Mercedes-Benz Ponton
Seat Belt Installation Guide II

This explains how I installed retractable lap seat belts with an attached shoulder harness in my 1959 Type 220S sedan. My apologies for the lack of photos, but my part time helper left my digital camera out over night in a pounding thunderstorm. Not to worry. He will be okay after he pays for the repair. When the camera comes back from the repair shop, I will take some photos of the various end products and update the page.

Project Rule #1: Since projects always take longer than you expect, multiply the logical number by 2.5.
Project Rule #2: Projects always take longer than you expect, even if you invoke Rule #1.

Based on my measurements, and a discussion with Andover Restraints (see Links), I ordered part #WS06F from them.

This is the bucket seat tan retractable lap/shoulder harness (2 ½" offset) for cars without OEM belts. The belts come with the short belt in the hard plastic sleeve (see Links). The kit arrives with 7/16" Grade 8 hardware. I also ordered some of the welded nut backer plates, but these turned out to be unnecessary.

I will tackle this procedure in four parts: measurements, and three mount points.

Day 1 / Measurements

Measurements are fairly easy. Simply print out the instructions from Andover (see Links) applicable to the belt style you have chosen. You can do it alone, but having a helper is nice. You need to measure your shoulder height in relation to the pillar and a few other items. I came up with the combination shown above.

Mount Point 1

The installation portion that I thought would be most difficult turned out to be the easiest. Remove the pillar cover by removing the four trim screws. I started with the top of the pillar. Under the cover, you will find a steel tab about ½" wide by 3" tall. This tab must be removed to mount your top bracket. It is spot welded in place, top and bottom. I used a Dremel cutting wheel on a flex shaft to take the bottom weld, then worked the top weld by rocking the plate. Once the tab is off, you will find two holes in the pillar panel (serving the threaded holes in the tab). These holes are convenient markers for the cutting that must be done. More about this in a moment.

Based on the comments of another Ponton group member, my intent was to slot the pillar at the point of the tab and mount the top bracket there. Instead of caulking or gluing the nut and washer in place, I decided to make my own welded backing plates. I took the supplied nut and tack welded it to one of the supplied flat washers. This combo was then welded to a thick flat washer intended for 5/8 or 9/16 bolt. I set this aside.

Starting ½" above of the baseline of the removed tab, I cut a vertical slot to about an inch above the top trim screw hole. This slot is slightly wider than the 7/16 mounting bolt. In retrospect, this slot should be at least the full height of the homemade backing plate. I corrected this on the passenger side the next day. From the top of that slot to the bottom of the upper stock hole, I widened the slot to the edges of the interior of the door pillar. The pillar is fairly narrow, not much more than an inch. What you should have is a gravity style mounting slot that allows the backing plate to drop into place and be retained by the remaining steel at the edges of the lower slot. All cutting was done with a Dremel cutting wheel on a flex shaft. I didn't use more aggressive tools for fear of slipping and screwing up the headliner, upholstery or myself. As it was, I still got some steel chips in one eye, in spite of the safety glasses. I washed out my eye and switched to a full face shield.

The backing plate will not fit, as is. I placed the bracket against the pillar and marked the excess. This was ground off to produce a "rectangle" with rounded top and bottom. Insert the bolt into the plate and check your fit in the slot. It should slide right into the upper slot and drop snugly into place in the lower slot. Once I am done with the fitting process, I will come back and weld the plate permanently in place. I may also bead the removed upper slot piece back in place for added strength.

It is also my intent to strengthen this mounting location by "sandwiching" the pillar steel between the plate and some washers. As far as I can see, I will place two thick washers between the pillar exterior and the trim plate interior. These washers will be as big around as will fit under the trim panel. This should allow be to seriously compress the plate into place and strengthen the pillar point. Due to the circular stamped section around the trim screw hole, I will have to grind the washers to conform to that curve so I don't wreck the trim panel.

Mount Point 2

Next, I mounted the female buckle ends (hey you, get your mind out of the gutter!). Due to the oddities of the Ponton, I was forced to depart from the instructions at this point. I had intended to mount the short ends to the propeller shaft hump (I thought I told you to quit thinking about that). Problem one is that the curvature of the hump really does not offer any decent mounting point. Problem two is that the hard plastic sleeve supplied by Andover is not quite right in the angle it forces the belt to if installed as directed. Problem three was more than I felt like dealing with. I crawled under the car to check my propeller shaft clearances. Boy, was I surprised. Totally enclosed. No easy way to get in there to place the Andover backer plates. So, back to the drawing board. Upon careful examination, there is really no place to mount the inner buckle ends to the floor. I suppose I could order longer pieces and slap them on the flat floor behind the seat, but they come only in black. Not a good look. I finally settled on the raised seat frame supports.

On the driver side, the vertical surface has several penetrations. From the rear, the first is square, with the next two round. I chose the round opening nearest the rear. Using a drill, I egged the hole upward to allow the steel belt end to fit flush. I purchased shorter bolts from the hardware store. I drilled a matching hole in the passenger side surface. At this point, I found that I had to bend the belt end plates to a 90 degree angle to allow the seats to slide freely. I put them into a vice and pulled them over with vice grips. This location also forces you to discard the rigid plastic belt cover. The frames have round access holes that will allow you to thread the bolts through. Even so, I found that I had to insert the bolt from the "inside" and the nut on the outside. My fingers are too big to thread the nut inside. Also note that I used thick flat washers on both sides to reinforce the mounting point.

Mount Point 3

The final mount I tried is the retractor. This unit must be vertical and unimpeded. Ideally, it should be directly below the upper mount on the pillar. As with the inner belts, the floor of the Ponton offers no practical mounting point in the flat floor areas. I finally settled on the door sill slightly forward of the pillar, with the retractor as close to the door and pillar as possible without touching. It turns out to be a decent location in that it does not impede anything and is not unsightly. My one aversion to this location has to do with the vehicle structure. This location forces one to put the bolt through the outer support rail running front to back. I do not like drilling into this on general principal, although it will provide a very solid mount. I am also worried about allowing water up into those rails. I will thoroughly seal the bottom when complete.

The one complication to this site is the depth of the rail. It is nearly six inches, longer than the average drill bit. Of course, I did not figure that out until *after* I got back from the hardware store. This trip was to pick up 6" long bolts. Well, they do not have 6" in fine thread and they do not have them in 7/16. That means I can not use the Andover backing plates here either. Harrumph. That was $50 out the window (I used POR-15 on them to reduce rust, so I could not return them). I picked up the 6" bolts and nylock nuts. I am not sure the 6" will be long enough, but the next size up is 8" at twice the price. We will see tomorrow. I have to go back and get a longer drill bit.

When the camera comes back from the repair shop, I will take some photos of the various end products. If I have time, I will pull the trim panel off and photograph the slot.

Day 2

Not too bad, with the knowledge gained yesterday. I popped down to the store and picked up a 12" drill bit. Once the holes were through, I placed the retractor in the previously mentioned location. The only problem I encountered was minor. The bolts I needed come in 6" and 8" lengths, but not 7." The 6" gives you just enough thread to get the nut on. You must crank it down, then back it off and place the washer. Then you can crank it down again. The "L" brackets used to mount the retractor are semi-concealed. I peeled back the door sill carpet to place the brackets. I cut a slit right at the 90° angle so the horizontal surface and the bolt is hidden beneath the carpet. The vertical surface of the bracket sticks up through the carpet slit, but is fairly well hidden by the retractor itself.

Final Thoughts

All in all, the job was not too bad, but most parts did not install where I originally envisioned them. I believe that I will go ahead and order the longer female buckle ends. I just do not like the idea of the belt secured to the seat frame, regardless of how well it is reinforced. This, plus the geometry of having the belt mounted behind instead of to the side has cemented this decision. In the meantime, I do have functional seat belts now. Big sigh of relief. Driving without seat belts is terrifying. I have seen too many accidents to feel otherwise. The retractors work very well and the belts are excellent quality. The cosmetics are also decent. I would not let that drive the project, but it is nice to have them look good.

Andy Litkowiak / October 4, 2002
Last Update: March 27, 2020
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