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Old 01-14-22, 01:05 PM
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Originally Posted by tiger1964 View Post
Now that's a bunch of detail I can sink my teeth into! Thanks. BTW, maybe there's very little on earth that's 100% round; I just tried the outside of the seat tube at several points and various "rotations" and as I turn the micrometer, the readings change a wee bit. Anyway, it seems to be 28.2mm but that is including the thickness of the new powder coating. The micrometer is digital and has a "zero correct" feature.

No "pinch/taper" to the seat tube slot at all.

Checking again, inside of seat tube does average about 27.2, and the diameter of the seat post is 27.2; hmm, is this the problem due to "nominal clearance between a seat post and seat tube is typically 0.2mm diametral "? Again, the years dim the memories and I was 18 years old, working in a bike shop and assembling this bike from a bare frame and mostly grabbing stuff from the parts bins, so I may have succumbed to "get a bigger mallet" so I may just be looking at a post never intended to fit.
OK, it appears that it is built with metric standard tubing like other Zeus of the era. The nominal outside diameter is almost certainly 28.0mm. With an inner diameter of 27.2mm, that would mean the wall thickness is only 0.4mm! That's very thin. Reynolds didn't have anything in that range until they introduced 753. It appears that someone used a reamer or similar tool at some time, to enlarge the inner diameter, possibly to accept a certain seat post. I've seen cases of overly aggressive factory reaming, but not to this extent.
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