January 3, 2006

    I have an older Celo Europa racing road frame from the late 1970s made from Columbus SL tubing. I am trying to determine the correct seatpost size for this frame. 27.2 is too big and 26.8 is too small.
    I've checked the inside tubing measurement with calipers to see if 27.0 (1.063") would fit, but looks like it might be a little tight, as areas of the tubing measure slightly less than 1.063". I'm having problems finding a chart and want to make sure I’ll buy the correct size seatpost. Can you help?


    In addition to one sweet frame, you have what experts call a “baseball bat” seat tube (obviously, not experts in poetry), in that it tapers. Frame makers do that to add rigidity to frames, and they also added mild frustration when one replaces a seatpost.
    A 27 mm seatpost will probably work unless you need a rather long one—in which case you’ll need a tapered one like the U.S.E. Aero. Alternatively, you could use a 26.8 or even a 25.0 mm seatpost with a shim surrounding the post at the top.
    I think you can learn the needed seatpost diameter for sure only by running that frame over to a bike shop and trying seatposts of several sizes. (Don’t put the 26.8 or 25.0 in without a saddle attached, else you might lose the seatpost. No joke.)
    With frames like yours, getting a seatpost tight seems like such a huge hassle that I think I should say few words about tightening. Ahem. First: You can get into trouble with carbon seatposts if you overtighten them—they’ll simply crack.
    Second: Shims. Those aforementioned experts say you should use plastic shims for carbon seatposts, aluminum for aluminum. Tho I agree about the plastic when using a full-circle shim (think “collar”), I believe you can get away with an aluminum shim on a carbon seatpost if you use just a partial shim (say, 45 to 120 degrees around).
    You can easily make a custom shim from an aluminum beer can. It cuts best wih aluminum snippers, but I’ve done it with regular scissors. I find it helps to drink the beer first.
    Finally: If slippage persists, clean the inside of the seat tube with isopropyl alcohol. Some folks also have luck coating the inside of the seat tube with resin (like Tyre-Grip, whose maker desperately wants to break into the bike industry, tho I don't think they had this application in mind), but that seems extreme to me.

Mr Bike

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