Seatpost prob

[UKBROOKLYN]

Its always something..

All my fancy Italian bits came today for the new build.. But the cheap deda Seatpost is very tight. Before you ask I dropped by my LBS (Shout out to King Kog in Brooklyn) to have a few bits torqued down.. BB Crank etc and they checked the sleeve for me and say its right on.. But the deda stem which says 27.2 on it is way tight... So do I just take off a ton o the very thick paint with ye olde emory cloth or do I roam about and try and find a better made post..

[eddief]

how about some grease?

[staggerwing]

Not trying to be an ass, but what makes you think the "cheap Deda post" is off? Did your shop check it with a micrometer, or a minimum, a caliper. It is much more difficult to check bore diameter accurately. For critical parts, a three point ID micrometer is used, but that is overkill for a bike shop. I typical digital caliper is not a great for measuring ID.

It is also much easier to control OD on a cylindrical post, rather than ID of a sleeve. Although, if the sleeve was properly made, one would think a final pass was made with a reamer.

Even if they had a another post marked 27.2, which slid in easily, doesn't prove the Deda was off.

[oliver1850]

Seatpost actual diameter varies quite a bit. I measured quite a few 27.2s when I was having a similar problem. Largest was a Campagnolo NR, smallest was a Cannondale carbon which now resides in a frame that takes a 27.0 post. I didn't have a Deda so don't know where they fall in the range. I just measured the 3 handiest 27.2s and they all fell in the 27.05 - 27.1 range. Perhaps the Deda is closer to the nominal size. I would measure it and proceed from there.

[David Kirk]

A 27.2 post should be about 27.1 - 27.15 in O.D.

I know it seems odd but the '27.2' is the size of the hole the post fits in not the size of the post itself.

dave

[buldogge]

Post size does vary by .1 or so.

I find Thomsons to be consistently undersized compared to others, for example.

You can also consider having them run a ball hone to the seat tub insert, of course.

-Mark in St. Louis

[UKBROOKLYN]

They have several alloy bars machined to size for checking the bore. Much easier to check a bore with a machined bar than with calipers. Yep the DEDA measures right on 27.2 so theres no space for air and I guess hence the very tight fit.. I guess just taking off a few thou with some emory will do it.

Grease..?? Never Seize always..

[eddief]

this is a framebuilders inside snipe hunt joke, right? :).

A 27.2 post should be about 27.1 - 27.15 in O.D.

I know it seems odd but the '27.2' is the size of the hole the post fits in not the size of the post itself.

dave

[staggerwing]

They have several alloy bars machined to size for checking the bore. Much easier to check a bore with a machined bar than with calipers. Yep the DEDA measures right on 27.2 so theres no space for air and I guess hence the very tight fit.. I guess just taking off a few thou with some emory will do it.

Grease..?? Never Seize always..

If that really is the case, you are going to be a long time making headway with just emery paper. Would be nice if you could chuck it up in a lathe, and go after it with some 220 and 320 wet-or-dry, with some soapy water as a lubricant.

Nice that they have machined stock for go/no go gauges. Really is a proper way to evaluate the situation.

[bobswire]

A Thomson and Ritchie 27.2 fit with no problems if it is the Merlin you're talking about?

[Cat3roadracer]

I have a Thomson Masterpiece 27.2 in my Extralight, fits just fine.

[tttsmm]

strange things these seatposts. i had a new 27.2 PMP which got stuck in my frame when i tried to install it, shop hammered it out and it measured 27.3 in some places. my old deda fit with no problem.

[ultraman6970]

What bike are u talking about to start with??? the shop used a reamer???

THat the frame apparently takes 27.2, doesnt mean the seat tube is 27.2, and if the frame is italian... doesnt mean it either.

The problem could be the clamp that is not rounded, it could be the seat tube that hasnt been reamed ever and in that case probably is not round inside then you have those problems, it could be that the reamed area is too short and if the seat tube is super long then it gets tight as deeper it gets.

Not all the shops have the right tools, not all the shops have mechanics that have seen everything neither troubleshoot stuff specially because they assume wrong things.

1st thing to do is to measure the seatpost right, then ream that seat tube as it should be.

[UKBROOKLYN]

We are talking about the Merlin.. and since we checked the shaft at the shop with the correctly sized bars I am not about to start messing with the frame.

I have spent a little while with the emery and its getting there.. Seems like there can be quite a bit of difference in post size.. The Deda post has that super gloss black look and that probably is the culprit as that kind of paint is very thick.

probably serves me right for being a cheap one to begin with...oops I meant buying a cheap one..

[tuxbailey]

i have a thomson masterpiece 27.2 in my extralight, fits just fine.

+1