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From digest.v6.n871 Fri Jul 11 10:00:42 1997
Date: Thu, 10 Jul 97 16:23:55 -0500
Subject: <E36 M3> Schroth Harness-Part 2 of 3

(Part 1 gave an overview and some conclusions. Parts 2 and 3 cover installation in considerable detail. Thanks again to the several people, and especially Duane Collie, whose input enabled me to do the installation and put together these instructions.- Neil)

Tools & Supplies

  • - Schroth Rallye 4 Harnesses, left and right sides
  • - E36 Harness adaptors
  • - Schroth shoulder pads (optional)
  • - Schroth grips (optional)
  • - 3/8" drive 16 mm socket
  • - 3/8" drive extensions
  • - 3/8" drive wobble extensions (optional but helpful)
  • - 3/8" drive ratchet handle
  • - 3/8" drive T40 and T50 Torx sockets
  • - Heavy-duty vise, sturdy enough to hammer on (essential!)
  • - Hammer
  • - Channel-Lock type pliers and/or Vise-Grips
  • - 5/16" washers, qty 4, for spacers
  • - Needle nose pliers
  • - Sharpie fine point permanent ink marker
  • - Eye protection (I'll explain why...)
  • - Towel
  • - Flashlight

Rear - Standard Method

Slide both seats forward and then release them to the rear seat entry position. Get in the back facing rearward, grasp the seat bottom at its front edge with both hands, about a foot inward from each side of the car. Tug sharply upward to unsnap the seat bottom; remove it from the car. Notice the airbag controller box and some other wiring under the seat: make sure you don't disturb any of it. With a ratchet handle, extension, and 16 mm socket, remove the inboard seat belt anchor bolts.

Pull back the grey foam rubber stuffing at the rear outer edge of the seat pan. The outer seat belt receptacle anchor bolts are partially or fully recessed under the outside trim panel edge, however this panel does not have to be removed. Instead, push the bottom edge of the trim panel hard outward to expose the bolt head, then push a 16 mm socket with a long extension over the bolt. Because these bolts are slightly angled outward you may find it useful to use a wobble extension. Unscrew the anchor bolt and remove the receptacle stalk. All the seat belt anchor belts are hard to turn and have a very fine thread. This will be important to remember when you replace them.

Lay out the tailstraps of the Schroth harness, make sure they are the right way up and not twisted. Both mounting brackets will have to be bent.

The outboard harness bracket will be mounted on top of the standard receptacle stalk bracket base, extending forward and then bent up at a right angle. Mark the inside of the bend line with a Sharpie, fairly close to the small end mounting hole. The bend position isn't very critical here, just leave room for the bolt head and drive socket. Clamp the small end of the harness bracket in a vise, grasp the other end and bend. Make sure the bend is in the right direction first. Use a hammer to tighten the bend if it curves too broadly.

The inboard harness bracket goes under the original seatbelt anchor bracket. It will point backward, then bend up at a right angle. Because it has to bend around the outside of the original bracket, the location of the bend you make is more important. It must be closer to the large end in order to clear the factory part. Mark the bracket with a Sharpie, clamp the small end in a vise, and bend. The bend will probably be more rounded than you want, use a hammer on the vise to make more of a right angle.

Now you are ready to bolt down the harness brackets. At the outboard side thread the bolt through the harness bracket first, then the receptacle base. Note that the receptacle base has a locating tab which goes into a hole in the car to orient it. Because of the angle of the bolt it can be difficult to start without cross-threading. And because these bolts are hard to turn anyway, it's also hard to tell if they are cross-threaded. Using the extension, try to hold the bolt orientation so that it is true to the hole as you start it in the threads, and fasten it down.

Make sure the tailstrap isn't twisted, and fasten down its inboard leg. This time the harness bracket goes under the factory anchor bracket. Repeat for the other side of the car. Replace the rear seat bottom after threading the harnesses over it. Push the rear edge of the seat all the way back, then snap down the front.

Rear - Alternate Methods

This normal installation results in a semi-permanent setup. However there is a rear crossmember under the parcel shelf which is already designed to withstand seat belt accident forces (the stock shoulder belts are in the folding seatbacks, which latch to this crossmember). There are three threaded bushings preinstalled in the crossmember. These are normally concealed under the parcel shelf covering, and are intended to secure child safety-seat retaining straps. It's not clear to me if these 8 mm bushings are sufficient for harness anchors. It would be possible to improvise some other form of attachment to the crossmember.

I have seen installations where eyebolts are bolted through holes made in the trunk floor. I've also heard of, but not seen, custom machined adaptors which connect a single harness tailstrap to each rear seat latch once the seats are folded.

I've envisaged adapting the harness tailstraps with stock seatbelt buckle tongues to snap into the rear seatbelt receptacles (the centre receptacle would carry two tailstraps). This would be quite easy to do, but requires resewing the harness ends, with potentially disturbing safety implications.

Installation of the front harnesses continues in a separate message.

Neil Maller
96 M3

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