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Discussion Starter · #1 ·
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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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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Discussion Starter · #5 ·
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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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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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
479461

2. seatpost "tail". Part #W581152.
479462

3. Here is installed in bottom of seat post.
479463

4. Installed back into seat mast - gap where I could see wires before is now closed.
479464
 

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Discussion Starter · #10 ·
@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 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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Discussion Starter · #12 ·
< 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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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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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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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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Discussion Starter · #17 ·
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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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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Discussion Starter · #19 ·
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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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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