I have found that the sides of the back of the seat are very good to hold you in your seat but the seat itself, on mine, I think probably needs to be reupholstered after 18 years of use. As I am a bit short in the leg I found that the seat underneath my thighs was a bit uncomfortable so I changed the angle of the seat by putting two packing pieces under the two rear seat retaining bolts to lift it up about 20mm. This relieved the pressure on my thighs and made the seat a bit more comfortable.
What might be part of the problem, particularly on older cars, of seat discomfort, might be the seat base foam starting to rip through.
Metal wires are moulded into the seat, to help give lateral support. Over time, these rip through the foam, and the seat becomes less supporting; you might even feel the wires.
This is a scrap seat I recently stripped down; its from a 96-97 car, so the seat is slightly different in shape, but the principle is the same. You can see where the wire is starting to rip through, yet this seat felt fine with the covers on. A lot of older seats now need seat foam repairs
IL Motorsport used to sell genuine replacement foam parts for £100 each, but these are now discontinued. It ought to be possible to effect repairs to the foam though.
I would be careful about getting soft seats - Renault seats are soft - but they can ruin your back - I know, My Scenic seats were so comfy I had to have an £8k spine operation - since then I bought a Recaro that I have transferred to each car I have had ( currently in a Mondeo ) - it cost £1200, but it’s done over 200K miles and it’s still like new - it’s also like a church pew to sit on, but I can drive for hours without pain now. I have the standard seats in the MX-5 ( Mk1 Eunos ) and find them ok - I think firm seats are better for your back so think carefully before getting something that feels comfy initially, but offers little support long term - I ended up in a wheelcghair it was that bad !
On another point - the drivers bolster that wears, what’s the “normal” procedure for fixing that ?
I recently won these on the bay and the chap said he had had his old seats ('97 car)reupholstered and new foam added. Apart from I now slide from side to side (I’m a skinny wretch) they are far more comfortable than my old seats adding weight to the arguement that the foam degrades over time.
I don’t know about “normal” but this is how I temporarily repaired mine about 3 years ago and it is still OK.
Find a piece of cloth material that is about 2" larger, all round, than the worn part of the seat that is a similar shade/colour to the seat, and carefully insert it under the seats worn material. This is the tricky bit, you need to find someone, a lady I think, that knows how to darn, as in darning socks with holes in. Find a ball of wool that has similar colours in to the seat material and then you darn the worn part of the seat to the piece of material you inserted beneath the seat material.
Due to knee problems I now don’t use the bolster side of the seat to get into the car, I position my self in such a way that I slide into the seat using the back of the seat as support.
Actually, there was a commercial product that was neat in apperance; the company that made it has long gone, but maybe I will have a dig around.
Basically, it was advertised as a Miata “Seat Saver”; to stop your bolsters wearing, but it sould also be used to cover up unsightly wear. Essentially it was a simple length of black leather, with finished edges, with velcro at each end. You were supposed to feed this under the the back central pad (the central part of the seat is seperate from the rest, and attach the ends around the back of the seat.
The 3 different types of factory seat used in the Mk1 give different amounts of support. The fixed headrest seat of 89-93 UK and 89-95 Japan gives the best thigh support; there might be a little difference in 93-95 Roadsters, since these switched to a fire retardant material and possibly other changes (though the new material wears horribly). 95-97 fixed headrest Roadster seats give better lateral support, but poor thigh support. They also sit a little higher. The seats can be combined in a Frankenstein fashion.
The “Driving” seats I have were a factory option 91-93; the biggest difference is that the frame work was modified to give much deeper side bolsters than standard.