My quest for more headroom - custom moulded seat cushion

[Geraint]

Now then.

I’ve owned my NSX for a couple of months now and just haven’t been able to get comfortable in it.

I’m quite a big fella (6’4” and about 16st), not ‘all legs’ and so headroom has been a real issue for me. It seemed OK on the test drive but I suppose I was excited about the car and busy trying to assess its condition, so it didn’t really hit me as a problem.

However on the long-ish drive home, and then on another couple of long trips in it (3 hours or so) I found that my head was very close to the roof, and I was tensing my shoulders to pull my head downwards away from the roof. Not good.

I could adjust the seat to make it a bit better, but this resulted in bizarre positions with bent/splayed legs, weird body angles and extended arms. Not really ideal for enjoying the car.

I looked at various options, including the Dali seat cushion, a pair of Recaro PPs, the Downforce seats, the SOS rails etc, but they all seemed less than ideal and/or very expensive.

As part of my research, I tried the standard seat without the cushion, and found that it transformed the seating position for me. One friend suggested a moulded custom cushion (like they use in single seaters), another offered an old camping foam mat, and soon a plan was formed.

The plan was to create a moulded seat base to replace the OEM item using two-pack expanding foam, tidy it up and then get it trimmed in black leather to match the rest of the interior.

The moulding is done by mixing two liquids together, putting the mixture into a bin liner and then sitting on it while it moulds and then sets.

With the OEM cushion already removed, I taped around the edges to stop the mould finding its way into the crevices under the side bolsters:

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat1.jpg

Then protected the interior with polythene sheet, again taped to stop it moving around

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat2.jpg

Bin liner in place, to check it was big enough to contain the foam

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat3.jpg

Two-pack foam ready for mixing

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat4.jpg

[Geraint]

Mixing the foam using an old milk carton. Need to ensure thorough mixing but not a lot of time to mess about, as it starts reacting quite quickly...

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat5.jpg

Mixture placed in bin liner, ensure a thin layer was spread across the floor of the seat, then driver installed. I wore some winter cycling leggings to give a bit of padding without the seams/pockets etc that come with normal trousers, that might affect the shape of the mould.

The moulding process itself takes about 20 minutes, you feel the foam reacting, warming up and expanding, quite an odd feeling but not unpleasant. Need to sit still in driving position while it moulds and then sets.

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat6.jpg

Result of moulding process:

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat7.jpg

Removed from car:

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat8.jpg

[Geraint]

Re-positioned:

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat9.jpg

You can see from the above pic that the foam is very thin in some places, this is where there was a lot of pressure between the tops of my legs and the raised parts of the seat. I did some smaller secondary moulds, using the original foam, a bin liner and a smaller amount of mixture, then reinforced the thinner parts with some fibreglass as shown in the next pic

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat10.jpg

Then trimmed the moulded part down and tidied it up. The foam sets quite hard, it’s very much like that domestic foam filler you can buy in aerosol cans for filling holes in walls etc. I decided to give it a layer of softer foam from the camping mat I mentioned earlier, just cut roughly to size, affixed using spray glue, then trimmed to fit.

The result

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat11.jpg

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat12.jpg

[Geraint]

Comparison with the OEM seat cushion, showing the difference in height

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat13.jpg

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat14.jpg

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat15.jpg

[Geraint]

Then had it trimmed in leather at a local place, this took a while but the place was busy, I wasn’t in a rush and I wanted a nice job. The face is very nice leather, in my opinion nicer than the OEM stuff, and the sides are vinyl.


http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat16.jpg

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat17.jpg

Fitted to the car:

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat18.jpg

http://i294.photobucket.com/albums/mm104/gce68/NSX/NSXseat19.jpg

I’m delighted with the results, it’s a nice custom job, something a bit different, keeps the interior mostly OEM and worked out cheaper than any of the other options I looked at.

Hope this is useful for anyone else in the same boat as I was.

I’ll be at Japfest, anyone who would like a closer look at it will be more than welcome

Contacts
Foam: Merlin Motorsport, Castle Combe www.merlinmotorsport.co.uk
Trimming: Krych Trimming, Bristol www.krychtrimming.co.uk

[Nick Graves]

Nice job!

Let us know how ergonomic it is on a longer journey.

I know it's missing the obvious, but I find the idea of someone being too tall for a -T intrinsically funny. I had a friend of similar height who could only properly drive his FIAT nuova 500 with the sunroof open.

[Geraint]

Thanks :)

Yeah I see your point about headroom in a targa - having tried a S2k I think I'd have to leave the top down all the time :)

The problem is that my head isn't under the targa panel, it's under the hoop, so removing the panel doesn't help :(

[Ewan]

Some lanky bugger trying out my -T for size ...
9022

[nobby]

good job, hope it works out for you on those longer journeys

[SILVER BULLET]

Brilliant solution to your problem Geraint and looks very professional , not something that's troubled me being 5'-6":laugh:.

Cheers,

Ian

[Justin]

As everyone's said - NICE JOB! :beer:

It's great to see people working out elegant fixes to various issues... this one's pretty ingenious!

My only question is the hump separating the two legs. I would just wonder if this affects operation of the pedals - particularly heel/toe changing - and whether it would become restrictive on slightly longer journeys.... Suppose only time will tell, so keep us updated.

[TheQuietOne]

That has to be one of the strangest mods I've seen, but I'm sure it does the trick. Having sat on the Dali one your solution has to be more comfortable too, it's like a piece of stone wrapped in vinyl!

[Geraint]

Thanks for the interest & comments chaps :D

Justin - fair question about the 'hump'; I did try some heel & toe with it before I had it trimmed, it didn't seem to intrude at all. I find I don't have enough room in the footwell for big movements anyway, so heel & toe for me is more a case of 'inside outside' ie roll outside of foot onto throttle while braking. My upper legs don't move much & the hump doesn't really seem to be a problem. The only slight issue is getting in & out, it's a tighter squeeze to get my left leg through between the hump & the wheel, but it's not an 'errand' car so I thought I could live with it.

TheQuietOne - thanks for that info on the Dali, makes me feel like this probably was a better solution for me.

Time & mileage will be the true test, I'll let you know how I get on :)

[nobby]

your size, weight etc is very similar to my own, i perhaps am slightly longer in the leg according to your description, but i have yet to get really uncomfortable during long drives in my NSX ... the only thing that tends to give me bother is my right knee and for some reason its dodgy at the mo!

I find headroom etc to be OK and the seat provides a good range of adjustment in order to get sitted properly. I done a whack of miles in Switzerland etc last year and my knee gave up before the rest of me ... i also think i have reasonable clearance in terms of headroom but if the back of my seat was more upright i guess i could find myself in the same position as you. but hopefully your 'fixit' sorts out your problems and you begin to enjoy the NSX as a proper GT car

[Nick Graves]

I heel & toe like that, too; a wide-soled trainer does the trick. Heel only ever leaves the floor for a big-rev downshift.

Honda does know where pedals ought to go, unlike so many other manufacturers.

[gumball]

Looks good, no doubt inspired by a formula 1 seat fitting method. I probably would have left the centre a little flatter, but I bet it's lovely and snug.

[Justin]

I heel & toe like that, too; a wide-soled trainer does the trick. Heel only ever leaves the floor for a big-rev downshift.

Honda does know where pedals ought to go, unlike so many other manufacturers.

I agree that the Honda pedals are well sorted for this, but I tend to where thin soled trainers for driving and am constantly worried that my size 9 would end up slipping off the brake, or getting stuck between the two pedals! :eek:

Geraint - glad it's working well for you :)

[WhyOne?]

Nice work.

This is the same technique as they use to make seats for F1 cars, so no reason it shouldn't provide a good driving position.

[Geraint]

Thanks again chaps :)

I spent about 6 hours in the car today, combination of slogging along the motorway, 'pressing on' across Exmoor, some crawling around villages, and jumping in and out of the car quite a lot.

First off, it's fixed the headroom problem I had. I'm still close to the roof, but didn't bump my head once despite some compression/elevation events on the bumpy moorland roads. So I've stopped thinking about that and am relaxed in the car now.

In terms of, er, 'rear end comfort', I found it supremely comfortable. I felt no aches or numbness at all, and found it very supportive when pressing on as the 'hump' provides support to both legs when cornering reduces my tendency to slide forward under braking. I didn't find it an issue getting in & out either. It's more comfortable than any seat I've used before, including decent Recaro sports seats & nice OEM stuff from Porsche, BMW, Saab, Honda etc.

I thought hard about what I'd change, and I couldn't think of anything at all, I wouldn't flatten the hump, add more soft foam, nothing.

I'm chuffed to bits with it, it's solved the main problem I had (headroom) but has also added a new dimension of support & comfort that I haven't experienced before.

It was only one day, and longer term use may throw up some issues, but so far, so good :)

[TheSebringOne]

Congratulations! Sounds like a successful DIY modification.

[Crockefeller]

Bumpy bump bump!

I'm thinking of doing this mod to my own car in the new year. If I can't find a comfy driving position I'll be forced to sell, which I really don't want to do....

At the moment I'm on the aluminium shell which is OK for 20mins but then it's numb legs time. How much thickness on top of the alu shell does this method add Geraint?