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  1. #1
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    Al frame - drill internal dropper hole

    hi,

    i have a Sturgis NX fatbike that has no internal dropper routing. now i have the choice of buying a 125mm external dropper (on sale now from CRC for $107) or a 150 mm internal (same price). My seatpost sticks out about clsoe to 300 mm, so I'm a bit concerned 125 mm isn't so worthwhile.
    I don't care about the looks, more about the limited height with external routing.
    My riding is mellow, no real jumps etc. I'm 180#. I more want it to go downhill (I'm really slow,and being all the way up doesn't really help). My wheels really never leave the ground.

    Is it OK to drill a hole in seatpost and what are best locations? I read not near welds. I have a frame bag in the triangle. ideally the hole would be on the side. but i read in the middle is better. I could live with the conflict of cable-frame bag, but not ideal.

    I realize this voids any warranty (not sure I have any, bike is more than 1 year old). But I never heard of a bike breaking at the seat tube.

    I know the safe choice is external, but I want to make the drop worthwhile and 125 mm looks very little. any future bikes would have internal, so i could re-use the post as long as it has 30.9 mm.

    I know there are hundreds of threads and opinions already, but what is a reasonably safe procedure?
    2018 Motobecane Sturgis NX
    2016 Giant Toughroad SLR1

  2. #2
    EAT MORE GRIME
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    No it is not ok to drill a hole


    having said that

    the best location would be a few inches above the bottom bracket, opposite the location a front derailleur would go if you had one


    see in this pic, this is a Trek Farley and you can see the plastic nubbin covering up the internal dropper cable hole in the same area I mentioned..however this is stronger than a plain hole (which is why it's not recommended to do to just any bike) but this is the best location

    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  3. #3
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    Quote Originally Posted by 127.0.0.1 View Post
    No it is not ok to drill a hole


    having said that

    the best location would be a few inches above the bottom bracket, opposite the location a front derailleur would go if you had one


    see in this pic, this is a Trek Farley and you can see the plastic nubbin covering up the internal dropper cable hole in the same area I mentioned..however this is stronger than a plain hole (which is why it's not recommended to do to just any bike) but this is the best location

    thanks for the response. My seat tube has the water bottle bosses. So they already have 2 holes if you will. Couldn't I just drill one of those out and enlarge? It wouldn't need to be much larger than it already is. I assume the frame either has some reinforcement there or doe not need it.
    2018 Motobecane Sturgis NX
    2016 Giant Toughroad SLR1

  4. #4
    EAT MORE GRIME
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    I suppose you could repurpose the bottle mount but the hole needs to be elongated slightly so cable goes in at an angle /
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  5. #5
    Out spokin'
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    Quote Originally Posted by HerrKaLeun View Post
    thanks for the response. My seat tube has the water bottle bosses. So they already have 2 holes if you will. Couldn't I just drill one of those out and enlarge? It wouldn't need to be much larger than it already is. I assume the frame either has some reinforcement there or doe not need it.
    You are playing with fire on an aluminum frame. Aluminum's fatigue life is zero, that's why any ports into the frame are reinforced. On many aluminum frames, water bottle bosses are riv-nutted in, this strengthens the initial hole. If you drill out the riv-nut, you defeat it's added strength. The tube may develop a tear there beginning at the stress riser (aka the hole).

    I'm not saying it definitely won't work, but it's extremely risky.
    =sParty
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  6. #6
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    Quote Originally Posted by 127.0.0.1 View Post
    I suppose you could repurpose the bottle mount but the hole needs to be elongated slightly so cable goes in at an angle /
    Thanks. I just saw the "on sale" 150 mm internal dropper is sold out in 30.9 mm. And the other ones are more expensive than an external I meanwhile found. So I'll just go external. Less risky anyway.
    2018 Motobecane Sturgis NX
    2016 Giant Toughroad SLR1

  7. #7
    used to be RipRoar
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    If you ever did do that it is important to chamfer the edges of the hole inside and out so no sharp square edges exist. Helps prevent cracking.

    I've done this for an internal dropper no issues over few years of hard riding. I would say seat tube - frame design plays a big part in deciding if its a go or not.

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