I’m determined to replace my E21 Recaro seats with the Recaro sport seats out of an E30. There’s nothing wrong with my E21 Recaros; they work perfectly fine and are comfortable. But the E30 Recaros are more supportive and comfortable and I’m a little nervous something will happen to the E21 seats (they’re quite valuable).
Lucky for me my car came with a set of original seats with sliders. And I have a set of beat up E30 Recaros to take apart.
From my basic Internet research there is at least one major hurdle to overcome – the E21 floor is uneven thanks to a raised section of sheetmetal on the outboard side. The inboard is also raised but not as much as the outside. BMW essentially made the floor uneven.
There is a 2″ difference in height between the factory seat rails to level the seat base (see photo below). The people who have installed E30 seats have cut this sheetmetal section out, then bolted the E30 seat rails to the floor. That’s what was done in the tan interior photo above. But I’m not OK with that kind of semi-permanent modification.
Here are the methods I have come up with –
Plan A: 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.
Plan B: bolt the E21 sliders to the E30 seat base. The E21 slider rails are simply bolted to the metal seat base with small machine screws. The E30 seat base (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 base 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.
Plan C: 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.
Plan D: 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.
There’s no deadline for this to work. But I’m determined so check back again for updates. I’m pursuing installing the E21 sliders to the E30 base but that means permanently modifying the E30 base by removing the fold-forward feature.