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Teach me about dropper posts

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Teach me about dropper posts

Old 04-25-20, 02:08 PM
  #1  
unterhausen
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Teach me about dropper posts

If I want to internally route a dropper cable, does it just take a port on the seat tube? And a few zip tie cable holders on the down tube? If anyone can link to pictures of a frame with this, it would be great. I decided my new gravel bike needs a dropper post
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Old 04-25-20, 02:27 PM
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wsteve464
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Great minds, I am thinking of doing this on my next one. Only thing stopping me is the Di2 battery and relocating it out of the seatpost, maybe the steerer tube.

I will put a port at the top of the downtube either on the same side as the rear brake hose or the other side not sure yet. The cable will run internally down the down tube through the bottom bracket and up the seat tube. There is enough room to run the cable above the bottom bracket bearing assy with a little grinding on the seatube down tube junction if you are using a BSA BB shell, PF30 EVO86 have enough room.

You could run it externally to the bottom of the seat tube and internally from the bottom of the seat tube. There are plenty of different cable mounts you could braze on along the downtube to hold the cable in place.



They also make dropper posts that run the cable externally all the way to the top of the seat post, not a very clean look.
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Old 04-25-20, 02:57 PM
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unterhausen
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The ones I remember seeing on mountain bikes have a port at the front of the seat post at the bottom. Are you going to run the casing in the bb? seems like the radius might be a bit tight. Do you have your post yet?
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Old 04-25-20, 03:25 PM
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wsteve464
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My FS mtb has the dropper cable hole external to the bottom front of the seat post then internal.

Yes I will run the casing inside the tubes. I have run the front derailleur cable this way and no problems with the radius. Take a piece of housing and cable and mock up the bend and check for ease of movement, grinding away some of the ST/DT junction inside the BB helps. The nice thing I have found about making the frames myself for me only is that I can try different ideas and not have to worry about how well the idea works. I can always redo it or move on to another build.

Another option spend $800 on a Rockshok wireless dropper. LOL.

Check with forum member Dr Isotope he has one on his bike.
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Old 04-26-20, 05:22 AM
  #5  
dsaul
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Short curved section of stainless tube(around 1.5 to 2"long) silver brazed into the seat tube to direct the dropper cable housing and try to keep it centered in the seat tube.


The same frame after powder coating.
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Old 04-26-20, 08:06 AM
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unterhausen
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Thanks David. Is that a vari-wall seat tube?
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Old 04-26-20, 12:12 PM
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dsaul
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Originally Posted by unterhausen View Post
Thanks David. Is that a vari-wall seat tube?
Yes. This frame does have the Vari-Wall curved seat tube. All of my other curved seat tube frames were Nova bent down tubes with a collar welded on top.
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Old 04-27-20, 05:09 PM
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Like Dsaul, I just use some 1/4x.028" tubing, file an oblong hole to get the entry angle the way I want and braze it in. My preference is to put the entry in the DT near the HT on the drive side. I mill out a 1/2" slot in the ST where it's hidden by the DT, and a 1/2" slot in the BB to cover venting for both tubes and to accommodate the cable housing. It makes installation harder than running externally then entering the ST, but I like the clean look.
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