K2 / Proflex Riders Group

General => Tech Forum => Topic started by: crogthomas on May 02, 2007, 06:31:18 am

Title: 656 Seatpost size?
Post by: crogthomas on May 02, 2007, 06:31:18 am

Does anyone know what size seatpost a 656 is supposed to take?
I’m sure this question has been asked hundreds of time before, but I couldn’t find anything with the search.
The post that came with it is steel and I guessed the original one. Its been cut short so I need a new one. It measures 26.8mm, but I’ve just dropped a spare 27.0mm post in there without any problem which makes me wonder if the steel post is actually original....?

I’ve checked here:
http://www.airfreetires.com/Specs/default.asp
which says 27.2mm....
and the Sheldon Brown seatpost database (there seems to be two, anyone else notice this?) doesn’t have the 656.

Anyone know for sure?

Title: Re: 656 Seatpost size?
Post by: orange on May 02, 2007, 08:54:18 am

My guess would be 27.2 - got any lying around you can try - it's a pretty standard size - any mates with a 27.2 seatpost you can try?

Title: Re: 656 Seatpost size?
Post by: crogthomas on May 02, 2007, 11:14:37 am

Yep, picking one up tomorrow to try. I'd prefer to be a bit more scientific than to just keep trying them until I find the right size though.
I suppose its unlikely to be bigger than 27.2, so if that fits I'll stick with it.

Title: Re: 656 Seatpost size?
Post by: orange on May 02, 2007, 07:02:52 pm

to be really scientific you need some Vernier calipers to measure it! ;-)

(http://level1.physics.dur.ac.uk/skills/images/vernier4.jpg)

Title: Re: 656 Seatpost size?
Post by: crogthomas on May 02, 2007, 07:47:05 pm

That is of course the ideal method. The only trouble is that due to the slot in the seat tube the diameter of the hole is somewhat varible, especially since its been squashed down to a different size around an incorrect seatpost for years. What I really need is a miniture bore gauge so that I can measure the internal diameter below the slot.
(http://www.toolweb.com/pics/FOW72-646-400.gif)

Very scientific.
Or I'll just try a 27.2.

Title: Re: 656 Seatpost size?
Post by: crogthomas on May 07, 2007, 08:18:06 pm

For the benefit of future searches, I've tried a 27.2mm post now and it seems to be a perfect fit.
Job's a good-un.

Title: Re: 656 Seatpost size?
Post by: shovelon on May 08, 2007, 07:40:11 am

Good Show.

Just for future ref. Easton CT-2 carbon seatposts won't keep from slipping in my bikes. The only way is to cut the seatpost so that it bottoms at the weld stop. And it just won't work at all in my Oz, and I don't want to destroy the alum insert by over clamping.

Happy riding!
Terry