How-to: Swivel seat adapter installation

A couple issues installing on 2017 comfort seats...

I had a couple issues getting them installed to my satisfaction on my 2017 with 'comfort' package seats. Here's my full experience.

Ordering...
I ordered the RIB seats through Travois thanks to Peter Thompson's excellent write up. After waiting for a bit longer than I had expected (a couple months since they were not stocked and still needed to be imported at the time I ordered them (Mar 2018), I contacted Brad whom I had ordered from at the BC office. He was very responsive, and due to an honest mix up on his side, he apologized and fixed it right away. The swivel bases arrived a few days later. When they did, I noticed the driver side lock handle was bent but they otherwise seem very solid and I don't think whatever happened to the handle in shipping damaged the swivel joint or bent either mounting plate. Total cost = $675 with shipping for both swivel seat bases.

Installing...
Not sure if other Metris models have this but there is a little stamped sheet metal plate with a U shape extension inset towards the seat center. I'll call this the "extra bit" for simplicity when referring to it from here on in. This extra bit is welded to the bottom of the factory seat rail track. See the photo so you know to what I'm referring.

There is a corresponding plastic channel (with a connected wire) mounted on the bottom of the seat. When the seat is scooted fully forward these two elements are lined up such that the extra bit is within the plastic channel. Anyone know what this is?

My guess is its something like a Hall effect sensor to report full seat forward seat position. Perhaps unused or perhaps to disable the passenger dashboard airbag when the seat is too close. What ever it is, its preventing a clean mating of the seat to the swivel base. There is actually a much longer inline plate under the rail on the opposite side too (toward van center) but that one has no protruding U shape or corresponding plastic channel under the seat.

Whatever it is, this extra bit keeps the seats sliding rails from sitting flush on the top plate of the swivel base

when you mount them and that is an issue (it is for a careful perfectionist like me). On the fixed factory based there is a depression in the top surface of the seat mounting base which that accommodates this piece.

The RIB swivel bases are flat plates and so there is no room for this extra bit, and when mating the parts, the extra bit causes an uneven teetering front to back on the door side (both seats).

I considered just mounting and wrenching it all down - but I didn't want to bend the rails or the extra bit.

I considered grinding the extra bit off with an angle grinder - but I didn't want to destroy any intended functionality. Even if it's unused today, someone in the future may want or need it, and I'm sure I'd pay a high price for whatever I'd need to buy from Mercedes to restore the seat to its original state. My goal with any mod to my van, is to be able to bring it back to factory state if desired whenever possible.

This issue was really pretty significant and I scratched my head for a day thinking what the best way forward was. I ultimately decided if the mounting of the seat rails from the factory is really only at four points (due to the seat base depression, then I should be fine to raise the seat a little more with a thick washer in order to clear the extra bit. So I bought 8 nice fat steal washers

and attached the passenger side swivel.

These washers add another 1/8th or so to the height, oh well. Thankfully there is plenty of headroom to start with.

Use and Experience...
I have had the same experience as folks have posted before as for how to maneuver them into position so I wont repeat it. Well worth the effort for the benefit here I feel. My head touches the headliner when positioned closer to the front windshield and facing the rear but I can adjust and eliminate.

I notice the seats are less solidly fixed in place than with the factory fixed base. For example, if there is no one in the passenger seat I can shake it and it bobbles for a second before settling. Also, when sitting in the seat I can wobble it around a bit. I am 6'3" and 220lbs so somethings gotta give. I can see that the movement is all coming from flexing/bending of the swivel plates around the center hole swivel joint which seems very solid. While they come close, I have not noticed any contact between the top and bottom plates with the movements I have described.

I also hear subtle creaking/rattling from the empty passenger seat when driving. Its the kind of sound you might hear if you have a little sand between two metal plates. I'm hoping the sound will go away after some driving and tightening a bit and maybe even padding the space under the odd curved plate I mentioned (which now just barely contacts the bottom plate). At any rate, I am certain I can overlook these sounds after I get used to them.

All in all I am pleased with the results and look forwards to taking advantage of the increased openness and space this modification will offer.