WHAT tools do I need to remedy a tight fitting seat post.
and yes is the right size for the frame
27.2 in a cannondale.

Provided it's a non-carbon fiber seatpost, how about just applying a little grease to it (and cleaning out the seat tube before reinserting the post)?

Maybe a little sandpaper? You probably just need to take it down a couple of microns.

at our shop we have a tool that goes in a drill and has balls of abrasives on the end of wire and you just spin it in the seat tube and it takes just enough material out to fit ill-fitting seat tubes.

I use a brake cyclinder hone in a drill to clean up seat tubes. Basically what was said above. Roger

At the risk of asking a naive question, though: it would seem that one of the pieces (seatpost, seat tube) or both are out of round.

If the TUBE was a pretty clean 27.2, then I'm not sure I'd want to hone it out (oversize it) unless I intentionally moved up to the next stock diameter of post. Otherwise, replacing the post WITH a new 27.2 might involve a too-loose fit situation.

That's why -- if I couldn't verify which one WAS actually off -- I'd probably work the post.

Thoughts?

grease the post?

I'd suggest first checking that the post is good by trying it with a different 27.2, preferably a new one. Then try to see if the seattube is out of round, perhaps by using caliper measurements at different points. If it is, you need to decide if the frame is damaged and unsafe. If not, you could use a ball style hone, to clean-up the seattube, as suggested by someone above (the thing with the balls). Then grease it up and you should be good.

those things work pretty good, I used them before

If it is a carbon post, sometimes the clear coat puts the diameter just a little outside of the specs.
Measure post and frame to see which is out of spec.
If seatpost, try very fine grit wet sandpaper till it fits.
If frame, have it reamed to proper size.

Buy a vernier caliper, costs less than $10 and you can measure the seat post and seat tube for out of round. Very handy tool, I use it all the time to measure chain wear.

yeah, I would'nt want to go in there and ream, or resize a seat tube, especially with a drill motor and abrasive balls. I also dont think the seat tube or seat post is out of round. If there's any discrepency I would think it would be in the seat collar area where it tightens against the post. Either that or its corroded inside the seat tube. After years of tightening and re-tightening it could've gotten slightly out of round right there at the point.

I would try taking an old spoke with the j-bend end bent tight onto a rag soaked with "pb-blaster". Ball the rag up to where it fits firm inside the seat tube and swab out the seat tube. The pb-blaster will clean up any corrosion inside the seat tube. I would do that first before permanently altering the internal deminsions of the seat tube with abrasive balls.

Some of those reaming tools are light enough to just take out burrs and imperfections. If you only run it for a few seconds, it won't do damage and will just leave it smooth. there are often burrs around the slit in the seat tube where the clamp holds the post. If you run it down the seat post for minutes on end, you'll be taking out a considerable chunk of frame metal.
If you're seriously worried about reaming, then try to find a light wire brush that will fit your drill, one without the extra knobbies on the end of the wire.

I cleaned paint out of the seat tube of a newly painted frame by wrapping 60 grit sandpaper around a rod that just fits the seat tube and rotating by hand.

Had a problem like this with an old steel frame on which someone had overclamped the fastback bolt. Had to ream to get the new post in. Probably not your problem, but reaming works nicely. I'd try everything else first, though.

Reviving an old post here, but i think i'll have no choice but to ream my seat post tube if i don't want to go the spacer route.

My bike is a 1987 Schwinn Cimarron MTB, and the Nitto seatpost already there measures 1.045 inches on my quality Starrett dial caliper. That equates out to 26.543mm on a google inch to mm converter,.....not a standard size today.

I've ordered the closest Cane Creek Thudbuster LT suspension seatpost, which i expect to be too tight to use when it arrives. It's supposed to come in measuring 26.8mm

Cane Creek does make one smaller diameter Thudbuster LT seat post that i could have ordered, but i would have had to use a spacer to make up the difference,....not what i wanted to do.

I looked inside my seat post tube on the bike, and it looks like there is paint along all the area i could readily see. I'm expecting that when i pick up a brake cylinder hone i should be ably to remove the paint and primer layer to remove approximately .25mm in thickness needed for a proper fit.

That's not very much, .....and even if a little of that is steel from the tube i'm confident the chromoly frame won't mind!

As i plan to keep the inside of the tube well greased,.....rust formation shouldn't be a problem.

....any thoughts on anything i might be missing?

BTW, if you own a Thudbuster, you might be interested in this idea i have to get proper fitting dust covers fitted to the bushings.

I started a post here on that: https://www.bikeforums.net/showthread...l-Tube-Bushing

Don't mess with the seat tube until you try another 27.2 seatpost.

If it still fits tight you have a choice of enlarging the seat tube or trying a 27.0 seatpost.

I think I'd do the 27.0 seatpost.

get a ball burnisher.. they look like a small stalk of carborundum brussels sprouts.

chuck it up in the drill and run it in and out , that should take off burrs
from the cursory reaming at the factory.. then a little grease.

Not sure why you're responding to the FIVE YEAR old original posters's question rather the followup one i asked just 1 post before your response when i revived this old thread?



But,.....the 27.0 post is still bigger than i need,....and not even made in that size for the Thudbuster i don't believe. (and bigger than the 26.8mm Thudbuster LT i have coming)

Regardless, i think .25mm can be done with mostly removing the paint/primer layer in the seat post tube.

....never heard of the "ball" type hone though,....thought a brake cylinder hone would be my only option.

Prior LBS I worked in , 25+ years ago, quick pass with the ball burnisher
was done with every steel framed bike assembled.


[Why, ? someone brings a post up to the top of the list,
then its up where it can be seen again]

[NB Job, was earlier than Wasniak&Jobs, computer peeps]