[Prev][Next][Index][Thread]

E36 harness belts (instructions)

For all you fellow track junkies who want to install a harness belt system in
an E36, here is what I did in an E36 M3 WITHOUT a roll bar.  (I make no
representations about safety - if you don't have a roll bar in your car, no
harness system is going to save you in a rollover.)  This is for a 4-point
Schroth harness system for both front seats, so you may need to improvise if
you are installing a 3, 5, or 6-point system.  

Materials you will need:

2 harness belts (about $150 each for 4-point Schroth)
2 steel bars (plates) - 1/4 inch thick, 2 inches wide, about 19-20 inches
long (See step #1 below)
4 long 17 mm bolts (grade 10) (See step #1.d. below)
8 quick links - 5/16 inch size (about $2.00 each)
4 eyebolts (about $6.00 each)
"Harness bar" - optional (See step #5 below) (about $100)

Total cost with harness bar:  About $450-500 ($300-350 for just driver side) 

Instructions:  

1.  Fabricate two bars (plates) for the rear seat rails of the FRONT seat.

     a.  Measure the distance between the two bolts holding the seat rails
behind the front seat.  Mine was about 19.5 inches.

     b.  Cut the 1/4 inch thick by 2 inch wide steel bars (plates) to length
measured in step #1.  (I bought a 4-foot long bar and made two plates from
it.)

      c.  Loosen (you don't have to remove) the two front seat rail bolts (16
mm).  Then remove the two seat rail bolts behind the front seat (17 mm).

      d.  Take the 17 mm bolts to a BMW dealer and ask for the same hardness
(grade 10) bolts in a length about 1/4 to 1/2 longer than the original bolt.
 The dealer has these.  I'm not sure what they are normally used for.

      e.  Slide the bar between the seat rail and the floor (behind the seat)
and mark holes on the bar at the OEM bolt hole location.  Remove the bar and
mark another hole about 2-3 inches inward (toward the center of the bar) from
the first holes that you marked.  Drill all holes with a 1/2 drill bit.
 Install the steel bars between the seat rails and the floor behind the front
seat using the new longer 17 mm bolts.

2.    Purchase "quick links" (the kind that have the threaded ends and a nut
that closes the ring gap - NOT a snap link) in the 5/16 inch size (these can
be found at most hardware stores and are rated around 1500-1700 lbs. load).
 Install the quick links in the inner holes on the bar.  Attach the lap belt
parts of the harness system to the quick links.  Retighten the 16 mm bolts at
the front of the seat rails.

3.  Purchase eyebolts from one of the race supply vendors in the Roundel (I/O
Port Racing, etc.)  Remove the rear seat.  Replace the 4 OEM bolts that hold
the rear lap belts in place (the LOWER mounting points) with the eyebolts.
 The thread size is identical.  Use some lockwashers under the eyebolts.  The
eyebolts are longer than the OEM bolts, so you can leave the original seat
belts in place - just replace the bolt. 

4.  Connect quick links to the 4 eyebolts.  Connect the rear belt of the
harness system to the quick links.

5.  Now you have a choice of whether you want to have the harness run from
the top of the front seat down to the rear seat, or instead use a "harness
bar" to run the harness from the top of the front seat over the bar and then
down to the back seat.  The "harness bar" is a long bar that bolts between
the upper front seat belts mounting points on the B-pillars.  If you are
tall, the harness bar make the harness belt more comfortable because there is
less pressure on you shoulders from the harness.  You can get the harness bar
from many of the Roundel race supply vendors.  I got mine from I/O Port
Racing for about $100.

You now have a harness system that can be easily linked into place and then
removed after a track event.  You can leave the eyebolts in place (just
remove the rear belts and quick links).  The rear seat will fit back in place
over the eyebolts.  The bar under the rear seat rails of the front seats can
also be left in place if you don't mind the extra 1/4 inch raise in height
from the bar thickness.

One caveat --  on the M3, because of the seat adjustment hardware under the
front seats, when you have the bar in place under the seat rails, you will
have to RAISE the entire seat (middle lever) to its tallest height before
sliding the seat back and forth.  This allows the mechanisms under the seat
to clear the bar.

Hope this helps.  Keep the top side up!

Regards,
Bob Stommel
Indianapolis, Indiana
78 320iS, 88 M3, 95 M3