Aluminum seat tube reaming depth-
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  1. #1
    mtbr member
    Join Date
    Feb 2007

    Aluminum seat tube reaming depth

    Could use the input of framebuilders/engineers here if I may be so bold?

    I've just restored an '87 Cannondale SM400, part of which involved purchasing a NOS 27.2mm post to replace the (incorrect) 27.0mm one fitted when I bought it.

    However, I discovered that the seat tube has only been reamed to a depth of about 7.5". Looking down the seat tube I can see the lip at the edge of the factory reaming, and there's about another 3" or so until the upper bottle boss.

    Having tried a 26.8mm post in, which inserted fully to the bottle boss, I assume there'd be no issue in extending the reamed depth down further? It's only 0.2mm wall thickness to come out (tube OD is 32.0mm), which has obviously already been done on the top section. I've emailed Cannondale themselves but I doubt there's anyone working there now who would have been there in '87!

    TIA for any input

  2. #2
    mtbr member
    Join Date
    Dec 2012
    Seems to me it would be far easier to trim the length of the seatpost.

  3. #3
    mtbr member
    Join Date
    Feb 2007
    It technically would, but given that it's a NOS post I'd rather not. Plus, increasing the depth of the factory ream widens the usable height range with an uncut post.

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