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Dropper seat post on new bike too high!

Just taken delivery of a new MTB, which comes with a dropper post. However, even with the post fully slammed into the frame the post still high! Not by much, maybe about 0.5 - 1 cm. The post has 170 mm travel, which is pretty long. Smaller frames sizes come with a 150 which I think would have been better. I'm pretty sure the frame size is correct - I'm well with their stated height range, and I took the bike for a test ride just now, and I think it feels fine, if a bit odd because I'm coming from a 22 year old hardtail. What are my options? Buy another, shorter, post? I don't expect the retailer to be much help. It was Go Outdoors.


  • reaperactualreaperactual Posts: 1,163
    edited February 2022
    You've not got the wrong frame size. Hard to know (as it's based on inside leg measurement) whether a dropper will be correct if you didn't get a test ride or chance to try the bike first.

    Same thing happened to me with a medium frame and a 150mm dropper.

    The answer is to get a replacement with less travel. I sold mine on eBay 'as new' and got decent money for it.
  • bungle73bungle73 Posts: 758
    No chance to try the bike. It's a Polygon, so online only.

    I've come to the same conclusion, and have pulled the trigger on a 150 Brand X dropper from CRC. I think it's actually the same as the one I have (apart from the length), just rebranded.

    I actually took a photo of the bike a few hours ago (to show someone), and when I looked at it just now I think the seat post is just far too long for the frame size.
  • bungle73bungle73 Posts: 758
    Actually the sizing chart went by height for some reason. This is my third bike bought online. I've always gone by the sizing chart given, and it's never been wrong. I did a quick check yesterday, and the handlebars (measured to the point at the stem) are around the same position as my other bikes so I'm guessing that it's correct.
  • bungle73bungle73 Posts: 758
    I just compared it with my old MTB, and it doesn't look massively different size wise. Of course, it's a bit hard to compare because they're two entirely different kinds of frame. I would say it's equivalent though.
  • steve_sordysteve_sordy Posts: 2,420
    This is a tricky one. I bought a YT Capra on-line and checked the geometry, but I only checked angles, reach and stack. When The bike arrived, the saddle was 10mm too high for perfect comfort. I could live with it, just. But then after a few months, my 150mm Reverb dropper failed and I managed to swap it for a 125. :)

    When I was buying my current bike (no test ride), warned by the above experience, I checked the seat tube length and the crank length. I then had to check the dropper dimensions. You need to find out the dimension from the bit that butts against the seat tube to the top of the dropper. Then add on the height of your saddle. It's a bit of a faff and the info is not readily available, you have to search for it. You may be able to get the dropper dimensions you need by asking someone on here. Also, don't forget that websites that sell that dropper often include dimensions, usually on one of the many pictures they make available.

    Then check all that against what you know for sure - your current bike!

    I did all that and the bike I bought was bang on the max height I could accept. I really wanted the bike, so I pressed the button. In practice, I believe that if I could, I would drop the saddle by only a few mm (who knew that your 4r$e could sense height so well?)

    For perfection, all I need to do is to buy some new boots where the sole is not so badly worn down and maybe wear some thicker socks! :D
  • reaperactualreaperactual Posts: 1,163
    edited February 2022
    You've ended up in the same situation which is easy to overlook and assume it's all gonna fit.

    A 170mm dropper does seem a bit big for the average rider looking for an average fit mtb so I guess 'the retailer' could take some of the blame on this. πŸ€”

    Like Steve said from this point stick with the new bike and dropper fitting. The only measurement comparison needed now is the bottom of seatpost collar to the centre of the saddle rail clamp, (stack height).

    The Brand X sold on C.R.C. has the diagram so you can work out stack height from the measurements given (deduct max insertion from overall length) if you haven't checked that already.

    Having said that, your dropper is probably a rebranded Brand X so likely you'll be fine with the 150mm dropper anyway.
  • bungle73bungle73 Posts: 758
    The new post was delivered today and fitted. Just went for a test ride and it now feels more like a bike that is right for me.

    There was a bit of a concern when I first fitted it because, when measured roughly, even with the post slammed, the height seemed already around my prefered height. This was a worry in case this one turned out to be too high as well. However when I sat on it static, and when I went for a ride it felt fine. In fact I think it may be a tad too low, so I might need to raise it a bit.
  • reaperactualreaperactual Posts: 1,163
    edited February 2022
    With all things being equal as in same dropper, saddle, padded shorts, shoes and socks, etc. πŸ˜ƒ that 20mm less travel should equate to a 10mm lower saddle height and a 10mm gap between the collar and seatpost clamp.

    Not big numbers but definately enough to make the difference for proper fit and comfort. πŸ˜ŽπŸ‘
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