The rear seat backs are pretty heavy due to the metal frames in them and I figured it wouldn't be too hard to make them lighter. However, without the wall, there would be very little to attach the frameless seats to, so I hadn't given this project a shot until now.
I picked up a spare set of seat backs to practice on and took them apart. Haven't gotten past that, but figured I'd document it for when I do this on my actual seats.
Started with the smaller one and removed the top plastic trim by pulling straight out:
Then went around and pried this retainer off of the metal frame. It's stitched onto the leather, so once it's free, the leather is too:
With that all pried up, the leather and foam are almost free. There's one T50 torx bolt at the bottom that needs to come out and then you can separate them:
Leather is held onto the foam with some hog rings:
And that grey carpet material is just glued onto the metal frame. Pretty easy to pull apart:
Disassembly of the larger seat back is mostly the same. First the plastic trim comes off, then the leather is pried away from the metal frame and finally the leather is detached from the foam by removing the hog rings:
Armrest assembly is held in with one T30 bolt:
Couple plastic trim pieces to remove, couple leather flaps to undo and one long plastic "clip" to separate and then the leather can come off:
And once again, that grey stuff is just glued on and easily removed:
With everything apart, I weighed all the individual pieces. Here are the results:
| Small Leather | 1.3 lbs |
| Large Leather | 2.2 lbs |
| Armrest Leather | 0.9 lbs |
| Small Foam | 1.8 lbs |
| Large Foam | 2.3 lbs |
| Armrest Foam | 1.2 lbs |
| Small Metal Frame | 7.9 lbs |
| Large Metal Frame | 16.3 lbs |
| Armrest Metal Frame | 1.9 lbs |
Now comes the question of what I want to remove. I think I've decided that I'm going to keep the leather, foam and grey carpet pieces. Previous experience with folding the seats down tells me that the foam is doing a ton of work to keep cabin noise down, so if I replace it with some lighter stuff, I'll likely need to add some sound deadening in. I doubt that I can get some other foam and sound deadening to weigh less than 4 lbs, so I'll just keep the OEM stuff. Plus, that means the cushions will be stuffed with the factory preformed foam and not something I hacked together in the garage. Should keep them looking exactly the same as before.
Next question is how to mount the seats back in the car with the frame gone. This is where those grey bits come in. I plan to sew some heavy duty velcro strips along the top of them and then glue the carpet + velcro assembly to the foam. Will probably also sew some velcro strips onto the sides of the leather to be able to velcro both seat backs together.
Last thing to consider is the armrest. This will likely need to be stuffed with some other foam. I'll try to separate the armrest foam from the armrest frame, but it didn't seem trivial. No big deal if I have to buy something to stuff it with though, as it's just a rectangular prism.
Final weight savings to be seen, but should be around 26 lbs. Not bad!
Also, felt irresponsible to not give a big disclaimer about this work. I understand that part of the reason the metal frames are so beefy is to prevent stuff that's in the trunk from entering the cabin in the event of a crash. I feel okay removing this safety measure for three reasons:
- This car is far from a daily now. The most I put in the trunk is some tools that I bring to the track. This trunk will likely never see big, heavy, bulky items again. If it does (e.g. a spare for a roadtrip), it's getting ratchet tied down.
- The slon wall will help. While the carbon is more brittle in the direction that things would hit it from, it should still absorb some of the kinetic energy of the objects that hit it. With that said, I do understand that the wall stops helping if something hits it and makes a hole through which other objects fly through.
- I'm already thinking of building a crash/hard braking guard to go in the trunk. Will likely bolt/clip in underneath the parcel shelf and then clip into those cargo net brackets on the chassis rails. This could be a net or a piece of plywood or some sheet metal, I don't know yet. I want to add this because I really don't want to crack that rear wall. It's not inconceivable that a small, pointy object placed in the trunk could fly towards the wall under hard barking and crack the carbon, which would reaaally suck.
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