Open Discussion Group

APB Seatpost

Viewing 9 posts - 1 through 9 (of 9 total)
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  • #5485
    Theo
    Participant

    Hello folks,

    I’ve recently acquired a Moulton APB.

    The seatpost that came with the bike seems to have been forced into the seattube, size marking have been scared beyond recognition.

    What is the seatpost size for APB? 34.8mm?

    #5486
    Steven Brandist
    Participant

    Hello Theo

    Yes, I believe you are correct that 34.8mm is the size.
    You can buy an adapter from SJS what will convert down to 27.2mm if you want.
    See here: https://www.sjscycles.co.uk/seat-posts/jtek-seat-post-sleeve-shim-for-moulton-am-older-apb-converts-348-mm-272-mm/

    The seatpost may be the correct size, but corroded in. Water is able to enter the seat tube, but not escape on an APB. This was corrected on TSR frame, it has a small hole at the bottom for water exit/ventilation.

    Steven

    #5494
    Theo
    Participant

    Thanks for the confirmation Steven.

    The seatpost is not stuck inside the seattube, just have lots of scoring from repeated attempts to insert the oversized seatpost into the frame.

    I just hope the seattube is not damaged beyond repair that a proper 34.8mm seatpost would no longer fit.

    #5495

    An automotive ‘O’ ring, obtainable from any obliging car parts store and rolled down the seat-post when adjusted, prevents the ingress of water to most saddle-posts. The topic featured in the last Veteran-Cycle Club ‘The Boneshaker’ magazine; as usual, the V-CC is ahead of the game.

    Bob CC.

    #5496
    Matthew
    Participant

    I’ve literally just picked up an anodised aluminium seatpost for my APB to replace the heavy (and rusty) standard one. This claims, on the box, to be 34.9mm and is a perfect sliding fit. For what it’s worth, it’s a ‘Crank Brothers Cobalt 2’ which several ebay sellers are currently offering for a wide range of prices. I bought mine for a little over a tenner which seemed a bargain to me, especially as it has 400mm of post travel.

    #5504
    Theo
    Participant

    I ordered and received the adapter from SJS.. but adapter itself is too large to fit into the seat tube of my Moulton. I tried inserting a 31.6mm seatost and it seems to fit loosely.

    Was there ever a batch of Moulton APB produced with 31.8mm seattube?

    #5612
    fastbike
    Member

    Was there ever a batch of Moulton APB produced with 31.8mm seattube?

    I have two APBs from the mid/late nineties with 31.8mm seatposts. The seat tube is necked down above the horizontal truss.

    #6042
    Michael
    Participant

    re water ingress into the seat tube on APB, is it a good or bad idea to add a drain hole to allow any water to escape? Just wondering as mine did seem to have a fair amount of accumulated water. I will try the o ring idea but wondering about drilling a hole aswell
    cheers for any thoughts
    Michael

    #6044
    david james
    Participant

    probably not a bad idea, i found mine full up with water!

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