On Sun, 16 Jan 2005 20:39:07 +1100, "hippy"
> may have said:
>My track bike has a Zeus 26.8mm seatpost fitted
>which appears to use fairly thick alu tube.
>Does anyone know how much of this post I
>should have below the clamp/in the frame?
>The post is 180mm long and currently has
>75mm inside the frame.
In my opinion, for conventional frames, there are two answers to this.
The first one is that there is usually a "minumum insertion" mark on
the post itself; this is the amount that the maker of the *post* feels
must be inside the seat tube in order to provide a safe result.
The second answer is that no matter how far down the post you find the
minimum insertion mark, the post still needs to be deep enough in the
seat tube that the end of it is slightly past the bottom of the joint
with the top tube. I compare the post to the frame; if the post's
min-insertion line is above the clamp when the end of the post is
about 15-25mm below the top tube's lower extent, then I use the
manufacturer's mark. If the min-insertion line is below the clamp at
that point, I make a new mark on the post and use that as *my* minimum
Frames with peculiar designs, and drop-frame bikes, have to be
evaluated differently, of course.
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