy car. They have good bolstering along the thigh and lower back, so they feel somewhat supportive during spirited driving. I am generally pretty impressed with the comfort and, of course, they are still easy to get in and out of. However, I feel I sit at a rather high position for such a low car. So, with many things, they can be improved.
I picked up a virtually free trick from the Miata.net forums to get a lower seating position and increase side bolstering on the stock seats. All that is involved is some zip ties, some cutting tools, and a few hours of free time to cut out the foam in the seat. The Miata guys call it a “foamectomy.” The Miata Roadster seats actually have a relatively thick pad of about 4 inches so it is quite logical to cut some out in order to get a better seating position.
I actually did this on my own NA8 some years back before I picked up a Lotus Exige-style bucket. I am about 6 feet tall (182 cm), so it was necessary to get low enough to avoid hitting the roof of the car. Since it was so successful, I thought it would do wonders for my Alto Works.
The only drawback is that it is a permanent modification to the seats and does potentially ruin the comfort of the stock seats, but I figured if I mess up, I could always just buy another replacement stock seat or go full bucket. I have not much to lose.
Remove four 12mm bolts on the rails and one hidden under the center console, disconnect the seat belt sensor connector, and the seat is removed easily. I used this chance and cleaned up the carpeting.
Looking at the brackets, the seats were made decently low from the factory, as the seat sliders are bolted directly to the bottom seat pan, offering little space for further welding modification short of discarding the sliders and bolting the seat straight to the floor. As a two-door car, that’s an unreasonable change at this time, since accessing the rear seats from time to time would be a necessity. (Not to mention slightly worrisome, as my amateur welding ability could prove dangerous in an accident.)
To undo the upholstery, there are several metal rings that need to be bent and removed…Well, crap. The foam on the seats is surprisingly thin as it is, around an inch (3 cm) thick. I was considering giving up, but Matsuda-san suggested I simply re-adjust the springs. Not a bad idea! By leaving the front spring at a high perch and progressively lowering the rearward springs, it creates an decline where my rear end sits more deeply into the seat.
Relocating the springs to near the bottom of the panel gave me around 25 - 30 mm of lowering, which is quite a lot considering it is still on sliders. After multiple test sittings, I found that it felt more comfortable than the stock seat. My ample rear end could not feel the metal plate, zip ties, or springs.
Reassembly is a matter of just reversing the whole process, but instead of the metal rings clipping the upholstery to the frame, I just used zip ties to put the cloth all tightly together Saves time and works just as well, minimally affecting the looseness of the fabric, if at all. So how did it turn out?
I think it came out really well. The seat feels noticeably lower, especially when compared against the non-modified passenger seat. As a result of only the rear of the seat being lowered, it feels as if the bolsters are “cradling” me more, creating the illusion of added side bolsters without the need to replace the seat with something less livable day-to-day. A full bucket will come, but at a much later time. Right now I’m sitting pretty happy.
If you’re a bit handy, you can give your own seats a shot. I’m sure many stock seats can be modified in some similar way, as long as you don’t mind making potentially permanent modifications.