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Discussion Starter · #1 ·
Hey guys,

Today I was adjusting my saddle height and went to lower the post some and could not get it to go down any further.
It is a Crank Bros Highline 31.6 X 125mm. I ended up pulling the whole post out of the seat tube and it appears due to the bend in the tube the bottom of the post where the cable connects is hitting it.
I had the seat post set just below the number 10 mark. I didn't want to force it down any farther.
Just wondering if anyone else has had any issues like this or maybe it's just the way the dropper is made and I may need to get another brand....
I also noticed that right on the outside of where the tube bends behind the shock the paint is chipped off. I need to pull the shock off and inspect to make sure that's all it is.

Thanks!
 

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IDK about your specific situation, but part of getting a dropper is ensuring that at full extension you have enough insertion depth to put the saddle at your normal ride height. Different posts will have different overall lengths, as well as rail to stanchion collar length. Both need to be short enough to ensure the saddle winds up at the correct height at full extension.
 

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IDK about your specific situation, but part of getting a dropper is ensuring that at full extension you have enough insertion depth to put the saddle at your normal ride height. Different posts will have different overall lengths, as well as rail to stanchion collar length. Both need to be short enough to ensure the saddle winds up at the correct height at full extension.
This...OneUp components supposedly has the least required insertion depth. I am running a Fox Transfer on my bike and is less than the stock Bontrager post as well...
 

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Discussion Starter · #4 ·
Thanks guys!

After doing more research I guess at the time I did my frame build I was unaware of the frame max insertion length.... It was my first build & first full suspension!
The Highline has a max insertion of 282mm. I was looking at the Fox Transfer which is 220.5mm for the 125mm length. I guess I will have to go that route now.
I looked at Trek's website, but could not locate a frame max insertion length at all. Doing a rough measurement it appears to be around 230mm or so. I may give customer service a call and see if they can answer that!
 

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To figure out how much insertion depth a frame has, look down the seat tube to see what there, then push a normal seat post down until it stops. Mark the post at the top of the clamp, pull it out, measure from the bottom to the mark. Next measure from the top of the post clamp to the saddle rails when the post is set at your correct pedaling height. Add those two numbers and that's the max overall length for the dropper. Then, the distance at max extension from the rail clamp to the bottom of the stanchion collar of the post you select needs to be less than your measured post clamp to rails dimension.
 

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Bike Yoke has the shortest insertion depth that I found. Also the cable actuator at the bottom of the post can be rotated for additional clearance. I ran into these same issue when I did my build earlier this year.
 

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I had the same issue on my carbon 17.5 Slash. The 125mm stock dropper was hitting the pivot bolt housing and I couldn't get it to the proper seat height. I remedied this issue by throwing the Bontrager Dropper in the trash(figuratively). I then bought a BikeYoke Revive which was an inch shorter in overall length in 125mm. The bottom actuator can be rotated for even more clearance. It's also the best dropper post in in the market. By far.
 

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Discussion Starter · #8 ·
I talked to Trek tech support today and they told me the frame max insertion length for a dropper post on the 18.5" frame is 245mm.
After doing some more measurements I have a total of about 53mm of seat post from the top of the seat post clamp to the bottom of the post collar. According to Crank Bros specs the maximum insertion length including the actuator is 282mm. So that tells me there is roughly 230mm in the seat tube where it bottoms out....
I think I'm just going to switch to the Fox Transfer Factory post with 125mm of travel as it is a few inches shorter for maximum insertion length...
 

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Discussion Starter · #10 ·
trek pivot bolt housing can be filed. use a half round file, and enough material can be removed to get dropper post an inch lower.

Maybe not all Fuel EX's but I know it has been done on at least one.
Yeah I don't want to be filing any bolts down.... I ended up buying a Fox Transfer Factory 125mm from Pro Bike Supply for $293. They are having a sale on all Fox Shox! I should have plenty of room left in the seat tube with this dropper compared to the Crank Bros....
 
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