measuring seat tube size

Discussion in 'Cycling Equipment' started by bent_sprocket, May 30, 2003.

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  1. bent_sprocket

    bent_sprocket New Member

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    what's the best way to measure my seat tube so that i can get the correct seat post size?

    i know that the LBS has some cone-shaped thing, but my LBS isn't that local and i'd like to order the correct size post for my almost done fixie.
     
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  2. Lee

    Lee Guest

    Ben Tsprocket writes:

    > i know that the LBS has some cone-shaped thing, but my LBS isn't that local and i'd like to order
    > the correct size post for my almost done fixie.

    Cycle over to Radio Shack and borrow one of their electric measuring calipers.

    Or buy one off ebay for about $12, as I did. Like one of these:

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2325019586&category=29525

    Pretty interesting what you can measure once you have one of these gizmos :)

    Lee
     
  3. Do you have any 'machinist' buddies with a micrometer or a caliper?

    Do you or your friends have any seatposts that you can try in the hole?

    Lewis.

    ...................... bent_sprocket <[email protected]> wrote in message
    news:<[email protected]>...
    > what's the best way to measure my seat tube so that i can get the correct seat post size?
    >
    > i know that the LBS has some cone-shaped thing, but my LBS isn't that local and i'd like to order
    > the correct size post for my almost done fixie.
     
  4. On Sat, 31 May 2003 00:30:17 +0950, bent_sprocket wrote:

    > what's the best way to measure my seat tube so that i can get the correct seat post size?
    >
    > i know that the LBS has some cone-shaped thing, but my LBS isn't that local and i'd like to order
    > the correct size post for my almost done fixie.

    I presume you don't have a decent caliper, which would be the best way. But you probably have
    another bike. Try the seatpost from that. You may get lucky, or at least have an idea of what
    the size is.

    --

    David L. Johnson

    __o | What is objectionable, and what is dangerous about extremists is _`\(,_ | not that they are
    extreme, but that they are intolerant. (_)/ (_) | --Robert F. Kennedy
     
  5. On Sat, 31 May 2003 00:30:17 +0950, bent_sprocket wrote:

    > what's the best way to measure my seat tube so that i can get the correct seat post size?
    >
    > i know that the LBS has some cone-shaped thing, but my LBS isn't that local and i'd like to order
    > the correct size post for my almost done fixie.

    If you have the original seat post look at it, some seat posts have the size stamped on them.
    Otherwise you can't beat calipers, got some metric ones at Home Depot for ~$12.
     
  6. A Muzi

    A Muzi Guest

    "bent_sprocket" <[email protected]> wrote in message
    news:[email protected]...
    > what's the best way to measure my seat tube so that i can get the correct seat post size?
    >
    > i know that the LBS has some cone-shaped thing, but my LBS isn't that local and i'd like to order
    > the correct size post for my almost done fixie.

    Seat tube ID are notoriously difficult to measure with a caliper due to out-of-roundness and
    the fact that that oval variance can easily be greater than the difference from one size to the
    next (0.2mm).

    Ideally, you should find the actual specification and clean the bore with a parallel-blade
    adjustable reamer ( referenced by the mysteriously anonymous "ant" here recently).

    Failing that, another effective method is to slip in seatposts until one is found which slides
    neatly with full contact and then confirm that by tryng the next larger size which should start with
    difficulty but be obviously too tight.

    On a beaten-up seat cluster, slipping a slightly smaller post in about 30mm and pressing toward the
    back of the bicycle will usually cure dented/crushed seat binder problems. You end up with little
    contact in the first inch or so until the bolt is tightened, so you don't gouge up the new post with
    the mangled edge near the slit.
    --
    Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
     
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