E46 M3 coupe seats into Z4

[JimCosworth]

Put some nice E46 M3 coupe seats into my E85 to replace the comfy but not too supportive standard seats. I was after a set of E85 m sports but after months of looking black ones never seem to drop the £400 mark which I couldn’t really justify.

I picked up a set of E46 fully electric (but not heated unfortunately) M3 coupe seats for a fraction of the cost E85 m sports. These have the electric adjustable lumber and side bolsters so you can make the bolsters tighter if you’re doing more spirited driving.

If anyone is interested I’ll do a walk through of what you need to do to fit them. They bolt straight up to thr E85 and the electrics use the same plug. Only thing you have to do if transfer the seatbelt mounting bracket over from the old seats and also use the E85 seatbelt pretensioners as the M3 cause a seatbelt warning light.

 

[RMB]

Good work, I’m surprised that they physically fit and that they’re cheap, unlike E46 M3’s now!
More pics welcome.

 

[JimCosworth]

I wish I’d taken more photos of the process but I didn’t but there are guides already on the internet which I used.

As a quick reference though:

If you’ve got electric seats it’s useful to do it in this order:

- Move the seats fully back to access the two 16mm nuts that mount the rails to the floor. Take these off.

- Move seats fully forward to take off the two 16mm bolts that mount the rear of the rears.

- Move the seats upwards which gives better access to the electrical connector.

- Disconnect the battery and wait. Some say ten mins some say thirty. I waited about 15 mins on average. This is to prevent any small risk of the airbags activating when you disconnect them.

- Reach under the seat from the front until you find the multi plug connector that slots into a yellow housing. You have to slide a black locking strip to the side using your fingers or a flat head screwdriver to allow you to withdraw the connector.

- unbolt the seatbelt from the anchor point on the bracket at the rear of the seat. I think it was a 17mm spanner you’ll need.

- withdraw the seat.

- You need to take the seatbelt anchor point bracket over to the M3 seat. I used an angle grinder on the circular captive ‘nut’ on the back to get it flush with the rail then drilled it out and used a punch to push the bracket free.

- I wanted to use M10 bolts so had to widen the hole in the bracket very slightly using a step bit. You also need to widen the mounting hole slightly in similar fashion on the new seat rail. You can then use an M10 bolt. I used a carbon steel bolt marked 8.8 which should be up to the job.

- Now you need to unplug the plug connector on the top of the seatbelt pre tensioner. You don’t need to take this wire over as the M3 has this in place but you do need the second wire which connectors to the main multiplug connector. You have to disconnect this wire that’s attached to the pre tensioner and take this over to the next seat. I think this is a sensor for the buckle and will produce an error if you don’t take it over.

- Swap over the seatbelt pre tensioner to the new seat.

Refitting is the reversal of removal but remember to use lock tight on the bolts.

If you don’t re-connect the battery with the seats out you shouldn’t get any errors but if you do you can’t use BMW scanner to clear the error for some reason. You will also get an error of 9891 seat belt buckle open circuit if you don’t use the E85 seatbelt tensioners. In this case you can use a creator C310 to clear the error.

Give me a shout if anyone needs a hand.

 

[r3vmatch]

Hi Jim,

I was thinking of getting some Corbeau seats but this caught my attention. Did the ride height / seat height change appreciably between the original Z4 seats and the E46 M3 ones? Also does this have any kind of adjustable lumbar support? That is my biggest complaint about the Z4 "M-Sport" seats.

 

[TriggerFish]

They look good! Do they impact how far back the seat goes? They look much thicker, so I'm suspecting they do?

 

[Beerman]

I'm already at the limit for tallness to drive a Z4.

Those seats must have a significant impact to driver height. They are much thicker and also won't retract into contour behind the seat.

 

[JimCosworth]

The seats don’t sit any higher than the old seats if you are swapping electric for electric. I did a lot of research and apparently manual variety of both seats sit very slightly lower but it’s not much and crucially M3 seats sit the same height as manual Z4 seats and likewise for both electric ones. Hence if you’re moving from manual to electric it would sit slightly higher but I’m told it’s not really noticeable. If moving from electric to electric it will be the same height.

The M3 seats do seem fractionally wider than the Z4 but go in fine. They fully recline all the way back. I’m 6’1 and there is plenty of leg room and they aren’t even all the way back.

I took it for a spin yesterday evening and the adjustable side bolsters are good. You press a button on the corner of the seat and they inflate and grip you much better than the standard seats.

The only disadvantage is my M3 seats aren’t heated but if you shop around you can get fully electric and heated ones but they aren’t cheap - the cheapest I’ve seen were around £360. I went for these as they were cheap. These are M3 coupe ones. The convertible ones are a slightly different style. They both have the M emblem in the headrest:



Also, a lot of the seats for sale are worn. Personally I would avoid anything with torn bolsters but a bit of greying where the leather is worn is easy to rectify. My driver’s seat has a worn bolster but a few mins of cleaning and adding some black leather dye and they look fine.

Before with some wear to the outer driver side bolsters:


After a clean and adding some dye to the bolster:

 

[JimCosworth]

I’ve just tried seeing how far the seats go back and they do go right back okay



These are the extra controls you get on the M3 seats for lumber and side bolster adjustments. Not seen these before but really impressed.


One other thing I didn’t mention is the coupe seats don’t have the seatbelt guide by the headrest. Not a massive problem but you have to reach back to pull out the seatbelt. I knocked up a crude but effective bracket for each side just to hold the seatbelt forward in an easy position to reach it. I’ll probably make up a metal guide at some point. You can also buy ready made brackets called ‘seatbelt butlers’ off eBay for about £40.

My homemade brackets:

 

[r3vmatch]

Love the "home grown seat belt" guide but as a suggestion maybe rotate it 90 deg and mount it to the back of the seat so there are no safety issues in the worst case of an accident!

 

[JimCosworth]

Love the "home grown seat belt" guide but as a suggestion maybe rotate it 90 deg and mount it to the back of the seat so there are no safety issues in the worst case of an accident!

Thanks, although I can’t really see what the danger would be.

These generic ones are on eBay but I’ve seen people say they can rotate as they are only fixed on one of the headrest uprights hence why I used both uprights for mine.

https://ebay.us/m/Qv9SIf

 

[RMB]

“These are M3 coupe ones. The convertible ones are a slightly different style. They both have the M emblem in the headrest:”

[ref]JimCosworth[/ref],

The E46 M3 vert seats were very different. They were the same as the standard 3 series verts in shape, but had nappa and the M.
Wider and less supportive with the seatbelt holder fitted holding the headrest.
They offered very little lateral support from memory.

 

[Mr Tidy]

I'm also surprised they fitted as they look so much bigger than Z4 seats, but the electric lumber support and M logo are a real bonus.

An even cheaper option may be E46 Compact seats as they already have a seat belt guide. My 325ti was a Sport so it had there M-Sport seats.