E21: Seat Fitment Guide:

Swapping seats round in a BMW E21 3-series is a nightmare, thanks to the floor-mounts being two different heights. To fit level-based seats from another car requires chopping out the welded floor-mounts and once this is done there is no going back.

1. Check if your floor-mounts have been chopped:

Check the outer floor-mounts on either side, spot-welded in place just inside the door-sill. They should look the one in the left photo below.

If they don't, and they look more like the right photo [with or without the wood], then you have chopped mounts and seats not originally from an E21. You also won't be going back to E21 seats very easily, so to preserve the style and make the ride a lot better, throw in seats from a newer BMW.

2.1 Fitting stock BMW seats from E30, E36 etc. :

This makes sense. E21 seats are sprung and uncomfortable and were dropped in almost every succeeding model. Other BMW seats are easier to come by and cheaper. E30 seats preserve the look almost identically and are far superior in construct. They also fit the inner seat mounts on the E21, the ones against the trans.-tunnel, so only the only outer ones need adapting. I am sure this is the case with seats from other 80s BMWs, possibly the E36 and E46 as I've seen it done, but need confirmation.
Modifying the outer floor-mounts, the ones against the door sills, is impossible as they just sit that much higher than the inner ones, the E21 of course having a crazy odd-height sub-frame design, so they need cutting out. Putting in new ones is pretty straight forward though, you can fabricate them with steel or alloy C-channel, wooden blocks, improvised stilts - these are all popular methods. Tilt-forward seats don't tend to be very strong anyway, so the new mounts don't have to be rock solid as long as they're bolted or welded securely to the floor-pan. Mine used the stock inner floor-mounts and a wooden block on the outer side to get the height - this presented no problem to the UK MOT (roadworthiness-test).

Check out my guide here: http://e21dub.blogspot.co.uk/2013/09/e30-sports-seats-fitted.html

Or check out HSVTurbo's guide HERE [where I got my idea] in THIS THREAD on bimmerforums.

2.2 Fitting rigid Racing bucket-seats:

If you're building a track car then it's obviously best to keep things as stiff and secure as possible. The neatest and most weight-saving method is to cut some steel cross-beams to fit and weld them across the floor-pan, from the trans.-tunnel to the door-sill. This could be done with or without removing the outer floor-mount, but you will probably have to do this to get the seat low enough. Two cross-beams under each seat would probably be best, but it is most often done with just reasonably thick one.

More info. HERE on bimmerforums.

2.3 Fitting non-BMW stock seats (VW, Ford Recaro etc.) :

To get the right height and a central-position with stock seats from non-BMWs there is a lot of modification to the mounts - these seats will always have the bolt-holes in the wrong place. The tidiest way would probably be to weld in rigid cross-beams like in the above guide [2.2], otherwise you will need to fabricate custom mounts. [I used a combination of wood-block and steel cross-beam to fit Ford RS Recaros to mine in THIS POST].

Check out my guide here: http://e21dub.blogspot.co.uk/2013/08/recaro-seat-base-adapter-finally-solved.html

3. Re-fitting stock E21 seats:

I have never seen anyone online do this. If you have level floor-mounts then I see no reason to switch back to E21 seats. All but the Recaros are uncomfortable, sprung nightmares. They give a truly bouncy and uncertain ride - only the most restoration mad would want it. The Recaros are super-rare and overpriced to fit the E21s mounts. E30 Recaros are a fraction of the price, have level mounts and are better anyway. If you are so desperate to restore your E21 dutifully, then I would consider it having cut floor-mounts a deal-breaker and to find one with stock seats, because the car will never be the same again.

There are 3 ways I see to achieve refitting stock seats:

1. Build custom outer mounts using a combination of the methods above, building them back up to the original and rather tall height for the stock seat-frames. [].

2. Locate a pair of original outer floor-mounts that have been cut out of another E21 and refit them to yours. These would first need to have been cut out carefully from the donor car and preserved by someone. Whether they would advertise them for sale is another matter, but asking on the forums can't hurt. Otherwise, you'll need to find someone with a scrap / breaking E21 and ask to neatly cut out its floor-mounts for a few quid. Either way, obtaining a useable pair is going to be tough.
Once you do though, they would just need to be measured up to where yours were cut off and welded into place. How neat a job you do will determine whether they fit or if it's unnoticeable.

3. Fabricate new outer mounts from the ground up out of steel and weld those in. I will endeavour to make a note of the dimensions of my cut one before passing it on and do a quick CAD design to fab-up a simple one.

**Also, I still have the passenger-side (N/S, Euro/US Driver-side) floor-mount [above], so if anyone wants it to try and weld back in message me! [Sadly, I cut the driver-side one out more severely and this is probably going to be the case if yours are chopped as it gives the wood or whatever more to grab on to.]

E21 316: Fitting E30 rear sport-seats - or having a go anyway.

Stock fit works, but leaves big gaps.

As with the front seats I used HSVTurbos build [here] as a rough guide. His rear bench-seat is the all-sponge kind, whereas mine have the sponge base, but a sprung back-rest, possibly due to the folding arm-rest or model year difference. This means I have a metal frame to work with on the back-rest, so it can be pressed flat to greatly reduce the proud fit at either corner, but also means more needs to be cut away than just blobs of sponge. The E30 coupe's rear seat-pan, the body-tub and front doors are almost identical dimensions to the E21, so the rear seat-base just slots in. There are no brackets along the bottom-edge to clamp the squab down, but with it seated flat and wedged under the back-rest these may not be necessary, although fabbing some up might be worthwhile to stop the carpet sagging down in the footwells.

The general shape of the back-rest is more or less the same as the E21 and the hooks fit into the existing brackets, though the E30's parcel-shelf is curvier, causing the back-rest to stick out slightly at the top corners. The back-rest also sits slightly higher, leaving an inch gap at the bottom between it and the squab. If these gaps don't bother you then the seat works fine like this and will only need a little chopping off each upper corner to achieve a pretty good looking fit. If they do, then a little more work is required to seat the back-rest flush and minimise the corner gaps.

The main problem here are the seat-belt reels, which protrude from the bulkhead and fill up where the upper corners of the back-rest want to be. The back-rest bolsters are also slightly too broad, though the centre of the rear frame is more or less a perfect fit to the E21 bulkhead.

Modifying the Back-rest:

1. Bend up the small hooks holding the cover material in place over each side edge of the back-rest and pull the fabric clear of the metal frame.

2. Cut away the side-support on each side of the frame, leaving just the edge of the 'mattress' frame that holds the springs, as in the photo below. The brackets at each bottom corner should come away here too.

3. Cut in half the metal bar that runs between the centre and bolsters, the one attached to the top spring in each corner, and trim away the top spring as close to the frame as possible.

4. Cut the metal bar running along the top of the frame about 4" in from either top corner

5. Cut away the boar-hair matting along each side of the back-rest to reduce its depth by about half.

6. Cut a 2" square from each top corner of the boar-hair matting to give a recess where the seat-belt can run freely back into its reel.

7. Replace the fabric cover, hooking it to points on the mattress-frame and tucking it under the springs. At each top corner, I pierced a hole and ran a cable-tie through to hold the folded fabric clear of the seat-belt reel.

Fitting to the E21:

To get the back-rest sitting flush to the seat-base the original mounting-brackets may have to be abandoned in favour of slotting the hooks on the bulkhead directly into the top of the back-rest frame. The original lower brackets are attached to the frame here and may need cutting off for a tight fit.

1. Hook the top lip of the back-rest frame over the metal hooks on the bulkhead. Press hard to make sure the metal bar gets over the hooks and not just the boar-hair and fabric. Give each side a good knock down onto the hooks. The top of the back-rest should be about 5mm lower than the parcel shelf.

2. Fit the centre arm-rest and lock the clips into place. The back-rest should sit a bit proud of the bulkhead and need pushing flat. Drill two holes through the back plate of the arm-rest and bulkhead. Fasten it together with two bolts or pop-rivets. Not only will this hold the seat in place, it will also stop it moving when the arm-rest is lowered.

E21 316: E30 Sports Seats - fitted.

MJNewbs from eBay got back in touch and we finally negotiated a low enough price for the seats. The fronts are in great nick, only a slight fray to the driver's back-rest, but the rear seat back-rest has a few tear that I'll address in a later post.

Thankfully, the E30 seat bases fit onto the inner stock mount, next to the trans. tunnel, on the E21 so they are already sited neatly in the centre and only require the outer mount to be lowered. Here's how I finally got them to an equal height.

The outer seat-mount was cut away about 1.5 inches height from the lowest point of the floor-pan and the top half completely removed from the sill. This leaves a large flat T-piece section onto which a length of '2by4' style wood-beam was placed that sits at the same height as the inner seat-mount, give or take 2mm.

To strengthen the edge of the wood where the seat sits a piece of 2mm-thick angle-steel was screwed in place, clamping the wood to the remaining edge of the cut seat-mount. The M10 seat bolts run through the wood and are bolted to the floor-pan, so the wood only acts as a riser, not an anchor and the angle-steel helps to distribute any downward force on the wood, or twisting motion as the seat is adjusted.

I chose to bolt my seats directly through the floor-pan for strength and this leaves a gap under the base of the wood at the inside corners, which I stacked out with a nut and large washers. This gives the added benefit of the seats being bolted first to the wood, then through the floor-pan with the same bolt. The downside is the sealed floor-pan nuts will need removing should the seat need to come out in future. The alternative method, used by HSVTurbo in his build here, is to bolt the seats to a thicker metal bracket, then bolt the bracket through the wood and floor-pan. This way the seat can be removed from inside the car leaving the wood fixed in place, but I just don't feel this setup will be strong enough, even with the thicker metal bracket.

I used M10 nyloc-nuts with a dab of stud-lock inside and large-diameter [40mm] 'bumper' washers. A good blob of silicone-sealant was put between the washer and body, then round the outside of the seated nut. Finally, I coated them in a thick layer of Finnegan's WAXOYL Underbody Sealant, for protection obviously, but also to blend the shiny nuts and washers into the car's underside.

I still have the rear-seats, including the folding arm-rest, along with the door-cards/handles and rear trim-panels, so we'll have to see how much will fit after the MOT.

E21 316: E30 Sports Seats vs. Re-covering the Recaros

Saw these absolutely divine Recaro sports-seats from an early E30 Baur cabriolet on eBay. They're all but identical to the Recaro/sports-seats from the E21, but have different subframes for the E30, not that it would make any difference now I've started cutting out the stock mounts and the inner side of the E30 base fits perfectly to the inner-mount anyway, so would be a bit neater/stronger than my all-custom base. Only snag is, the price is a little more than I'm willing to pay as the rear seat and door-cards are included. I've got them down a bit, but I'm sticking to my upper limit and they're having none of it. 

It got me thinking, the shape isn't too different from the RS Turbo Recaros I have, it's just the colourful Ford fabric that doesn't suit, but there may be a way to create some ultra-cheap 'replicas'. I figure the stock E21 seats aren't worth much at all, so there may be enough decent fabric left on the two to re-cover the centre-sections of the Recaros in beige cloth. This leaves the bolsters/head-rest grey alcantara, which is where fabric spray-paint comes in, about a tenner a can off eBay, to make them dark-brown. I whipped the cover off one of my E21 seat to weigh it up and it does look possible. On the other hand it has the potential to mess up a great pair of Recaros that are worth quite a lot more still than I previously thought, as well as condemn a tatty but useable pair of E21 comfort-seats, which I could at the very least donate to someone. At the risk of the end product looking naff, I don't think it's worth the sacrifice.

** UPDATE - Another pair came up on eBay yesterday and guess what, the guy emailed back about the original set accepting my offer. The second pair are a bit dirtier and the back seat is wrecked, but the seller will come to about half the other offer, only thing is he wants collection and they're in Cardiff. It will cost me the difference to drive down there, plus a day spent sat in the car. To be worthwhile I'd have to get this second set for buttons, so I called up the original guy and bought the set above - they'll come Monday and I can use the rear bench. I'm glad this seat problem is finally put to bed as the MOT is a week on Saturday and I need perma-fixed seats!

E21 316: Recaro Seat-Base Adapter - Finally solved!

I'm all for keeping things so they can be converted back to stock later on, but fitting seats with the E21 base-mounts is a nightmare. Once you've overcome the different height on each side and the mounts being too far apart, the seat has to be set low enough to be able to drive the car. I've tried a couple of times and just can't deem a complex two-height setup safe enough to be permanent. The Planted adapters from this post are just too expensive - I don't have £300 to spend on brackets for seats I had lying around so, with regret, the outer [higher] mount has had to be cut out. Gleefully this has done the trick and the passenger seat is now mounted at the perfect height and slides back and forth like it's on ice, so with a nod to retaining originality, this is the first thing anyone wanting to fit sportier seats should do.

Ripping out both mounts gives a blank canvas to put any seat-frame in any position, but a bit more research taught me that the inner mounts by the trans. tunnel can be re-used when fitting upgraded BMW seats, - Recaros, E30 seats etc. - which is what I would fit in future ideally, so they stayed and the outer mount came out to reveal 5" strip of flat surface, the only bit in this area of the floor-pan. Given the choice I would use steel box-section here to raise the flat section up to the same height as the inner mount and do some welding, but I just cant find it anywhere locally in the right size. I got some immense inspiration off this thread on Bimmer-Forums - http://forums.bimmerforums.com/forum/showthread.php?1757170-E30-sport-seats-in-e21 - in particular this guy, who used a block of wood - http://forums.bimmerforums.com/forum/showthread.php?1584670-HSVTurbo-quot-Mac-quot-Build-Thread. Would had been considered originally with the Recaro project, but not ruled solid enough. HSVturbo showed it can work here though and I guess as long as the bracket is bolted well through the floor, the would should be plenty solid as a riser and won't twist about.

It transpired there was a 2x4 type beam leant up in the shed that was pretty much the exact height of the inner seat mount, so I chopped off a 55cm piece of it, to match the full length of the inner mount - I can see the extra PVC-pipe thing works for HSVturbo, but one piece has got to be more secure. I then ran a length of angle-steel from left to right at each end of the inner-mount and bolted it through the existing holes. The angle-steel also sits flush against the front and rear face of the mount and wood-block. Lastly, the angle-steel is bolted through the wood to the floor-pan. Now I have two cross-bars to bolt practically any seat onto, good enough to rival the Planted adapter, well not quite, but it's an inch lower, solid and cost a whopping £6.99 to make. The carpet even fits snugly back over it, with a few slits for the cross-bars to go through.

To mount the Recaro on the cross-bars the base-mounts needed removing entirely. These are held to the sliders some of the strongest rivets I've seen and needed grinding and chiselling out, but thankfully not enough to mess up the holes, which I re-used to mount it with short M4 bolts. For the seatbelt-buckle anchor I just used a short piece of angle-steel, but it will need replacing soon with either a right-angle bracket at least 2.5mm thick, or better still some stalk type buckles from an E30. Some E30 Recaros would go nice with those too...

E21: Custom Seat-Base vs. Planted Adapter

Had a go at fitting the passenger Recaro seat, this time using the Ford sub-frame and slider instead of the BMW one. The driver's seat I did last year has sunk into the BMW slider and won't adjust anymore, not to mention the seat is too high. OK, I've got used to it and it's holding for now, but bolting things on top of the E21 slider/base plain doesn't work, is ugly and will need improving before the MOT. Using box-section etc. that won't sag down is out too - my head would be pressed against the roof.

For this side I chopped the left side of the Ford subframe so it would fit on the floor against the original outer seat-mount. This mount is an over an inch higher than the inner mount next to the trans. tunnel and this just adds to the problem, as the mounts are too wide apart for most seats anyway, so simply raising one side is no good, you need cross-bars. Cutting the Ford sub-frame and bolting it through the floor-pan on the outer side is the only way I could see keeping this mount, so stock seats could be later refitted, and without it all being set too high. The inner mount is just the right height, so I reused the bolt-holes to mount a piece of angle-steel, which the seat then bolts on to about half an inch further out. To bolt on to the angle-steel, the base-mounts had to be ground and chiselled off to leave just the sliders on the right side, which was a right pain. The placement of the seat was now perfect, but the funny shape of the E21s belly-pan, bespoke Ford mounts and custom-made risers did not make for the strongest design. The seat felt solid to sit in, but once I'd moved it back and forth a few times I felt the left side mounts twist and the sliders jammed. You could now feel it moving around a bit, so without a safety pass this is another fail.

It seems that there is just no way to keep the stock mounts and be seated nicely, unless you have better tools and materials than us and can fabricate a very flat, snug fitting adapter plate, with feet on one side and a seatbelt bracket. Believe it or not, they exist, made by a company called Planted in the US, available from a few sites over there [http://www.stableenergies.com/Planted/products/393/] and eBay [http://www.ebay.co.uk/itm/Passenger-Seat-Bracket-for-MOMO-NRG-SPARCO-RECARO-BRIDE-BMW-E21-Series-1975-1979-/120994172571?pt=Motors_Car_Truck_Parts_Accessories&hash=item1c2bd08e9b], though pricey at £150, each!

They're very nicely finished in 3/16" thick steel, bolt straight into the existing mounts and have a series of oblong holes to drop most types of sport seat onto, Sparco, Bride, MOMO, NRG, Recaro are menioned, though you don't get sliders. I've seen one with sliders made by Corbeau [http://www.harrisonmotorsports.com/corbeau-seat-brackets.html] available through Demon Tweeks, again £150 and will likely need adapting to fit non-Corbeau seats. I've been weighing up buying these for the best part of a year, so to weigh up the pros and cons they're an easy straight fit and let you keep the stock base-mounts, but with sliders on top the seat still sits too high and the crazy £300 cost for the pair is getting into E21 Recaros territory, so really I think it's worth having one last go at a custom adapter.

E21 316: Recaro seat fitting, 1st attempt...

E21 316: Recaro seats and re-trim!

These weren't planned like, they just fell into my lap yesterday. A workmate has been after an old mini-moto quad-bike I have for his son's birthday present. Only thing is he's skint, but I ain't used the bike since last summer so agreed to swap it for these awesome Recaro bucket-seats. They're a little bit more modern than the E21 is, but similar to the Recaros in the 323i so they wouldn't look too out of place and they're in great nick. These are from an Escort RS Turbo though, so the centres are trimmed in naff Ford patterned velour and need something a bit more in keeping with the beige 316 interior. I bought the most tan looking alcantara type material I could find today and it's still turned out looking a bit orangey and bright. It was Sunday afternoon I guess and the seats look and feel good, but I may have to hold out on the colour.