Sport vs. comfort seats bolt length issue

[hozzziii]

So I bought some sport seats. Cool.
Cleaned them up, greased all I could, fine.

Then I tried to install them, noticed this curious issue. The bolts were too short for the new seats!
Look here;
These are my old seats:
Here you can get a good idea of how thick the base is.
It's around 3 millimeters for the lower round part and another 3-4 millimeters for the two layers up top.


And then there are the new sport seats.
I took these pictures in the car, this is the driver's seats btw:

There is also that round part under this that you can't see in the picture. It's wedged into the carpet and it sits on the chassis.
So as you can partly see, there's the round part under, then the first plate above that, then there's this neck part that looks like a nut but I'm not sure if it is cuz it's not threaded then why is it a hexagon, then there's actual rails up top and then I can put the nut on.
What that results in:
Front left:

The nut barely catches all the threads from the chassis.
Front right:

Like, not great but not terrible.

Unfortunately it's much worse at the rear.

Like that's just half the threads! Not good at all.

And the 4th bolt that goes into the chassis instead of coming up from the chassis does not reach the threads at all, so no bolt.
I can just buy a longer 8.8 bolt, that's fine.

But I mean, it's not good, is it?


So I have two somewhat okay points of attachment at the front, at the rear one half engaged and one in need of a longer bolt.
I can buy the one bolt longer, not a big deal.
But I can't make the bolts that come up from the chassis any longer can I? So what do I do?

My first thought was, somehow shorten the seat "stage". Like cut one of layers but I'm not sure if it would be a clean job or even safe.

So, any thoughts?

[hozzziii]

Would really appreciate some ideas folks, thanks <3

[ghrays]

The seat rails in early (pre-9/85) seats are different than later seats. The comfort and sports seats rails are otherwise identical. If you are attempting to install later style seats in an early car, you may have difficulty as detailed here:

https://www.r3vlimited.com/board/forum/e30-technical-forums/appearance-cosmetic/interior/315882-seat-bolt-question-newer-sport-seat-in-older-e30

[hozzziii]

The seat rails in early (pre-9/85) seats are different than later seats. The comfort and sports seats rails are otherwise identical. If you are attempting to install later style seats in an early car, you may have difficulty as detailed here:
https://www.r3vlimited.com/board/for...t-in-older-e30

Well thanks, yup that's it. The people in that thread also had my issues. And the last post said that the studs are welded to the body.

So far I just bought a longer 8.8 bolt for the inner rears, and bolted the seat down, I got one about 1.5cm longer than the oe one, got the threads started around 1cm before it bottomed out.
I am still anxious about the studs and not getting my threads engaged all the way.


I did see a post here a while back, someone used something like a long nut, what am I saying xD, like a nut that engages the studs on the car all the way and still has about an inch of threads left, so they just got bolts for all four corners and well, that's one way to do it.

I guess the downsides are you raise the seat around less than 2 inches but that's not bad, but you are kind of putting all your hopes in terms of safety in these long nuts. Which honestly I'm not sure about. Could be fine but, ehh.

So yeah I just got a longer bolt and the others are just barely fine imo. But any idea is appreciated.

[roguetoaster]

Grind the seat rail nub down to accommodate the height change.

[hozzziii]

Grind the seat rail nub down to accommodate the height change.

Yeah that was my second idea, I guess this is the one that has the least damage to stuff, would probably do this. Thanks man.

[raymang]

Yeah that was my second idea, I guess this is the one that has the least damage to stuff, would probably do this. Thanks man.

Hey dealing with my own Recaro swap on an '85 325e with the early model rails and was wondering if you ended up grinding the seat rail nub down. Did it work? I'm sort of considering using jam locknuts as kind of a last resort but I don't mind grinding the late model sliders down a bit.