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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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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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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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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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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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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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Discussion Starter · #21 ·
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.

Product Automotive tire Automotive design Bumper Tire
 
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