I currently have an older Dahon Mariner with a Telescope seat post. The third wheel that functions as the "third leg" (when the bike is folded) has broken off. To compensate, could I switch out the telescope seat post with a longer seat post. When the seat is dropped for folding, my intention is that the length of this seat post will resume the function of this third leg.

Is this possible?

My model does have a hole in the frame's bottom, allowing a long seat post to pass through (and function as a stand).

Update: Thank you for all the comments below. I am still looking to do this and now have the measurements of the current Telescope seat post. They are 34.2mm and 28.x respectively. The bike does have a small plastic shim between the frame and the bottom telescope seat post pole.

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Update: It was able to do it.

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  • 1
    "Is it possible?". Well, I would say it is possible if it's not impossible. And most probably is a perfectly fine solution with no side-effects. Nov 21, 2012 at 13:58
  • Do different seat post have different diameters? The telescope seat post on the folder is wider than the seat post on my full size, off the shelf bike.
    – Rick
    Nov 21, 2012 at 15:54
  • 1
    Modern Dahons rest on the bottom of the seatpost, and have no third wheel. Without knowing the details of your model, I doubt anyone will know whether a suitable replacement seatpost exists though. Does your frame seattube allow a seatpost to go right through and out the bottom, like modern Dahons?
    – armb
    Nov 27, 2012 at 16:24
  • 3
    Current Dahon seatposts are 33.9mm diameter. The standard ones are 580mm long but there are longer ones available (e.g. thorusa.com/accessories/seatpost.htm), and suspension posts, and Biologic ones with an integrated pump. But I can't tell you whether your older Dahon used the same size - I've never seen one with a "third wheel".
    – armb
    Feb 5, 2013 at 14:19
  • 2
    Here's a replacement/aftermarket "third wheel". I don't know whether it will fit your older size seatpost though handsonbike.blogspot.sg/2012/07/…
    – armb
    Oct 1, 2013 at 10:14

1 Answer 1



Of course it's possible, you just need to find a telescopic seat post on the market that is longer than the one you have.

Your measurement of your post might be a bit off though, I'm guessing that from your 28.x measurement, and the fact that I don't think 34.2mm is a seatpost size... not one that I'm familiar with anyways. In which case chances are your post is a 34.9mm, not a 34.2mm, and that something like this will do the trick:


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