Re: [CR] Minimum Seatpost Insertion

(Example: Framebuilding)

From: <gpvb1@comcast.net>
To: classicrendezvous@bikelist.org
Subject: Re: [CR] Minimum Seatpost Insertion
Date: Fri, 17 Jun 2005 14:54:12 +0000


I measured some limit lines, both Campy and others, and they tend to be at about 55 mm of post.... Greg Parker Dexter, Michigan

Date: Fri, 17 Jun 2005 00:02:31 -0700 From: Kurt Sperry <haxixe@gmail.com> Cc: classicrendezvous@bikelist.org Subject: Re: [CR]Minimum Seatpost Insertion

As a weight weenie sort, on my off-topic bikes I've sometimes trimmed the posts to slightly less than 80mm insertion length and never had any problems. I'd read somewhere years ago that 2 1/2" is just sufficient. Not that that means a lot of course. I'd think the post itself would be fine if it's reasonably thick walled, but I might be concerned about the seat tube in this instance. It's definitely not as safety critical as a stem in any event. Anyone other weight weenies who've trimmed posts?

Kurt Sperry Bellingham WA


> I recently bought the Haral frame on eBay made of Excel CSK tubing which
  
> has a carbon sleeve inside a thin-walled steel tube. This presents a problem
> with what sort of seatpost to use. The carbon sleeve starts approximately
> 80 mm below the top of the seatlug. A 26.8 post will go in only that far, so
> the inner diameter of the carbon layer is smaller, perhaps 26.2.
> The seller says the post which came with the frame, which he hasn't found
> yet, was an American Classic 27.4 mm cut short to fit into the seattube
> section above the carbon sleeve. But it isn't clear whether this was
> original. Also not clear what post the frame manufacturer recommended. I
> could buy a 27.4 Kalloy Laprade and cut it to fit, but is 80 mm of
> seatpost insertion adequate? The frame is 55.5 to 56 cm ctc which is at
> the tall end of my range, so I'll probably have only about 50 mm of post
> exposed above the seatlug (not counting the post head). Does 80 mm insertion
> with 50 mm exposed sound safe? Does the thin wall of the steel tube increase
> the risk of the small insertion? Someone recently mentioned a very short
> Campy Record post from the early 70's. How long was that post and what
> would its typical insertion length have been?
> I suppose I could use a post which fits inside the carbon sleeve and shim
> the section at the top of the seattube. Will any standard shim work for a
> 27.4/26.2 diameter?
>
> Regards,
>
> Jerry Moos