[PoorInRichfield]

Even the inner tube solution isn't an ideal solution. Looking at pictures of other people's bikes with an inner tube hack in-place, the indentation on the back of the seat post makes a nice channel for water and dirt to run down into the frame and right past the inner tube. Hence, a good solution needs 2 parts:

1. Seal around top of seat tube that has a "fat section" that will fill the gap caused by the channel in the seat mast.
2. Cover for adjustment slot.

This person's bike actually has fenders on it as well, but the owner mentioned that water (and hence dirt) still gets in the frame when washing the bike.

 

[norcallincoln]

While I love my 2020 Domane SL7 Disc, I can't help but think that the seat post design is just begging for water and dirt to get into the frame. The binder bolt to tighten the seat post mast is a giant slot in the back of the seat tube which is a primo-place for overspray from the rear tire to go:

I think it would be nice if Trek devised a rubber "plug" for this hole to help keep water out, similar to the plug on the chain stay for the DuoTrap sensor:

Can you think of a way to seal that hole, but still allow access to it in the event that I need to remove or adjust my seat post?

I considered just putting some kind of tape over the whole, but obviously that would mean a new piece of tape each time I adjusted or removed the seat post, not to mention the build-up of tape residue.

I just bought a brand new domaine 6 etap. Today was my3rd ride and I noticed for the first time this uncovered slot for adjustment. After reading the thread here I will be going out and getting white electric tape to cover it. A design flaw indeed. Does trek expect people to ride in dust free, rain free conditions at all times?

 

[Toni_Maloni]

Hello everyone,
I just have the same problem with my TREK Domane SL5 (2022/23). Not only, that the seatpost has this huge gap.. it is also movable when sitting on it and paddling. The seapost moves from left to right and causes a really loud creaking sound! it is almost impossible to ride.
I guess you guys should have the same problem, as it is caused by the (bad) design??

Today I was at my Trek dealer and they could not fix the problem. They started to grease the whole seatpost and inner frame with carbon grease and screwed it together with 7 Nm.
But it did not fix the problem, the creaking noise was still there.

At home I analyzed the problem. In my opinion the real problem is, that the seatpost is moving in the frame! The notch on the seatpost and the edges of the frame should form-fit together. But they do not. I think the force on the seat is so high, that the form-fit connection can not hold it in place. The side effect of a moving seat is the wear on the seatpost and frame. This should be stopped in first place!

What I did to fix it, was to reduce the gap first.
No gap = no moving = no sound = no wear

I put a rubber band around the seatpost, so it closed the gap to the left and right side, or at least reduced it to a minimum.
Then to close the gap I used insulation band. This works really well.

You can see the result on the pictures. I take my bike out for a test ride now.
But it already feels more stable stays in place when pushing it.

Stay tuned!

 

[Toni_Maloni]

Update:

I took my bike on a test ride, with the thin rubber band between seatpost and inner frame.
The feeling was quite good. The movement of the seat was definitley less, no creaking sound!!

Back at home I did an upgrade 2.0 with a slightly thicker rubber band (around 1mm thick and 4mm wide - just a normal rubber band for office stuff, kitchen stuff).
As you can see the band is wide, and I had to wind it twice around the pipe but without overlaying the band. On the contact points the band is flat, the twisting is on the backside, where the seatpost has the clearance. I also put a lot of grease (just normal graease, without any friction additives) on the band to make the insertion smooth.

At the end I cleaned the outer surfaces with iso prop and put my insulation band on it to close everything.
Looks quite good and aero!

What do you think?
Also when pushing the seat, the is almost zero play! Feels really stable now!
No movement at all, no creaking sound, and no wear!

My resumee:
Definitley a practical way to reduce any movement/wear/sound on your seatpost.
But at the end, for a >3000$ bike, this should not be!!
TREK designers have to learn from this and do better next generation...

 

[Peter P.]

Congratulations on solving your problem!

Rubber bands don't last very long. I would recommend going to your local hardware store and buying a properly sized O-ring.
They come in many diameters and wall thicknesses, and don't deteriorate with age.
Also, if you stack a couple of them, you'll solve your water intrusion problem as well.

My framebuilder supplied a properly sized O-ring with the frame to seal the end of the seat collar. Worked so well I bought one for my other bike.

 

[Toni_Maloni]

Congratulations on solving your problem!

Rubber bands don't last very long. I would recommend going to your local hardware store and buying a properly sized O-ring.
They come in many diameters and wall thicknesses, and don't deteriorate with age.
Also, if you stack a couple of them, you'll solve your water intrusion problem as well.

My framebuilder supplied a properly sized O-ring with the frame to seal the end of the seat collar. Worked so well I bought one for my other bike.

View attachment 485094

Hello Peter,
yep an O-Ring would be a more "engineering" solution. Right.
It should be more sustainable, for sure.
I will keep my eyes open.

The thing is, the Domane seatpost is not a round pipe. It is D-shaped and has a notch on the backside.
That makes it impossible for an O-ring to seal it all round.

 

[velodog]

Hello Peter,
yep an O-Ring would be a more "engineering" solution. Right.
It should be more sustainable, for sure.
I will keep my eyes open.

The thing is, the Domane seatpost is not a round pipe. It is D-shaped and has a notch on the backside.
That makes it impossible for an O-ring to seal it all round.

A tight or snug fitting O-ring will conform to the shape of the seat post, same as a rubber band.

 

[Peter P.]

A tight or snug fitting O-ring will conform to the shape of the seat post, same as a rubber band.

Exactly. To prevent water infiltration at "the notch you speak of, fill it with grease and wipe off the excess.

That notch in the rear is also why the two custom frames I had build, including the one in the photo above, have the slot facing forward.
That way there's nothing that can get kicked up by the rear wheel which lands in the notch.

 

[siggs]

Hello Peter,
yep an O-Ring would be a more "engineering" solution. Right.
It should be more sustainable, for sure.
I will keep my eyes open.

The thing is, the Domane seatpost is not a round pipe. It is D-shaped and has a notch on the backside.
That makes it impossible for an O-ring to seal it all round.

MY god man that is a massive gap, I have to wonder why it is more than on my frame? I ended up with a replacement frameset and now after 9 months I am starting to feel some play in the post and seat tube. I opened it up today and wow wear on the post and tons of grit inside. What do I do to clean this out and is all that sand traveling down into my BB area? I have not even ridden it in the rain, only damp roads 3x , I do no see how this could be considered acceptable by trek.

 

[PoorInRichfield]

By the looks of the Gen 4 Domane, it appears as though the Trek engineers were paying attention to the shortcomings of the Gen 3 seat post design. Unfortunately, that doesn't help us Gen 3 owners.

 

[widda]

MY god man that is a massive gap, I have to wonder why it is more than on my frame? I ended up with a replacement frameset and now after 9 months I am starting to feel some play in the post and seat tube. I opened it up today and wow wear on the post and tons of grit inside. What do I do to clean this out and is all that sand traveling down into my BB area? I have not even ridden it in the rain, only damp roads 3x , I do no see how this could be considered acceptable by trek. View attachment 485609
View attachment 485608

I’ve had exactly the same problem, I ended up buying a new seat post and within 6 months of dry or damp riding the exact same problem again. It’s a terrible design. I tried to discuss it with Trek but they weren’t interested in the slightest, they just took my money knowing the same problem would happen again. Won’t be buying Trek again.

 

[PoorInRichfield]

...

 

[PoorInRichfield]

Not a great photo because it's dark in my "pain cave" basement, but this is a 3D printed cap I bought from someone on Facebook to fill the slot in the seat tube. While this 3D printed cap won't solve all the issues of water and dirt getting into the seat tube, I think it looks much better on a $6k bike than electrical tape.

Purchased via Facebook user Peter Henriksen. See this thread: Log into Facebook /groups/514423345385271/posts/2507701539390765/ (Take the space out after ".com". This forum doesn't like Facebook links.)

Note that the seller lives in Denmark, so it takes a while to get the item if you live on the other side of the ocean like I do.

 

[Roadiegraveller]

@PoorInRichfield where did you get this please, would like to get similar?

is the tail plug supposed to do this job, not that I seem to have one supplied?

 

[PoorInRichfield]

@PoorInRichfield where did you get this please, would like to get similar?

Purchased via Facebook user Peter Henriksen. See this thread: Log into Facebook /groups/514423345385271/posts/2507701539390765/ (Take the space out after ".com". This forum doesn't like Facebook links.)

Note that the seller lives in Denmark, so it takes a while to get the item if you live on the other side of the ocean like I do.

 

[PoorInRichfield]

If I had some 3D printer skills, I'd print a seat post grommet to keep out water from the top, similar what used to be on older Madones: