seatpost issue

[sokyroadie]

I recently bought a Sarto carbon frame which has a non-sloping TT which means I don't have a lot of seatpost exposed. After tightening to 6 NM I noticed the SP was still too loose so I checked it:

At min. insertion and 4" up - 31.6
At middle - 30.9
3.5" from top where I need to clamp - 30.0

The seatpost is a FSA K-Force
I have used it before on a sloping TT frame and it was fine as the numbers indicate.

Anybody got one they can check, I hate to buy another one and have the same issue.

I know FSA:no:, but I like their bars, stems & seatposts - until now.

BTW the seat tube with the seat post collar loose measures 31.4.
Thanks,
Jeff

[lhuerta]

Did u use a LIBERAL amount of carbon paste??

[sokyroadie]

Did u use a LIBERAL amount of carbon paste??

I did, the post is just undersize.

Jeff

[93legendti]

The FSA posts I have used have been very tight. Hard to insert and harder to take out. I wonder if the post is inserted past its max insertion mark?

[AngryScientist]

dont risk screwing around with a carbon frame, trying to overtighten the seatpost clamp to account for an undersized post. get a new post, and dump FSA as an option. the fizik line of cyrano posts are very nice and reasonably priced. i'd get one of those.

[David Kirk]

Unfortunately this is not uncommon with some brands of carbon posts. You're going to need a new post to do it right. I suspect they didn't control the OD that far up the post - some makers do and others don't.

dave

[pdmtong]

Unfortunately this is not uncommon with some brands of carbon posts. You're going to need a new post to do it right. I suspect they didn't control the OD that far up the post - some makers do and others don't. dave

As dave and angry said get a new post. I experienced the opposite - was using a s-works post as a dummy for the shop to clamp while working on my moots and while i got it in, I could barely get it out. meanwhile the moots post slid in and out perfectly.

[sokyroadie]

Fizik Cyrano Alloy post is incoming.

Hopefully Alloy should be more consistent.

Thanks,

Jeff

[David Kirk]

Fizik Cyrano Alloy post is incoming.

Hopefully Alloy should be more consistent.

Thanks,

Jeff

That is a top shelf post - it will fit as it should.

dave

[Peter P.]

This brings up an interesting issue.

It must be the industry's dirty little secret that it's difficult to maintain diameter tolerances on carbon fiber seatposts, leading to all sorts of insertion problems.

Alloy posts on the other hand, can readily be machined to the correct diameter within specified tolerances. I guess you can't machine a carbon seatpost down to the correct diameter.

I wonder if similar problems exist with proprietary carbon aero seatposts such as OEM designs.

[oldpotatoe]

This brings up an interesting issue.

It must be the industry's dirty little secret that it's difficult to maintain diameter tolerances on carbon fiber seatposts, leading to all sorts of insertion problems.

Alloy posts on the other hand, can readily be machined to the correct diameter within specified tolerances. I guess you can't machine a carbon seatpost down to the correct diameter.

I wonder if similar problems exist with proprietary carbon aero seatposts such as OEM designs.

Carbon BB tolerances, rear triangle alignment, seatpost tolerances(mentioned),
HS bearing seats, fork crown race seats, drop out alignment..all sorts of things where on a metal bike/part, it can be machined, or coldset(bent), this stuff cannot be massaged.

[93legendti]

Campy ti post was the worst for insertion...so tight.

[FlashUNC]

Fizik Cyrano Alloy post is incoming.

Hopefully Alloy should be more consistent.

Thanks,

Jeff

I've got one and they are outstanding. Also have a consistent diameter from the bottom all the way to the post head. This should scratch your itch.

[Lewis Moon]

I've got one and they are outstanding. Also have a consistent diameter from the bottom all the way to the post head. This should scratch your itch.

All I got is ditto. The Cyrano is my new favorite.

[RedRider]

This brings up an interesting issue.

It must be the industry's dirty little secret that it's difficult to maintain diameter tolerances on carbon fiber seatposts, leading to all sorts of insertion problems.

Alloy posts on the other hand, can readily be machined to the correct diameter within specified tolerances. I guess you can't machine a carbon seatpost down to the correct diameter.

I wonder if similar problems exist with proprietary carbon aero seatposts such as OEM designs.

You get what you pay for... When a manufacturer designs a product the cost of production will include the acceptable tolerances and the tighter the more expensive. Additional quality control, QC, stops along the line add to the cost.
When that manufacturer contacts out production, the responsibility shifts and for small parts such as seatposts you can't inspect each one.
You get what you pay for...

[blasdelf]

Fizik Cyrano Alloy post is incoming.

Hopefully Alloy should be more consistent.

be sure to chop it down after you get it situated

with only 4" of it exposed you'll have at least 5" of excess in the frame beyond what's needed for minimum insertion

and that's a prime recipe for a stuck seatpost from galvanic corrosion!