Seat Adjustment

[Reguam]

The one adjustment I had to make almost immediately is to trim the back support piece held by three screws under the seat. I have lower back arthritis and it was hitting it dead on. I took it to an upholstery person who has worked on another seat for me and he shaved about 1" off the top. It is not detectable by looking at it. I would like to go maybe a 1/2" more but at that point it may be too deformed. The trick is to keep the GT in the approximate center. An 80% improvement.

 

[wspollack]

The one adjustment I had to make almost immediately is to trim the back support piece held by three screws under the seat. I have lower back arthritis and it was hitting it dead on. I took it to an upholstery person who has worked on another seat for me and he shaved about 1" off the top. It is not detectable by looking at it. I would like to go maybe a 1/2" more but at that point it may be too deformed. The trick is to keep the GT in the approximate center. An 80% improvement.

Just curious: you have any before-and-after pics?

Almost three years ago, when I first got my '22 C 400 GT, I removed the butt bumper, just to check things out, in case I wanted to skooch back a bit. I was disappointed to find that the area behind it was very thin vinyl (or whatever), nowhere near as thick as the rest of the seat. Also, some of the plastic underseat partitioning edges seemed to poke through.

By contrast, I had two Burgman 650s, and removing the butt bumpers on those bikes revealed that the area behind them was covered in the same material as the rest of the seat, and with nothing protruding.

I gather -- at least, I think I gather -- that BMW has changed the seat of the newer C 400 GTs to make this better.

One other thing I don't understand: the C 400 X does not have a butt bumper, at least the three that I've ridden on Edelweiss tours (two in 2022 and one in 2023):



It seems to me that this an advantage that the X has vs. the GT (at least, in the pre-2025 versions of both bikes). It seems to me that this is a better trade-off, i.e., allowing the rider to slide back, on fully finished seat material, at the expense of not having that very-lowest-back-support device.

You make a good point about using local upholsterers. Back in 2010, I had an upholsterer work with me to add a custom backrest for my wife, along with some high-density foam, for the 2007 Burgman 650 I owned at the time:

 

[Reguam]

Yes, I do like the X seat better. And the overall looks. Not available US. I also had the 650 Burgman and just removed the butt bumper and was perfect. On the GT (2025 at least) the butt Bumper is covering a high solid bar under the seat which will break your spine on a bad bump. I did remove my BB while experimenting and just covered the three holes and bar with an Airhawk and this was perfect. Not at as attractive but still remains a last resort. It needs to be very secure because if it slips down past the bar it may not be notice. I will sacrifice looks for comfort. Not even a contest. I like to tour. They did reconfigure the seat for 2025 but hard to be specific about what they did. I will post an after picture but you may need to look for a stock before photo. I think the photos I already posted have the air hawk.

 

[Reguam]

Yes, I do like the X seat better. And the overall looks. Not available US. I also had the 650 Burgman and just removed the butt bumper and was perfect. On the GT (2025 at least) the butt Bumper is covering a high solid bar under the seat which will break your spine on a bad bump. I did remove my BB while experimenting and just covered the three holes and bar with an Airhawk and this was perfect. Not at as attractive but still remains a last resort. It needs to be very secure because if it slips down past the bar it may not be notice. I will sacrifice looks for comfort. Not even a contest. I like to tour. They did reconfigure the seat for 2025 but hard to be specific about what they did. I will post an after picture but you may need to look for a stock before photo. I think the photos I already posted have the air hawk.

 

[Reguam]

The 1" cut was noticeable but not good enough. I had an additional 1 1/4" cut making the total cut for the back point 2 1/4". All of it on the top. The guy did the touch up for free even though the 1st time he did what I asked. He said he could not go further and it was easy to understand why. The plastic insert gets wider or flares out toward the top so he left maybe a 1/4" of foam over that, so no where else to cut. I sat on it and it seems much better but as I discovered after the first time you need to take it out, especially on the freeway to know for sure. Today should be 70 so I will get out and see how it goes but I am optimistic.

 

[Reguam]

The 1" cut was noticeable but not good enough. I had an additional 1 1/4" cut making the total cut for the back point 2 1/4". All of it on the top. The guy did the touch up for free even though the 1st time he did what I asked. He said he could not go further and it was easy to understand why. The plastic insert gets wider or flares out toward the top so he left maybe a 1/4" of foam over that, so no where else to cut. I sat on it and it seems much better but as I discovered after the first time you need to take it out, especially on the freeway to know for sure. Today should be 70 so I will get out and see how it goes but I am optimistic.

The above process did not work for me because it left the remaining backrest too hard against my lower arthritic back. I took out too much padding because I did not know there was a protruding piece of hard plastic projecting off the back cover of the backrest making sort of a club pattern. Too hard with the backrest and too hard without the backrest in different ways. When the backrest is removed it is ugly, but also the seat without the backrest has a heavy piece of metal under the seat which is dangerous given a bad bump. What I needed was a seat like the X. I suspect the true intent of the backrest is to protect from the heavy metal bar right below the surface of the seat, but covered with the backrest. I suspect the X's design does not have the metal bar under the seat so does not need protection using a backrest.

I removed the back rest, and put a large AirHawk on top of the seat with the top resting right at the internal metal bar. I secured it with Alien Tape and can remove the bladder if I am leaving the bike for a long time. When I sit on the bike, because of how it is set up, the air compresses toward the back and covers the metal bar effectively, and offers some support. Not a bad fix and kind of huge because I was thinking maybe the bike had to go. Does not look bad at all. I miss not having the GT logo but the seat is comfortable.