Firstfives.org

My seats are falling apart. I have some e34 seats and found that although my car is a '79 it has the earlier floorpan with three studs per side and the floor hump, which is not compatible with the e28/e34 seat rails unlike the later (80-81) e12 chassis which have the two boltholes and flat floor.
Does anyone know what other BMW chassis' have the same floorpan and seat rails as early e12s that would interchange? The firstfives FAQ lists the rear seats but not front.
Reason I ask is when I go to aftermarket sites like Corbeau, they tend to list the same rails for e12 as e28, which is only correct for '80-81 and to make sure I'm getting the right part first time I'd just like to order the seats for a chassis that has my earlier style floorpan. e3, e9, e10 maybe?

Are sure both sides are the early style? My '79 had the later style on the drivers side and the early style on the passenger side. Regardless, and it's been a while, it seems like the seats were the same, mounting wise, just that the drivers side had the separate removable base allowing tilting of the seat up and down in either the front or the back. Again, IIRC, the passenger side just used rails mounted to the bottom of the seat. So what would you be mounting the seats to, the base or the floor itself?

I have a 1975 with the passenger seat out. Definitely a different rail system than the driver side. I'll get some pics later this week.

Here's some photos - and you're right my passenger side has the raised frame due to no seat tilting option. I was going to tackle that later because it seemed like a huge pain. Can this metal sheeting be cut away, and if so, what's underneath?
You can sort of see in that photo the hump in the middle, where the 3rd pair of center bolts are. It's definitely not flat.
But drivers side is definitely not compatible with e28 rails. And the e34 seats won't bolt onto e28/e12 rails because it's a whole different assembly.
Replacing these seats seems like it will be painful.

Hey Mike, ideally I'd mount the seat directly to the floor not the e12 seat mechanism. I was thinking of getting some rectangular steel tubing that's same size as that hump, drill a hole for the floor bolt and drill another hole on the top that matches up with the e34 seat base. Then grind of the middle bolt, and if all the measurements are correct the drivers seat should sit flat and the bolts should all line up.
Todd let me know if you have any pics of what's under the carpet on the passenger side, whether it looks like it comes out easily or not.
I have no idea what's under the carpet on the passenger side but I get the sense it's a base welded into the frame under carpet. I could put the e34 seat in there but it'd be a couple of inches higher than the drivers seat, look weird and the headrest would almost certainly hit the ceiling. I could possibly hack it all away and try and mount to the actual floor, but there's a sealed cavity between the floor and the underside of the car where I'd want to locate bolts so if I destroy that side I could end up with no ability to have a seat there at all.
So e28/e34 seats won't fit easily. Any other e12 seats will all be as wrecked as mine, so I was hoping to get aftermarket seats (rather than rebuild and reupholster my originals) and be done with it.
As I've seen they all list the same rails for e12/e28 so I predict I'll get a seat that just won't fit and I'll have to send it back.

I've got an early car as well with the humps and different raised thing on the passenger side. My plan for getting rid of my deteriorating e12 seats is to bolt e21 Recaros to the existing e12 seat rails. Lock I realize you already have the e34 seats but maybe its easier to get seats that bolt right to the rails. Just a suggestion.

That is what I"m thinking. The seats are from a e34 parts car so I'm not committed to using them.
What you said it made me think maybe that's what the aftermarket seat makers assume - their seats don't bolt to the floor, rather the existing rails which is an e12/e21/e28 pattern. In which case, then I'll leave the rails there and have comfortable and contoured seats.

And the Recaros bolt right to the e12 , e24, e28 seat sliders with the standard e21 adapters. Recaros aren't cheap or that plentiful these days but I figure if I get tired of them or want to change to something else the would be easy to sell. I'll be posting some pics in a little while in my project thread. I plan to have them recovered in red vinyl when I get around to dismantling them.

Here're your new seats, rails and all!


https://bringatrailer.com/listing/recaro-2/

Great catch! The detailed photos are useful.
I'm also considering lending my car to www.plantedtechnology.com for them to take measurements and add an e12 base to their inventory.

Never heard of them until now. Good resource, thanks.