In a message dated 11/4/03 11:26:53 AM Pacific Standard Time,
goodrichbikes@netzero.net writes:
> Tubing makers have manufacturing tolerances. When you put a caliper on a
> pile of seat tubes, those tolerances are quite evident. Factor in heat
> distortion which is especially evident in brass brazed lugs and this
> explains the different sizes of seat posts.
>
> I think it was JBZ's Tesch that had a slipping seat post. Tesch was/is a
> great builder but there's a good chance that the seat lug was brass brazed.
> There's nothing wrong with that but at brass brazing temps the seat tube
> will distort. The better the brazer the less it will but regardless it will
> distort some. When solid binder ears collapse against each other generally
> this points to the seat tube ID isn't round and/or the seat post isn't sized
> correctly to the frame. I think JBZ's fix is a good one but I'd measure
> that seat tube ID. If it isn't round or at least close, slipping might
> start up again.
>
Good point! It also reminds me that even though Campagnolo seat posts are
fairly consistent in being close to size, they can be undersize. It's interesting
to have a digital caliper and actually measure them. Some of the less
expensive posts out there are WAY undersize. I have a Columbus post that is missing
all the clamping hardware that I'm hanging on to because it is EXACTLY 27.00mm.
It makes a nice fit gauge.
Stevan Thomas
Alameda, CA