BMW E90 3-series Seat Swap

[Spktyr]

Recently I noticed this post on reddit:

https://www.reddit.com/r/4Runner/comments/8tom5a/bmw_e90_seats_in_the_3rd_gen/

It seems someone figured out how to put F30 (despite the title) BMW 3-series seats in the 3rd gen 4Runner. He had a further imgur gallery here:

https://imgur.com/gallery/2QVANCA

Looked simple enough. However, F30 seats are still expensive and hard to find in most junkyards; these are the 2014-present BMW 3-series. His initial thought that they were E90 seats was interesting and there's a lot more E90 seats available in good condition at reasonable cost at junkyards as of this writing - these are the 05-13 3-series and being older though recent are very common to find crashed in yards; the earlier E90s can even be found in uncrashed condition with failed engines or expensive failed electronics that sent them to the scrappers. As my front seats are trashed and not all that compatible with my back, I decided to look around and see if I could find some decent E90 seats; I scored this set of 2009 E92 (BMW 3 Series E90 Coupe) seats for cheap. These are the best seats available in the E90s, the power Sport seats with four way lumbar and seat heating; E90 seats are available in manual or power, regular or Sport (with additional bolstering and slide out thigh support), with or without seat heating and/or lumbar. These power Sport seats have adjustable bolsters, where you can adjust the width of the bolsters.


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They do need some cleaning but that should be simple enough.

More to come as I put these together with my truck; I'll try to do better documentation so others can follow along.

 

[thezentree]

Wait, those bolted in?! Uh, tag.

 

[Spktyr]

Wait, those bolted in?! Uh, tag.

Apparently the F30 seats bolt in if you elongate the original BMW mount holes, per that post's author. I'm going to try the prior generation BMW 3-series' seats as they are similar - they may be able to fit as well. We'll find out soon.

 

[Ryance39]

If they truly bolt right in, I’m doing this.
I was actually trying to figure out how to get e39 sports seats into my 4Runner but they are seeming too wide. F30 seats are great too.

 

[Spktyr]

If they truly bolt right in, I’m doing this.
I was actually trying to figure out how to get e39 sports seats into my 4Runner but they are seeming too wide. F30 seats are great too.

From some preliminary measurements I made, E38/39 sport seats will technically fit but it would be really close and you may get rubbing. Didn't go much further than that because I couldn't find any good E38/39 seats for less than stupid money to experiment with.

 

[Ryance39]

From some preliminary measurements I made, E38/39 sport seats will technically fit but it would be really close and you may get rubbing. Didn't go much further than that because I couldn't find any good E38/39 seats for less than stupid money to experiment with.

I pulled the passenger seat out of my e39 to test fit it. The seat rails were off about a half inch and the doors wouldn’t close unless you really slammed them shut.

I think they are generally too big, but damn if they aren’t my favorite seats in any car I’ve ever had.

 

[Spktyr]

I had found a great deal on some E60 sport + comfort seats, which I like better - but that ran into the problem that literally none of the functions of the seat, not even fore and aft adjustments, will work without the E60’s body computer. I could use an Arduino or something to run it, but that was a lot more effort than I wanted to put forth into just getting a seat into a truck. I may still buy one for an office chair or something.

 

[RunningForNow]

Following. My last car was an E90 with the sport option, and those seats are fantastically supportive and comfortable. Driving position and rhonomics is what I really miss about that car. The 3rd gen ergonomics leaves a lot to be desired, starting with the awkward angle of the stereo, which makes it hard to read, and will probably give you carpal tunnel if you’ve converted to a touchscreen HU.

Nice find and thank you for sharing!

 

[Spktyr]

I’m rather surprised that nobody here seems to have noticed it before I did.

My problem with the truck’s ergonomics (that aren’t due to the truck aging) are mostly constrained to the seating. The front seat upper side bolsters are too close together for me and the lumbar support is entirely in the wrong place for me. Even fully deflated, I get lower back pain after 90+ minutes of driving from that thing protruding into my back. Hence my need to do something about it.

 

[Spktyr]

After some thought and noticing I had some Pick-N-Pull credits/coupons that would be expiring soon, I decided I didn't want to chop up my original seats in case the E90 conversion didn't go well. Instead, I went to Pick-N-Pull and ripped some cloth manual SR5 seats out of a dead 4Runner to serve as bracket donors.


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I also found a dead Limited and I harvested the power seat wiring connectors from it with the idea of making the swap as plug and play as possible - this would mean that if I found other E90 or even F30 seats I liked better later, it would be a matter of just unbolting and rebolting things as much as possible. One possibly disturbing thing I noticed on this Limited was that the driver's side harness connector looked like it not only had gotten scunge on it but that it had scorched and slightly melted - indicating that either it had been used for a prolonged amount of time or that the connection had gotten dirty and there was a lot of resistance generating heat. The passenger side (which would be far less used) was pretty much pristine. I'm going to have to see what my connectors look like when I pull my stock seat out.


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[Spktyr]

One issue the Reddit poster ran into was that the F30 adjustment controls would go comatose/turn off after a certain amount of time and he couldn't figure out why. The E90 power seats will do the same thing - I did some digging and found that E90 seats had been used as retrofits in other cars as well as in E90s that shipped with manual seats and therefore didn't have the wiring for the power seat and this issue had already been solved. The reason for the seat controls going unresponsive is that the seat controls are actually connected to a computerized control box *in the seat*. This computer is normally networked to the rest of the car using the now ubiquitous CANBUS system; when power is initially applied to the seat, i.e., when you turn the car on, the seat controller operates in independent mode while the rest of the car boots up. After a while, if it doesn't see the CANBUS network, the computer essentially shrugs and takes a nap. Simply cycling power to the seat will wake it back up. The permanent solution to this is to either provide a carrier signal in the form of switched +5V up to about 3 amps (plus a ground) to the appropriate terminals on the seat connector.

A more interesting element is that if properly hooked up, you *can* get the seat memory to work as the computer for that on the E90 is actually part of the on-seat control box - yes, that means that you and your spouse/significant other can have your seat positions saved and switch between them without spending ten minutes resetting the seat.

More reading, diagrams, etc., at the below links. I'll be including directions and pictures of how I hooked mine up but just in case something happens, here's the info I used:

https://www.e90post.com/forums/showthread.php?t=480313

https://www.pro-touring.com/threads/124866-BMW-E90-E92-E93-front-seat-wiring

Please be advised that there's at least one break point where the wiring scheme changed on the E90s and that you should always check the wiring for the specific year and variant of your donor to make sure you're not about to do something silly like detonate the airbag by hooking up power to the wrong spot.

 

[jgue467]

Now if only my 06's 330ci seats were actually comfortable and supportive (they have no give), I might try that! :cowboy:

 

[Spktyr]

Now if only my 06's 330ci seats were actually comfortable and supportive (they have no give), I might try that! :cowboy:

Which seat option do you have in that 330ci? The standard seats or the sport seats? I find the standard seats to be meh at best, but the sport seats are fantastic IMHO.

 

[S1996R]

Following, mine are trashed. Found some inexpensive seats in my area. I will see how it goes for you.

 

[sleepydad]

One issue the Reddit poster ran into was that the F30...

yea I remember seeing this on reddit.

https://www.reddit.com/r/4Runner/comments/8tom5a/bmw_e90_seats_in_the_3rd_gen/

https://imgur.com/gallery/2QVANCA

the reddit user

https://www.reddit.com/user/thisscharmingman

is on most days so... PM that user... I think I also remember seeing somebody trying to sell relocation brackets for these seats on reddit as well.

 

[jgue467]

Which seat option do you have in that 330ci? The standard seats or the sport seats? I find the standard seats to be meh at best, but the sport seats are fantastic IMHO.

Sport - they leather is in great condition, it's just that there is no cushioning compared to my 4runners cushion, the ride of course is superb on the bmw as opposed to the runner, errrr......

 

[Spktyr]

Sport - they leather is in great condition, it's just that there is no cushioning compared to my 4runners cushion, the ride of course is superb on the bmw as opposed to the runner, errrr......

Weird, I find the 4Runner seats don't have enough cushioning in the right places and too much in the wrong places. The lumbar support stabbing me in the back is exceptionally irritating.

 

[jgue467]

Weird, I find the 4Runner seats don't have enough cushioning in the right places and too much in the wrong places. The lumbar support stabbing me in the back is exceptionally irritating.

I should have stated, I had my front seats re-done. New foam bottom/back with new pleather (about $700), ultra soft then firms up with weight. Perhaps I should do the same to the 330?

 

[Spktyr]

Wiring information I found, supplemented by my reply, on another thread:

The EWDs show that both '98 and '99 go through a three-pin connector under the seat, but not the same one. The power for the seats is a blue wire on Pin 1 and a ground is a white-black on Pin 3. Since the seat is the one with the extra wire just disregard it. I can't find what it goes to but it is not the power seat circuit. So the power seat circuit doesn't need it. Just connect blue to blue and white-black to white-black and ditch the connectors, or use any mating set of two-wire connectors you can find.

Surprised I missed this the first time.

Revisiting this in the course of doing research my BMW seat swap and figuring out the wiring for it.



Key Reminder And Seat Belt Warning

On the driver's seat that 'extra wire' (white with red stripe) at the seat connector is power to the seat belt buckle switch - the switch tells the car that you have your seatbelt on and that it can turn off the seatbelt light.

The 'extra' one on the passenger side (yellow with green stripe) is actually considerably more important. This wire provides power to the Occupant Detector Sensor (really a weight switch) and through that to the seat belt buckle switch and then to ground. The ODS tells the computer that someone is sitting in that seat and to activate the airbag. It *must* be wired up correctly or if you have a passenger and get into an accident the airbag will not deploy, perhaps depriving them of needed protection.

All of this grounds, as best I can tell, either through the power seat motors' ground wire or through the seat bolts into the body. Have to look into this further.

I am currently looking into how to hook up the BMW's seat occupancy sensor properly.

Its looking more like the E90 seats aren't quite so much of a bolt-in as the F30s were. May still be doable with just drilling a couple new holes in the rails, but I'm starting to lean more towards welding the brackets onto the rail. That said, it would likely be a simple task for a welder and therefore not terribly expensive.

One reason I'm thinking the above is that the E90 seats have ~1/2" (more likely 13mm) holes for bolts to hold the seats to the floors. The Toyota bracket holes are 5/16" or smaller once you've drilled out the rivets and spot welds - yes, I can confirm that the brackets are not only riveted but spot welded to the rails.


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One spot weld is visible as a circle above the reverse-stamped R on this bracket, above the partially drilled rivet.

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Another issue is that the 1/2" holes have a reinforcing surround as part of the rail that makes it a bit problematic on one side. It makes it a bit difficult to mount up the outside rear corner leg because the holes are inconveniently placed. This isn't helped by the fact that the brackets aren't mounted the same distance apart on the Toyota rails. The outside brackets are riveted on 13.25" hole centers and the inside brackets are on 14.25" hole centers:


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The 14.25" hole spacing is roughly the same as on the BMW rails, but the 13.25" spacing could be an issue as that puts it right in the middle of the BMW seat rail rack.

 

[Spktyr]

Nope.

Turns out E90 seats aren't direct bolt ups. As feared, the shorter bracket distance on one side of the Toyota's seat turned out to be incompatible with bolting up the brackets to the E90 rails. However, that doesn't mean they can't be used in the 4R, just that it takes a little more work.

The reason: As mentioned above, one side has brackets mounted on holes centered 14.25" apart, and that matches up well with the factory BMW mounting holes. Unfortunately, on the other side, the hole centers are 13.25" apart and that basically is incompatible with the BMW rails without making adapter brackets that would raise the seat up beyond where I want it. Here's why that's an issue.


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In the above picture, you can see the four shiny squares on the rails where the BMW seat is bolted into the car at the factory. These are reinforced with additional layers of sheet metal; the holes in those reinforcements/the rail are a nominal 12mm wide and 9.5mm deep. The green arrow points to the motor that moves the seat fore and aft on the rails, the red arrows are where the motor's output shafts (Bowden cables, actually) enter the rack and pinion drive on each rail. This means that there's a threaded shaft over the rail that is riveted to the rail near those mounting holes and blocking access to the rail from above in the area the shaft runs. You can see a detail of the riveted point in the below picture.


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Here's what's on the other side - the top red arrow points at the rivet and the bottom at the threaded shaft.


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The arrow here points at the threaded shaft.


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On the outside rail of the seat, the brackets bolt to the factory BMW holes just fine and will be in the correct position to mount into the truck.


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On the inside rail, it just isn't happening. Even if you bolt the brackets in using the holes that produce the shortest distance between the brackets, you are still over half an inch too far apart to get the thing to mount in the truck.


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And, because of that rivet on each end plus the rack it's holding on, there's no way to drill a hole to mount the brackets closer together and still bolt everything down. So, it looks like if you're looking for an easy pure bolt-in solution with some hole wallowing you're going to have to use F30-series seats.

However, not all is lost. The rail spacing is fine, the rails themselves are nice and flat and the seat is self contained, still making them otherwise ideal swap candidates. I'll just have the Toyota brackets welded to the BMW rails. This project will be proceeding.