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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 01-14-14, 11:48 AM   #1
MidnightAlchemy
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seat post right size, not fitting

Ordered a new seat post for an 80s Fuji Allegro I'm fixing up. Based on several posts on this forum as well as other google searches, I saw that it took a 26.6 diameter post. I even wiped away enough of the grit and rust on the old beat up one that came with it to see 26.6 faintly stamped.

Greased the seat tube, put a little grease on the bottom of post, and the thing barely will go in. Worried about forcing it too much… but is that ok? Any other tips?
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Old 01-14-14, 12:47 PM   #2
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If the seatpost had rust, there could be rust on the seat tube inside also. Try cleaning it thoroughly, and if the seatpost still doesn't go, lightly honing it. The seatpost should have a snug but not forced fit.
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Old 01-14-14, 12:55 PM   #3
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There's often distortion at the lug or top of the tube where it's slotted. Use a rat tail file to clean up the edges at the top of the tube,, and deburr the inside of the slot itself.

Where it's binding matters. If you can barely get it started, it's either burrs, or distortion and a bit of force on a well greases post will do the trick. However, it it gets about 2 inches in (below the slot) then starts binding, then other things are at work, possibly rut inside the tube as posted earlier.

If you own a power drill, scrounge or buy a length of metal rod as big as your chuck can handle. Cut a slot in one end, and slip in a strip of medium grit emery cloth, and twist it around grit side out. Put this into the seat tube, spin it and work up and down (do not remove from the tube under power), to clean up the inside. Ckean it all out grease the post and you should be fine.
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Old 01-14-14, 01:35 PM   #4
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Don't forget to clean and repack your bottom bracket after you grind and file in the seat tube.
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Old 01-14-14, 01:48 PM   #5
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Don't forget to clean and repack your bottom bracket after you grind and file in the seat tube.
Or do it with the bike upside down, so the debris falls out of the seat tube.
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Old 01-14-14, 03:39 PM   #6
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If you access an adjustable reamer ,
(maybe the reaming pinched spots will help, <blind Guess>)

I used 1 and took it out 0.2mm ID..
say, get a 26.8 post , a more common size it seems..

then you shave the ID to Just fit , the post you have on hand ..


IDK your bike situation 1st hand , so I'll just relay my project.. BS RB1 27.0, is now 27.2 .

like JDT says , angle the ST opening downward so cutting oil and chips fall out .

it was more wipe down the reamer and re oil, and shave a bit more..

I never made more than a few thousandths of a cut at any 1 pass because I wanted a clean Fit.

when done, very little clamping force is needed.
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Old 01-14-14, 03:49 PM   #7
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Quote:
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Don't forget to clean and repack your bottom bracket after you grind and file in the seat tube.
One handy DIY tool every bike mechanic should own is a balled rag or sponge on a string with a nut or weight on the end. You soak it in oil, and push it down the seat tube before doing any work there, throwing the nut in behind it. This keeps debris from falling into the BB. When finished turn the frame over so the nut falls out and pull out the rag out by the string to clean the tube.
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Old 01-16-14, 06:35 PM   #8
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Is there a slot in the seatpost lug? A turn of a flathead screwdriver might open it up just enough to slide the seatpost in.
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Old 01-16-14, 08:08 PM   #9
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One handy DIY tool every bike mechanic should own is a balled rag or sponge on a string with a nut or weight on the end. You soak it in oil, and push it down the seat tube before doing any work there, throwing the nut in behind it. This keeps debris from falling into the BB. When finished turn the frame over so the nut falls out and pull out the rag out by the string to clean the tube.
You see now, that seems obvious when I read it, but I'd never have thought of it on my own and would undoubtedly have ended up cleaning up a mess instead. Clearly you are from the old school of the mechanically inclined - my mechanically-brilliant father-in-law drops these kind of tidbits on me all the time. Is that just the voice of experience speaking, or is there some fantastic resource I can go read somewhere that will learn me up in these ways?
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Old 01-16-14, 08:20 PM   #10
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You see now, that seems obvious when I read it, but I'd never have thought of it on my own and would undoubtedly have ended up cleaning up a mess instead. Clearly you are from the old school of the mechanically inclined - my mechanically-brilliant father-in-law drops these kind of tidbits on me all the time. Is that just the voice of experience speaking, or is there some fantastic resource I can go read somewhere that will learn me up in these ways?
I came by this the old way, by stealing the idea. I used to play clarinet, and this is the basic design of a clarinet cleaner. Then it was simply a matter of seeing that something I used in another application could be adapted to this one.

I believe that the key to creativity is being open and seeing potential or something you can use in things totally unrelated to the immediate problem.

I'm also old school, where we weren't spoon fed solutions, but trained to think on our own.
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“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

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Last edited by FBinNY; 01-16-14 at 08:23 PM.
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Old 01-16-14, 09:08 PM   #11
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I'm also old school, where we weren't spoon fed solutions, but trained to think on our own.


..........Old School = Bigger Hammer
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Old 01-17-14, 06:36 AM   #12
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Love these outside-the-box ideas

I'm a software engineer and this applies so much to modern software development...
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