Adding suspension seats

The stock seats are fine for a delivery truck, but if you are driving across the country they are not the most comfortable place to park your butt. We decided to upgrade using a third party option. 

Knoedler Extreme Low Rider seats

We replaced the stock seats with some Knoedler Extreme Low Rider suspension seats. It was cheaper to do this than to buy the (unobtainable) Mercedes suspension seat bases and heater elements as aftermarket parts, and the result is much more comfortable.

When we ordered our van, we specified heated suspension seats. It added $1250 to the cost. The dealer sold that van to somebody else. The van we ended up with has neither heat nor suspension. Mercedes has stopped offering the suspension seat option while they work out how to integrate it with in-seat airbags, which all new models now have. The OEM suspension seat bases are expensive to buy on their own (about $1250 each) and permanently out of stock. Adding OEM heat pads after the fact costs $320 per seat, plus the cost of installing them in existing seat cushions, and of wiring them to the dash.

Knoedler make aftermarket seats for truck drivers. You can even order one from them with heating, cooling, and massage built in. Their suspension seats use compressed air for all the adjustments rather than a static air shock, like the Mercedes OEM version.

Knoedler have created a very low-profile suspension system that works in Sprinter vans. Their Extreme Low Rider seat has pretty much the same adjustment range up and down as the stock non-suspension seat on the regular height seat base.

The seats rest on a metal plate that is drilled for the Sprinter pedestal base. We found that the holes lined up just how they should.

We also wanted swivels on the seats, so that we can point them toward the back of the van when we’re stopped. Doing this gives us much more living area. Knoedler have two seat base options, one for direct mounting to the pedestal and another with some additional channels welded to it so that it is raised up above the swivel mechanism. That’s the one we chose.

CTA swivel installed on passenger seat base

We used the CTA brand swivels from Italy. They are imported by swivelsrus.com. We wrote about them already, but it’s worth noting that the Knoedler seat base interferes with the raised lip on the CTA swivel which holds the red release clip. We ended up installing the CTA swivels rotated 90 degrees so the release clip is on the door side rather than the front edge of the seat. We also ground out a small amount of metal from the edge of the Knoedler seat base to allow the top of the swivel to clear. I imagine it would be possible to bend the CTA lip away from the seat base, but I didn’t want to do anything that might make the swivel out of true.

The downside of mounting the swivel in this position is that it *might* be less secure in an accident. I don’t know. The bases should be designed to resist side impacts as well as front impacts, and they’re bolted to some pretty serious metal above and below, so I’m happy with this solution. The benefit is that the CTA swivels are designed with a front/back offset. Mounting them “sideways” means that the offset is now left/right. When you swivel the seats through 180 degrees, the seats end up a couple of inches closer to the center line of the van so they clear the B pillar better. That means you can swivel them with the door closed.

We mounted the passenger and driver seats on swivels, but had to take the driver seat swivel out again. The seat is too high with the swivel in place. We’ll decide later whether to buy the lower seat console (also called a plinth or base) or just not use the swivel on that seat. Swapping out the seat base will mean messing with the electrical components under the driver’s seat. Not an insurmountable problem, but not one we really want to have to deal with.

Getting the seats mounted in the van was pretty easy, but getting them hooked up with air and power took a lot more planning. You can specify a 12v air compressor with the seats, but that seemed crazy to us because we had already installed a compressor. Of course, that’s mounted at the back of the van. Getting a line all the way from the back to the front and finding a sensible place to route it inside the vehicle was not the easiest task in the world. One bonus extra from this exercise though is that we now have a quick connect outlet on the passenger side of the vehicle as well as at the back doors.

Air at passenger seat base. Not drilled through the seat base yet in case we change the configuration later.

There are power sources right underneath the driver’s seat, so adding the seat heat power was easier, but we still had to connect a fuse, and then run a line across to the passenger seat base through the plastic channel between the seats. We have the auxiliary battery, so we attached a Blue Sea 6-circuit fuse panel to that with an 80-amp Stinger relay so that it’s only energized when the van’s ignition is turned on. The heated seats could quickly drain the aux battery if that relay wasn’t there.

Blue Sea 6-fuse block

We took a chance and ordered the Knoedler seats with two arm rests. The stock seats only have an arm rest on the inside. If they put one on the outside, it would interfere with the B pillar and maybe with the door. It’s always been frustrating to us because the door is too far away to lean on comfortably and the door moulding is the wrong height to rest an elbow on. The Knoedler arm does not interfere. The seat does not slide far enough back for the arm rest to hit the B pillar, and it’s above the area of the door handle that would be likely to hit it, even on the driver’s seat without the swivel.

Like with all swivel seats in a Sprinter, our feet dangle when the seat is turned to the back of the van. That’s just because of the floor height difference. It might not be such a problem with lower seat bases.

Update: After driving the van on a longer trip (~1000 miles) we have decided the lower seat bases are necessary. It’ll help us to get full travel from the suspension seats. Currently they are close to their lowest height, so they don’t move as much as they could. It will also return the passenger seat with the swivel on it to a more normal height. There is enough head room when you use the regular seat base, but the passenger ends up looking out through the top of the windscreen. That piece doesn’t get cleaned by the wiper blades so it can be harder to see through.

Update 2: We moved the lower (horizontal) part of the seats closer to the seat backs. They have two sets of fixing holes and come from the factory with the seat cushions in the longer position. For someone 5’4″ tall, that made the cushions push too much behind the knees. Moving them back to the other set of fixing holes got rid of the issue. It’s nice to have that level of adjustment.

Update 3: We put the lower bases in, and everything worked out fine. Swivel on the passenger seat, none on the driver seat. The arm rests still don’t hit the door at the positions we use the seats in. The seats are at the correct height now. Note: we ordered the Knoedler seats with 4″ of travel (up from the default 3″). That might make a difference.

Resources

  • Knoedler don’t sell direct. We used seat-specialists.com to place our order. They were knowledgeable, patient as we asked questions in email, and gave us a discount on the list price. I’d recommend them.
  • Bostrom seats are an alternative to the Knoedler. Sold by several companies including seat-specialists. We wanted leather seats, so it wasn’t an option for us.
  • We looked at many types of swivels. There is a massive and still unresolved conversation about swivels on the Sprinter-Source forum.
    • Eurocampers sell German Sportscraft swivels for $250+shipping. These have an off-center swivel, so theoretically you don’t have to open the door to turn the seat around. People have complained that the rollers these use don’t turn properly and wear out, creating a rocking motion. Eurocampers claim they now use a different plastic for the rollers.
    • Sprinter Accessories sell European CTA swivels for around $300+shipping. These have a bigger hole in the middle to run wires through. You can get them much cheaper in Europe, but the shipping and duty might negate that saving.
  • Shorter seat consoles (plinths, bases). The Mercedes parts are A9069107300 and A9069107900 and cost $200 and $150 aftermarket. FASP also make a shorter seat plinth which seems to be mid-way between the full height and OEM short height plinths, but that’s only available in Europe. Some daring souls on the Sprinter-source forum have cut and welded their original plinths to be a lower height. Here’s a good write-up with pictures showing how one forum member swapped regular height bases for lower ones.

10 Replies to “Adding suspension seats”

  1. Hello – Great information about your entire Sprinter build….so much valuable information and I will be referring to your site the entire way during my build…..THANK YOU! I have a question regarding your “crew” bench seat. It appears that you moved it back to the furthest position…..I have read on the Sprinter forum about how to do so. Because I also have the Crew model, I understand that the mounting nuts are located under the floor from the factory. So locating them and drilling them out is the biggest hurdle. Do you have any write ups on this topic? Your explanations are done so well in all of your build topics and thought hearing it from you would be added reassurance! Thanks, Adam

    1. Adam, thanks for your faith in us!

      The thread on the Sprinter forum is about as good as it gets, although you have to read the whole thing. The holes are 858mm apart in every position, not just the first position like it initially says on the forum. We did do a write-up and you can find it here.

  2. Hi, we met at cyclocross last year and I know you are local is there anyway we can connect? I would love to take a look at your seats. I am in the middle of a 4000 mile road trip and it has become clear that the stock seats have to go. I was looking at the extreme low rider seats and then found your post.

  3. Thank you for your great post.
    I am about to buy the Knoedler extreme LR driver seat.

    I am 6,2 and 230# with the lower seat base from mercedes would a 7 inch travel a 5.5 inch or a 4 inch travel fit me better ?
    I like sitting higher but will i have enough room between my knee/thigh and the steering wheel ?

    What’s your recommendation ?

    John

    1. John, I’m reluctant to make a recommendation for you based on how different your height is to either of us. I’ll give it a go, though!

      If you’re used to the upright position you get in a Sprinter, then with the lower bases you’d probably be fine with a 4″ or 5.5″ travel seat. 7″ sounds excessive. Travel makes a difference to where the “sweet spot” is in the height adjustment. With less travel, you can run the seat lower and still have good suspension action. With more travel, the seat has to be higher to get the most benefit from the suspension. That doesn’t mean the suspension won’t work when the seat is lower or higher, just that you don’t get the same level of cushioning.

      Fore/aft adjustment is something that I’ve heard tall people complain about in the Sprinter even with the stock seat. I think some of that might be to do with people trying to sit “under” the steering wheel rather than “behind” it, if that makes sense. Treating the vehicle seat setup more like a truck than a car helps. Remember you can adjust the steering wheel height somewhat too.

      Basically, if you can make the stock seat position work for you then the Knoedler should be no different. What does happen though is that the seat raises up when you aren’t sitting on it, so when you first get in to the van, it might be harder to slide your legs under the steering wheel. As soon as you plunk your butt down on the seat though, that problem disappears.

      Will you be getting the built-in compressor? I’ve not used it, so I don’t know how it compares to our air compressor, but it would have made installation much, much easier if we’d bought that option. If you don’t need on-board air for any other reason, I’d probably pay for the built-in compressor option.

      1. Thank u.
        Yes I go with built-in.

        Knoedler just told me they will send me a bracket to adjust the travel to 5.5 inch if I wish to do that.

        Just FYI I got a 2016 model with thorax airbag!! but managed to find a company (they deal with seat conversions for handicap persons) who will place a resistor in the line so the computer will be tricked.

        1. The air bag thing is pretty simple – just a ~3 Ohm resistor in the connector for the airbag. I’ve been meaning to write about that for a while now.

          I’m glad you can get the adjustment bracket. I don’t think that was available when we bought our seats.

          1. I also learnt that there is a $1,000 possible rebate from MB if you replacing your factory bucket seats 6 mo from the date of purchase for those who qualify
            See below

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