I have an '06 RX-8, Shinka edition. Its bottom seat cushion has a ridge, running up the middle, that pokes me in the butt. It's pretty uncomfortable, even mildly painful. Otherwise, I like the RX-8 seat a lot! I've spent several hundred dollars with an automotive seat upholsterer trying to modify the foam, but without success.

The challenge is that the foam is contour-molded to the seat pan, so it can't be replaced with a flat slab. All the upholsterer can do is to slice the top off the foam above the contouring, and glue on slabs of other foams of different densities. Since the problem is in the lower contoured foam, which must remain, this hasn't worked.

I've visited Recaro and Sparco dealers in search of a alternatives. While their seats don't have the RX-8's "ridge" problem, aftermarket seats that would fit have other issues -- overly confining bottom cushion (as reported by Car & Driver), too-hard cushions, no adjustable lumbar, no height adjustment, etc.

So I purchased a low-mileage RX-8 seat from a wrecking yard, and substituted its foam in my existing seat (to preserve the Shinka's unique color scheme). Same problem. This discomfort is apparently caused by the design of the RX-8's seat-cushion foam. It is not a problem I've experienced with any other seat, automotive or otherwise.

Has anyone else dealt with this? Have you found a solution?

 

Did you sit in your replacement seat before you bought it? Did it have the same problem? Could just be a problem with the seat pan itself...

 

Maybe get a motorcycle seat "Gel insert" and put that inside the upholstery

(They sell them for motorcycle applications, but should be fairly easy to adapt to a car's seat pan)

Sportbikes have very hard seat cushions, and people who ride them for long distances are always modifying their seats for comfort, it is a fairly mature market so you can find pretty decent solutions.

 

never noticed nay ridge on my 06 shinka...are you sure your seat is not broken?

 

I have a Shinka as well, and I love the seats on mine (yes, they are slightly on the "firm" side of comfort, but I prefer them like that, and I love the tan color & "Alcantara suede" inserts. M olution... I take a water break evry 3-4 hours on a really long drive (good chance to take a p1$$ as well) once I get up and walk arround, getting the blood flowing to my legs solves the aches.

Otherwise I have to drive vry agressively to keep the blood flowing by constantly shifting gears :-D

I htink your pain is a result of a firm seat, and not the "ridge" in teh seat