Note: I didn't do this because I was cheap... (archive)

I got part numbers, diagrams, a quote and talked with the service manager about getting this done to my car. But if you saw what I saw, you'd question how this is all put together at the dealership.

1)BMW's tether kit is only made for the 2000 and later models. These model years E39's have a threaded nut welded to the underside of the sheetmetal deck. On 1999 and earlier models, there only exists a 3/4" dia hole opening-no threaded nut available to screw mount the bracket onto. This is the major hurdle that I had addressed. BMW doesn't have a solution at this point. They only have parts to adapt to the y2k models.

ANyone who's retrofitted BMW's tether kit onto a 96-99 model therefore did so by either adapting the 3/4" hole opening onto the bracket, or had a new hole drilled (randomly I'm sure) and then bolt up the anchor bracket onto. The 3/4"hole opening that is in place on 96-99 models is the exact midpoint of the seating position, therefore any OTHER location to bolt the anchor bracket is going to pull the tether strap off center.

2) BMW provides as an anchor bracket, a Z-shaped 1.o" wide 19 gauge cold rolled steel sheetmetal part(0.047"thick). It has one(or two?) dimples stamped on the footing to fit through the prepunched hole(s) on the Y2K E39 sheetmetal shelf. It serves to restrict the anchor bracket from swiveling around the mounting bolt when screwing down the anchor bracket. It doesn't serve any other safety intent.

My selection for an anchor bracket is 1.5"wide, C-shaped, 0.25" thick hardened steel plate. There's over 200% more surface area contacting the sheetmetal shelf, and roughly 2000% more rigid than the stamped sheetmetal component by BMW.

3)BMW provides a 10mm bolt(approx.3/16") for bolting down the 19 ga. bracket.

My selection is a 3/8" diameter grade 5 hex bolt, twice the diameter.

4)BMW relies on the weldment around a 5/16" diameter metal threaded sleeve to contain the anchor bracket and to restrict any buckling from under the sheetmetal shelf.

I selected a 2" diameter, 11 gauge (0.097" thick) fender washer to mate around the underside of the sheetmetal shelf, and then reinforced it with subsequently smaller sized washers to clamp down the 1/4" conduit bracket. The surface area increased to distribute the load and restrict buckling is on the order of 6:1 of BMW's.

THe only thing I cannot duplicate is the fancy matching cover that conceals the top surface of the bracket. I guess I'll have to live without it.

Follow Ups:

You did your homework rr 01:50 1/22/2001 (2)
- Re: hole & predrill DHoang 08:15 1/22/2001 (1)
  - Re: hole & predrill rr 17:08 1/22/2001 (0)

[ Follow Ups ] [ 5-series (E39) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.