Tight seat post

[grateful]

I have two titanium frames that both take a 27.2 seat post. One frame is very tight to the point of scratching the post in a manner that is unacceptable. Do I have any options to increase the diameter of the seat tube? It should not take much as the post is able to be installed.

[colker]

I have two titanium frames that both take a 27.2 seat post. One frame is very tight to the point of scratching the post in a manner that is unacceptable. Do I have any options to increase the diameter of the seat tube? It should not take much as the post is able to be installed.

Ream the seat tube.

[R3awak3n]

My rock lobster is like that. Personally I rather it be too tight than not tight enough since that will more likely than not allow the seatpost to slip. As long as the post goes in I am ok with scratches. But yeah you could ream the seatube or lightly sand the post but then I guess different kind of scratches.

[bikeridah]

Maybe try some lube?

[grateful]

I greased the heck out of it. It is made of titanium and has a welded post clamp if that matters.

[batman1425]

What kind of post? There is some variability in tolerances and you might have a post that is on the big side of that range. Might try a different 27.2 and see if you have the same experience.

If so - as others have said ream it. Though I would throw a mic on there to see just how tight the fit is first before attempting to remove material from the frame.

[Peter P.]

You could buy a hone (https://www.mcmaster.com/hones) and smooth out the seat tube bore. It won't change the diameter, though.

You could also use some sandpaper to smooth over the sharp edges, including any vent holes inside the tubes.

Or, you could take the frame to one of the many framebuilders in Texas (https://forums.thepaceline.net/showthread.php?t=113817) and have one of them check the I.D. and remedy the situation if necessary.

As has been mentioned, the fault could lie with the seatpost. It's worth borrowing another 27.2 post and seeing if the problem persists.

[grateful]

I have tried a carbon and multiple Aluminum posts. All take a bit of effort to install.

[unterhausen]

I had a frame that was really tight. I used a flex hone on it and it's perfect now. Reaming is more difficult to get a good result and might thin things out too much without much benefit. At least that's the way I felt with my frame. Yours probably has some distortion from welding

The McMaster link above is for this hone: http://m.brushresearch.com/product-flexhone-tool.php

[bikeridah]

I have tried a carbon and multiple Aluminum post. All take a bit of effort to install.

I would just sand down a carbon post until it fits.

[colker]

I would just sand down a carbon post until it fits.

... or until it breaks. I would not take away any material from lightweight bicycle parts.
Reaming or honing the seat tube has no impact on longevity. JUst measure and keep measuring.
The seat tube probably has the wrong id.

[Brian Smith]

... or until it breaks. I would not take away any material from lightweight bicycle parts.
Reaming or honing the seat tube has no impact on longevity. JUst measure and keep measuring.
The seat tube probably has the wrong id.

I'd agree that most likely, if this titanium frame is a quality design with a proven design then the seat tube is likely under-reamed, particularly given the anecdotal evidence that multiple posts have been a struggle in attempts to fit them into the frame.
I would not agree, however, that reaming a titanium seat tube has no impact on longevity, and I would also disagree that sanding a similar amount of clear paint off a carbon seat post has a greater likelihood of leading to breakage than gaining the proper fit by removing titanium with a reamer.
Titanium seat tubes without thickened inserts at the seat cluster are particularly likely to deform during welding, and are particularly susceptible to weakening and shortened lifespan by a process of chewing the distortion away with a reamer.

[grateful]

the frame was constructed by one of the top ti manufacturers in the US if that adds to the discussion/recommendation.

[bikeridah]

... or until it breaks. I would not take away any material from lightweight bicycle parts.
Reaming or honing the seat tube has no impact on longevity. JUst measure and keep measuring.
The seat tube probably has the wrong id.

Have you ever perused weightweenies :eek:

Sanding off the clearcoat is worth a shot, I've done this myself with an Easton SP with no ill effect.

[vqdriver]

you could try the flex hone, but if it's really that tight, you could also just try a 27.0 post and see if that's too loose.

[grateful]

i prefer a shiny Nitto post, not sanding that down.

[unterhausen]

you could try the flex hone, but if it's really that tight, you could also just try a 27.0 post and see if that's too loose.

seems to me that scratching suggests the clearance is okay, the bore just needs to be shined up a little. Too bad the OP isn't nearby, I would let him use my flex hone. They aren't really that expensive. But I'm a little curious how a builder would let this go without fitting a seatpost.

[Peter P.]

But I'm a little curious how a builder would let this go without fitting a seatpost.

Here's one possibility-

From using their reference (seatpost, go/no go gauge, whatever) for hundreds, if not thousands of frames, its O.D. has become worn and undersized.

It pays to check your tools occasionally.

[oldpotatoe]

I have two titanium frames that both take a 27.2 seat post. One frame is very tight to the point of scratching the post in a manner that is unacceptable. Do I have any options to increase the diameter of the seat tube? It should not take much as the post is able to be installed.

Take a flexhone to it..particularly if the post is getting scratched..might be a burr where the seat stays connect to tube.
And for right below..that seattube pst flexhone gets HOT...so watch that...

[unterhausen]

btw, a 1 1/8" flex hone works for 27.2mm posts. It's a little annoying to insert. the first couple of times

[charliedid]

Just to be pedantic:

Reaming is an operation performed after drilling a hole in a work piece. This is done to remove the slight irregularity in the drilled hole and making it perfectly round.

Honing is a surface finishing operation that gives very smooth inner surface usually required for frictionless relative motion between two parts.

[benb]

I have this issue with my All City Space Horse... it's steel & I have a Specialized Carbon post in it... it's one of those Carbon posts with the leaf spring shock mechanism in it.

I haven't sanded the post.. but I'd much rather sand the post than mess with an expensive frame. Custom Ti frame is probably > $3000 and you'd rather mess with that than a Post that cost $100-200?

If it's a carbon post who the heck cares, it's going to get scratched/polished within one season if you attach a tool bag to the saddle. You ought to be able to lightly sand the post *below the insertion point* and you'll never see the scratches.

In my case I 100% don't think it's a frame problem, because I have put numerous other posts in that frame and none of the others had the issue... the Specialized post is the one that is slightly larger than it's supposed to be.

I got the post set where it needs to be and don't mess with it... so I am not doing anything about it. But it's quite hard to adjust if I actually needed to.

[cmg]

It could be that the seat post is slightly larger than 27.2. Campy posts are closer to 27.3 for example. Ream the seat tube, doesn't sound like you'll need to take off very much material.

[seanile]

Reaming is an operation performed after drilling a hole in a work piece. This is done to remove the slight irregularity in the drilled hole and making it perfectly round.
it's also what's done to seat tubes after welding twists the metal out of round.

[grateful]

Would your average shop be capable of this surgery?

[DRZRM]

I had a ti frame from a well known frame builder that did the same thing. Although some 27.2 posts would go in, the Moots I wanted to use and a Thomson I had around would not. The builder offered to hone it himself if I wanted to ship (mind you I bought the frame second hand) but suggested I have a local shop to it. He spoke directly to one of their mechanics and it was dealt with in about 15 minutes of waiting. Perfect fit.

[unterhausen]

I'm not sure what the point of pedantry is regarding this subject. A hone removes a lot less material and is significantly less likely to cut through a tube. But it sounds like that's what is needed here, not reaming. And a hone works a lot better in a tube with a slot cut in it.

I'm pretty sure there are shops that have reamers that have no business having a reamer. Do you know if the seat tube is externally butted or has a welded seat collar on it? https://www.paragonmachineworks.com/frame-building-parts/miscellaneous.html?cat=197

A seat collar is much less likely to be distorted, but also has a lot more thickness so reaming would be safer. You can tell by looking for a weld a couple of inches from the top of the seat tube.

[tctyres]

btw, a 1 1/8" flex hone works for 27.2mm posts. It's a little annoying to insert. the first couple of times

What grit do you recommend? They have 120, 180, 240, 320, 600, and 800. I was going to guess 320, as I have a seat tube to clean up.

[unterhausen]

I have a 240 grit. Not sure if that's the best one or not. It leaves a nice smooth surface on steel. Depending on the defects you want to remove, I don't think you will be particularly happy with 320 grit. I might get another that is coarser. It doesn't remove much material

[grateful]

The frame is made by Moots and has an integrated seat binder welded in place. It sounds to me like honing is the way to go. I don't think it would take much but I don't want to remove material if possible.

[tctyres]

I have a 240 grit. Not sure if that's the best one or not. It leaves a nice smooth surface on steel. Depending on the defects you want to remove, I don't think you will be particularly happy with 320 grit. I might get another that is coarser. It doesn't remove much material

Thanks for the feedback :beer:

[SPOKE]

Flex hone is what you need. I keep one in my tool stash. A flex hone spun in a hand drill will deburr and smooth the seat tube ID. You will get a very small diameter increase if you get too carried away with it.

[grateful]

Is honing something that the typically shop is capable of?

[vqdriver]

Call up your local shops before taking your bike in. Some shops do Flex honing, Dropout alignment, rivnuts, Etc. Other shops don't do any framework

[HenryA]

Might also look at a brake hone. Its more likely to give you a straight and cylindrical bore inside the tube.