can't find a dropper post that would fit my bike.

Spagoose
Spagoose Posts: 23
edited June 2019 in MTB beginners
Okay so I recently bought my first MTB, an MHT 8.8:

https://www.boardmanbikes.com/gb_en/pro ... t-8.8.html

I'm 5'8" with a 31" inseam, so I wen't for the 18" frame, as the 16" did not have quite enough reach and I also fit nicely in the middle of the recommended height for it.

Now I'm looking for a dropper post and don't think one will fit.

The seattube and cranks add up to about 25", leaving roughly 6" between my arse and the seat tube. In reality I measered 105mm between the top of the seat clamp and the top of the exposed seat tube or 140mm between the top of the seat clamp and the seat rails.

Looking at 100mm dropper posts, you need over 150mm of space to fit one, and even a 75mm dropper post would be a tight fit.

I don't know what I'm doing wrong because every bike I tried before buying, even in the smaller sizes didn't have loads of exposed seat tube like I have seen images of on here. And yes, my leg is fully extended when my heel is on the peddle when it is at the bottom.

This is the only post that I have found that might fit and even then leaves only 10mm of spare room:

https://www.pure-bike.co.uk/images/prod ... 400514.jpg

Am I stuck with having to find a 75mm dropper or am I measuring wrong somehow?

Comments

  • jamski
    jamski Posts: 737
    Why do you need 150mm to fit a 100mm dropper? Sure, you need slightly more, but why 5cm more?
    Daddy, Husband, Designer, Biker, Gamer, Geek
    Bird Aeris 120 | Boardman Team 650b | Boardman Pro FS | Calibre Two.two
  • larkim
    larkim Posts: 2,474
    edited June 2019
    I'm the same height and inside leg as you, just fitted a 125mm reverb dropper to a Voodoo Bizango in an 18inch frame size. I'm struggling to see your issue? The post doesn't need to be fully extended when in use, so if you get a 125mm post and only need 110mm of it to get the right riding position, you just pop up the post to that height, and compress it as low as you can when you need it out of the way.

    Or am I missing something in your analysis?

    (edited, mine is a 125mm dropper, not 100m as originally posted)
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • larkim
    larkim Posts: 2,474
    In otherwords, the collar is flush with the top of the seat post clamp, and the remainder of the post is fully inserted. You don't have to have any of the non-dropping part of the post exposed (providing you can fit the remainder in the tube with the stealth mechanism too - which I can't imagine would be a problem on a Boardman hardtail).
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • larkim
    larkim Posts: 2,474
    https://photos.app.goo.gl/WLWzHAmNTRxU43U7A shows a pic mid-installation - as you can see, collar level with the seat clamp, then the exposed shaft is the fully extended dropper.
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • Spagoose
    Spagoose Posts: 23
    jamski wrote:
    Why do you need 150mm to fit a 100mm dropper? Sure, you need slightly more, but why 5cm more?

    100mm for the moving section of post and 50mm+ for the collar and the rail clamp area. See this diagram where it shows the 100mm rockshock reverb actually needing 170mm to fit the collar and rail clamp in.When in reality I only could fit something that measures 140mm.

    http://ep1.pinkbike.org/p4pb11025848/p4pb11025848.jpg
    larkim wrote:
    I'm the same height and inside leg as you, just fitted a 125mm reverb dropper to a Voodoo Bizango in an 18inch frame size. I'm struggling to see your issue? The post doesn't need to be fully extended when in use, so if you get a 125mm post and only need 110mm of it to get the right riding position, you just pop up the post to that height, and compress it as low as you can when you need it out of the way.

    In reality I could do that way, I was just under the impression that ideally you want your post fully extended when in a riding position etc so you don't have to faff getting it exactly right, just let it all the way out and it's in the right position without having to make minor adjustments on height.

    Also it seems like a waste to me to spend more on a 125mm post when in reality I won't use the whole amount.

    It's just bugging me that people seem to be able to fit 125mm posts with extra space to spare while being the same height, inseam and same frame size while I would struggle to fit a 75mm. I just assume I am doing something wrong somewhere measuring it up.
  • jamski
    jamski Posts: 737
    Spagoose wrote:
    jamski wrote:
    Why do you need 150mm to fit a 100mm dropper? Sure, you need slightly more, but why 5cm more?

    100mm for the moving section of post and 50mm+ for the collar and the rail clamp area. See this diagram where it shows the 100mm rockshock reverb actually needing 170mm to fit the collar and rail clamp in.When in reality I only could fit something that measures 140mm.

    http://ep1.pinkbike.org/p4pb11025848/p4pb11025848.jpg
    larkim wrote:
    I'm the same height and inside leg as you, just fitted a 125mm reverb dropper to a Voodoo Bizango in an 18inch frame size. I'm struggling to see your issue? The post doesn't need to be fully extended when in use, so if you get a 125mm post and only need 110mm of it to get the right riding position, you just pop up the post to that height, and compress it as low as you can when you need it out of the way.

    In reality I could do that way, I was just under the impression that ideally you want your post fully extended when in a riding position etc so you don't have to faff getting it exactly right, just let it all the way out and it's in the right position without having to make minor adjustments on height.

    Also it seems like a waste to me to spend more on a 125mm post when in reality I won't use the whole amount.

    It's just bugging me that people seem to be able to fit 125mm posts with extra space to spare while being the same height, inseam and same frame size while I would struggle to fit a 75mm. I just assume I am doing something wrong somewhere measuring it up.

    I'd want one that extends fully too. Just to make sure it's currently set right, use this to calculate saddle height. On a full suss, I always find saddle height tricky for some reason, and end up having to have it slightly higher.

    https://www.ebicycles.com/bicycle-tools ... ntain-bike

    If you need a 75mm, KS Lev seem to do various ones.
    Daddy, Husband, Designer, Biker, Gamer, Geek
    Bird Aeris 120 | Boardman Team 650b | Boardman Pro FS | Calibre Two.two
  • tallpaul_s
    tallpaul_s Posts: 130
    First, have you definitely set your seat height correctly?

    If so, measure from the top of the seat tube, to the middle of the seat rails, in line with the post.

    Then, look at the One up dropper post. https://int.oneupcomponents.com/collections/dropper-posts/products/dropper-post-v2 You'd be able to get a 110mm drop with 143mm of stack height.

    Oh, and don't get a post that's too long so that you have to adjust it a few mm from fully extended to get the right pedalling position, get one the correct height.

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