E30 Recaro Seats in E21

I’m interested in replacing my E21 Recaro seats with E30 Recaro sport seats. There’s nothing wrong with my E21 Recaros; they work perfectly fine and are reasonably comfortable. But the E30 Recaros are more supportive and I’m a little nervous something will happen to the E21 seats (they’re quite valuable).

Lucky for me the car came with a set of original comfort seats and sliders. And I have a set of beat up E30 Recaros to take apart.

From my basic Internet research there is one major hurdle to overcome – the E21 floor is uneven. There are two raised sheet metal platforms on each side of the car (an inboard and an outboard). But for some reason, BMW made them different heights! The outboard is about 2″ higher than the inboard. And BMW compensated for that with seat rails that are different heights. Crazy!

The photo below shows the factory seat sliders and their obvious height differences. There is a 2″ difference in height between the factory seat rails to level the seat base (see photo below).

Another photo of the floor showing the raised sections. The E30 seat sliders are much taller than either E21 so I can’t just level the floor with a spacer. The E30 seats will be much too high.

Others who have installed E30 seats will cut the outboard section out completely. Then used a steel C-channel welded in that is the same height as the inboard piece, leveling both sides. But I’m not OK with that kind of semi-permanent modification. I’ve also seen 2×4 wood block used, which sounds sketchy.

But I’m determined to find a way to make it work without hacking it apart so I can reinstall the E21 sears at any time.

Here are the methods I have come up with –

Option 1: install a matching raised section on the inboard side and bolt the E30 seat sliders to each section. Some people use a block of wood (which seems frighteningly unsafe).
Result: this would make the E30 seat too high. The E30 seat will always sit higher than the E21 because of the tall seat sliders – there is a 1.5″ gap between the seat base and the seat rail (the E21 has no gap). I have to keep that in mind with any work I do.

Option 2: bolt the E21 sliders to the E30 seat frame. The E21 slider rails are simply bolted to the E21 metal frame with small screws. The E30 seat frame is similar and there are existing holes to use.

The E30 rails use a combination of large bolts and sheetmetal pins to secure the frame to the sliders. The backrest and seat rake adjustments are part of the attachment to the sliders.
Result: the E21 sliders interfere with the rail for the backrest or the lever for the rake adjustment.

I could install the E21 sliders if I disable one or both seat adjustments. But it will be awkward without them. Awkward but not out of the question. The goal should be a full install without losing any function.

Also: the width between the E21 seat sliders is 42.5cm (16.75″) and the E30 is 41.7cm (16.4″). So even if the sliders did bolt to the E30 base, they would be too narrow to fit to the floor.

I really like the idea of using the E21 sliders because they are a direct fit to the floor, solving the biggest problem. So I need to find a way of attaching the E30 seat to the E21 sliders. This is the route I’m going to explore first.

Option 3: bolt the E21 sliders to the floor as factory, then use a thick steel adapter between the sliders and the E30 seat. If I design the steel plate correctly it will clear the adjusters for the backrest and rake.
Result: TBD. I don’t see how I can do this without the adjusters and seat hardware interfering with each other.

Option 4: use a floor mount (Wedge Engineering or Planted) for a racing seat with the E21 sliders or a set of racing seat sliders. Recaro racing sliders are 16″ wide but that’s easily changed with a longer adjusting rod between the sliders.
Result: TBD

Option 98: cut a section of the outboard piece to level it with the inboard. Almost two inches needs to come out. It’s a permanent modification so I consider this an admission of defeat. The upside is that I could easily add a spacer to put the E21 seats back in. And it would keep a factory appearance.
Result: TBD. I’m not wild about this one.

Option 99: the last resort. Completely cut out the outboard piece and weld in an iron bar – just like everyone else.

There’s no deadline for this to work. And it’s been a few years since I made this post. I will be removing the seats and carpet in a future project but that will be 2023 at the earliest.

Side note: the E30 seats are not really Recaro. There was a true Recaro seat for early E30s sold in Europe only. The US seats are similar but not made by Recaro. Technically they are E30 Sport seats. But I will still refer to them as Recaro.