# 2020 Domane Seat Mast... Begging for Water in Frame?



## PoorInRichfield (Nov 30, 2013)

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.


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## velodog (Sep 26, 2007)

Fenders.


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## PoorInRichfield (Nov 30, 2013)

velodog said:


> Fenders.


 Yeah, I guess that's one option!


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## 202cycle (Sep 13, 2011)

There is a little plug that should be on the end of the seatpost. It's called the seatpost "tail". Part #W581152. That little piece is designed to keep water out of the frame. It should have been installed by the shop, or provided to you when you got the bike.


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## PoorInRichfield (Nov 30, 2013)

Yup, the rubber plug is installed in the base of the seat post mast. Seems like an odd solution to the problem, however. I'd rather keep dirt and water out of the frame and seat tube entirely rather than have it collect in the seat post


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## ToiletSiphon (Jul 23, 2014)

If it was my bike, I'd simply put a piece of electrical tape over that. Not the most elegant but gets the job done.


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## velodog (Sep 26, 2007)

How about applying some sort of release agent and then filling the slot with silicone or sumsuch forming a removable plug? It may work but as long the release agent works there is no damage if it doesn't work.
Just test that the release agent works with what ever you use to form the plug before attempting on the bike. If it works some sort of "tail" could be embedded into the silicone, making removal easy.


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## cxwrench (Nov 9, 2004)

PoorInRichfield said:


> Yup, the rubber plug is installed in the base of the seat post mast. Seems like an odd solution to the problem, however. I'd rather keep dirt and water out of the frame and seat tube entirely rather than have it collect in the seat post


You're overthinking it.


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## MagicHat77 (May 11, 2021)

Ok I had the same problem. Took some photos of the part mentioned and how it installs. I do recommend addressing this if you find it on your Domane also - inside my seat mast was gritty after only 35 miles. I've also added a piece of electrical tape over the slot as extra coverage.

1. Pic with the insert missing








2. seatpost "tail". Part #W581152.








3. Here is installed in bottom of seat post.








4. Installed back into seat mast - gap where I could see wires before is now closed.


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## PoorInRichfield (Nov 30, 2013)

@MagicHat77 What model Domane do you have? Is it an SLR? Yours looks quite different than my 2020 SL7 in that there are no bolts nor junction box cover below the seat mast bolt on my bike. I also don't have any electronics in the seat mast... Is that your Di2 battery cable? Mine battery is mounted in the downtube.

While I still love my Domane after owning it for over a year, I haven't changed my mind about this mast design as being something that could/should be improved on future Domanes. It does let dirt into the frame and I now have chipped paint on the frame from sticking and twisting the Allen wrench into the odd slot on the frame as I frequently have to remove the seat so the bike fits in my vehicle.


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## MagicHat77 (May 11, 2021)

PoorInRichfield said:


> @MagicHat77 What model Domane do you have? Is it an SLR? Yours looks quite different than my 2020 SL7 in that there are no bolts nor junction box cover below the seat mast bolt on my bike. I also don't have any electronics in the seat mast... Is that your Di2 battery cable? Mine battery is mounted in the downtube.
> 
> While I still love my Domane after owning it for over a year, I haven't changed my mind about this mast design as being something that could/should be improved on future Domanes. It does let dirt into the frame and I now have chipped paint on the frame from sticking and twisting the Allen wrench into the odd slot on the frame as I frequently have to remove the seat so the bike fits in my vehicle.



Sorry I didn't clarify.

The pics are from a Domane+ HP 2021 model. The wires are for the rear light on the seat. I don't like the design either and feel best with a piece of tape over it.


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## PoorInRichfield (Nov 30, 2013)

< OP
I went to remove my seat post this evening to get my bike in the car for a trip. I haven't removed the seat post since last year at this time. To my surprise, the binder bolt was insanely hard to loosen and I know for sure I didn't tighten it that much as I don't want to damage the carbon. Because I've been caught in rain and wet gravel this summer, the bolt area appeared a bit gunky and corroded. I've already chipped the paint on the slot in the frame because the Allen wrench occasionally slips despite being careful.

I did get the binder bolt loose by using a longer Allen wrench and squirted some Teflon lube on the binder bolt to loosen it up. So note to myself and other Domane owners... It might be worth removing your seat post, cleaning it up, and lubing the binder bolt a little each year (or more) before your seat post becomes a permanent fixture in the frame.

Seat post design aside, I love, love, love my Domane after owning it for nearly 2 years now.


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## Andyk32 (Feb 18, 2021)

Question for the group, does anyone's seatmast clunk or rock back and forth, even when properly torqued? I have a P1 Domane SLR 7 and the darn seatpost clunks. I can grab the seat and twist it side to side, and visibly see it clunk in the mast. Any suggestions? Thanks!


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## JSR (Feb 27, 2006)

Andyk32 said:


> Question for the group, does anyone's seatmast clunk or rock back and forth, even when properly torqued? I have a P1 Domane SLR 7 and the darn seatpost clunks. I can grab the seat and twist it side to side, and visibly see it clunk in the mast. Any suggestions? Thanks!


Is it actually the mast that’s moving or the rail binding mechanism? The rail binder is a funky clam shell design that has a number of ways to screw it up. I’d start there.


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## siggs (Feb 4, 2011)

Andyk32 said:


> Question for the group, does anyone's seatmast clunk or rock back and forth, even when properly torqued? I have a P1 Domane SLR 7 and the darn seatpost clunks. I can grab the seat and twist it side to side, and visibly see it clunk in the mast. Any suggestions? Thanks!


I have a domane Sl5 and I had some problems. The adjustment bolt on the seatpost seized so tight it was impossible to undo it then stripped. They have to extract it with a easy out. I got the bike back and 4hrs later it's clunky like you say. There's massive play at 7nm it's right frightening. The play is side to side. I wrote support to see what to do. There does not seem to be excessive wear, I hope this isn't like a canyon thing.


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## siggs (Feb 4, 2011)

Please take a look at the video and let me know if anyone else has this problem or seen it? I've tried to lower the post and it does the same thing. It's torqued to spec or just over.
New video by denny mires

New video by denny mires


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## PoorInRichfield (Nov 30, 2013)

OP here... Two years into owning my Domane and while I still absolutely love the bike, this seat mast issue is still an issue. I just pulled the seat mast out while my bike is on the trainer for the Winter and tons of dust and debris came out, not to mention the seat post is so scratched-up that I hope I never have a need to raise the post as it'll look awful. 

Some people on Facebook are posting pics of using an old innertube to cover the top of the seat mast as the big adjustment slot. I think this is a great idea. Now I just have to figure-out what size tube works best as the 700x28c tube I just cut-up to try this was way too small 😖

This isn't my bike, but this is what people are doing (short of using fenders to keep dirt out of their frames)...


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## siggs (Feb 4, 2011)

Hello, I am the one with the other problem of wear inside. The wear was from rubbing inside, the binder bolt on the carbon/paint. The residue must of jammed it up and caused it to wear so it will not hold the post tight at the recommended spec. To answer your question I would probably caulk it with a thing clean bead of black latex caulk, it would look way better. Do you have any movement in the post side to side or back and forth like I show in my video? They ended up replacing my frameset, I would make sure everyone checks their posts for wear and moves it once in a while. Left alone it will probably just sit there seized but if you ever go to sell it or adjust you maybe in for a nasty surprise.


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## PoorInRichfield (Nov 30, 2013)

siggs said:


> I have a domane Sl5 and I had some problems. The adjustment bolt on the seatpost seized so tight it was impossible to undo it then stripped. They have to extract it with a easy out.


I had a similar issue where the seat post bolt was extremely difficult to loosen and ended-up chipping the paint on the "slot" while trying to get the bolt loose. I used some anti-seize I have for automotive purposes and that eventually worked. I question what Trek design engineers were thinking with this design. Did they think we'd all be running fenders? I don't ride my bike in the rain on-purpose but got caught in two rainstorms last Summer and my bike got filthy. Now I know that I have to take the seat post apart and clean everything or else I risk having it seize-up from spray and dirt off the rear tire.


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## PBL450 (Apr 12, 2014)

It’s a design flaw. Yes, there are some ways to minimize the impact, but it’s still a design flaw. I glad you made this thread so people who might be interested in this frame can see that is fundamentally flawed. I got tipped off about a similar design flaw in a seat clamp on a BMC frame. It was 2 years ago and I don’t remember which frame it was, but it helped me understand why the price of the frame was so attractive for a normally very pricey bling. It’s a shame you got tagged with this...


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## PoorInRichfield (Nov 30, 2013)

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:

Seal around top of seat tube that has a "fat section" that will fill the gap caused by the channel in the seat mast.
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.


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## norcallincoln (Jul 3, 2011)

PoorInRichfield said:


> 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 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?


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## Toni_Maloni (4 mo ago)

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!


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## Toni_Maloni (4 mo ago)

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...


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## Peter P. (Dec 30, 2006)

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.


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## Toni_Maloni (4 mo ago)

Peter P. said:


> 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.
> ...


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.


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## velodog (Sep 26, 2007)

Toni_Maloni said:


> 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.
> ...


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


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## Peter P. (Dec 30, 2006)

velodog said:


> 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.


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## siggs (Feb 4, 2011)

Toni_Maloni said:


> 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.
> ...



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.


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