Racing seat installation in my BMW E36!

Lately, during my autocross runs, I’ve found myself sliding around in my seat during the hard cornering. I’ve had to brace my legs against the door and transmission tunnel. I’ve also been using my arms to keep in position when all they should be doing is steering (and a single shift). A snug fitting fixed back race seat would keep me locked in position, and shed a good amount a weight. Sounds like a win-win!

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As you can see, my stock seat has seen better days! The thing is an overbuilt beast with three electric motors for seat adjustment plus heating elements. The stock seat weighed in at 58lbs!

After doing quite a bit of research, I understood the type of seat that I wanted and the general dimensions that would fit in the car. I settled on a fixed back FRP (fiberglass reinforced polymer) seat design. A fixed back seat is stronger and lighter weight than a reclining style seat. Using a FRP design, as opposed to a tube frame, also brings lighter weight and the added benefit of being able to side mount the seat (as opposed to bottom mount). Side mounting a race seat allows the seat to be mounted as low as possible in the car and thus allows more room for a helmeted head.

SP2 Seat

I proceeded the search for the right seat on many different websites, for both new and used seats, to find one that met all my requirements while not blowing the budget. I’m not using this for endurance racing or to meet FIA standards so a $1000+ seat isn’t necessary. I finally settled on the SP2 seat from Sonic Motor. In my excitement to get my seat installed after receiving it I forgot to take proper pictures of it so you’ll just have to see the pictures above from the Sonic Motor website.

You can see that this is a fixed back FRP style seat with side mount brackets already installed from the factory (somewhat rare). The seat also came with sliders but to me that just added weight so I’m not using those. The seat weighed in at 24lbs (including the side mounts) so that’s quite the weight savings!

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Now to the issue of getting the seat safely mounted without spending more on mounts than the seat itself! You can buy specialized BMW E36 racing seat mounts that would fit a variety of seats (such as at VAC Motorsports) but they just looked like too much added weight and something I could probably make myself. After looking at how the stock seat was mounted, I devised a plan to use 1/4″ thick steel plates (both 1.5″ and 3″ wide) and grade 8 bolts/nuts purchased from Lowes. The plates ended up being 4.5lbs when cut to the proper size.

Seat Mounts in Car

In the picture above, you can see how I cut, mounted and drilled holes in the plates for the race seat side mounts. You can also see that the stock seat mount locations are spaced too far apart to simply mount the new seat in the same place, thus the need for the steel adapter plates. Luckily, the stock seat mount pedestals are rather large and flat across the top so both the front and rear plates sit level and are supported along enough of the span so that they don’t flex.

Seatbelt mounted to seat

The next step was to figure out how to mount the stock seat-belt receptacle to the new seat (I’m still using stock seatbelts at this time). I just wanted to reuse the stock receptacle as that looked to be both the safest and lowest cost solution. The stock BMW E36 seat belt receptacle is a “V” shape and contains a tensioning device  in the lower horizontal section. I was able to remove the entire thing from the stock seat by simply removing two specialized bolts. I then just drilled two appropriate holes in the SP2 seat side mounts and installed the receptacle with new grade 8 hardware. Easy and safe!

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Here’s the seat installed in the car. Just ignore the general lack of an interior for now as that’s a future blog post all in itself! The seating position is perfect for me. Both comfortable and correctly aligned with the steering wheel and pedals. It’s incredibly solidly mounted with absolutely no movement at all in any direction.

Though it wasn’t a drop-in replacement, getting a fixed back race seat installed has given me a superior driving foundation while removing nearly 30 lbs of weight from the E36. Well worth it!

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Stayed tuned to learn more about what the heck is going on in the interior of the car…

Vendor Links:

Sonic Motor SP2 Seat

VAC Motorsports Floor Mounts

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