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  1. #1
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    Anyone ream out the seat tube to 30.9 for adjustable posts?

    As title states... my 6 Point is in desperate need of a KS 900!

    Have FUN!

    G MAN
    "There's two shuttles, one to the top and one to the hospital" I LOVE this place!!!

  2. #2
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    Oh man!...My MKIII comp needs a Joplin 4...but I just couldn't bring myself to ream the .45mm out of the seat tube, it's wall being only about 2mm itself...I was looking for a KSi950 too but no Aussie distributor...and my mate and I got a good deal on 2 Jop 4's...but I took mine back to the shop....

    But, would it be dangerous,?...the inherent strength of the tube shape should hold up...and wouldn't a stiff post in the tube add strength?...I don't really know...so I chickened out...

    I'll be watching this thread with interest

    Good luck mate...

  3. #3
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    I don't see how doing this, even with local Hardware Store material, would be bad considering the amount of material needing removal. 1/4 or 5/16" non threaded stock @ 2ft, lengths of Belt-Sander sandpaper in 100-400 Grit, and cutting a gap in the end this rod. Tighten a wrap of the cut sanding belt, and run a low-speed drill with the Coarse, finish-sand with 400 grit or higher depending. Should be a non-issue. I'm keeping my rigid seatpost though.

  4. #4
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    Not like it'll void your warranty.
    Sent from the future to destroy the past.

  5. #5
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    go ahead. it won't crack at the seat tube anyway.

  6. #6
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    Quote Originally Posted by Gman086
    As title states... my 6 Point is in desperate need of a KS 900!

    Have FUN!

    G MAN
    I have to admit when I first read this I didn't think it was a good idea but I now I get it. Look at all of the other bikes with a 30.9... they all run a 34.9 clamp, same as the 6 point. Thinking back, I actually had a bike with a 31.6 seatpost which meant the walls were even thinner. I am totally down for this mod, but what is the best way to do it?

  7. #7
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    ...personally, if I was to have it done, I'd take the frame to an engineering workshop and have it done precisely...preferably by a German engineer of advanced age...

  8. #8
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    You realize only the first 3-4 Inches of the SeatTube are 30.9mm, right?

  9. #9
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    Quote Originally Posted by Uncle Jemima
    You realize only the first 3-4 Inches of the SeatTube are 30.9mm, right?
    what?

  10. #10
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    What what? If the length was entirely 30.0 to the BB Juncture, the seat post would slip when clamped. It would be flare right at the Clamp. The Seat-Tube sees a very slight taper, and tooling it .45mm a side larger is not going to create anything in slippage issues; a 31.6mm FSA post though? Never. Return the metal to nearly as smooth as it is, if not smoother. I'd say if could be done, but I have no want or need for a bouncy seatpost.
    You are going to keep this post rigidly in-place anyway, because it is self-adjusting. A bolt-style clamp will afford better retension then a QR-style.

    Quote Originally Posted by saturnine
    what?

  11. #11
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    Quote Originally Posted by Uncle Jemima
    What what? If the length was entirely 30.0 to the BB Juncture, the seat post would slip when clamped. It would be flare right at the Clamp. The Seat-Tube sees a very slight taper, and tooling it .45mm a side larger is not going to create anything in slippage issues; a 31.6mm FSA post though? Never. Return the metal to nearly as smooth as it is, if not smoother. I'd say if could be done, but I have no want or need for a bouncy seatpost.
    You are going to keep this post rigidly in-place anyway, because it is self-adjusting. A bolt-style clamp will afford better retension then a QR-style.
    I've read your post a couple of times and I still have no idea what you are talking about.

  12. #12
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    There is a response above that prompted it. Very slightly the I.D. of a Seat Tube will grow as it reaches the Bottom-Bracket juncture. The design affords it. How long is one of these that only will rest in the Seat-Tube anyway? No more than 5-6 inches, and that is where most the compression-fit is natural. I thought at nite, and perhaps some Mountain Bikes would have absolutely straight tubing. People shim posts all day, and they hold. I am not saying this cannot fail, but taking it from 30.0 to 30.9mm is not a ridiculous idea. If if bothers still, put a dowel end in one end of the post, and run a belt-sander on that.

  13. #13
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    Why not get a Gravity Dropper and a shim?

  14. #14
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    Because my 6 Point needs and offset post - no ifs ands or buts about it!
    Last edited by Gman086; 09-17-2010 at 12:53 PM.
    "There's two shuttles, one to the top and one to the hospital" I LOVE this place!!!

  15. #15
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    Quote Originally Posted by Gman086
    Because my 6 Point needs and offset post - no ifs ands or buts about it!
    Here you go GMAN. When you are done using it... send it to me!

    http://www.chadwickreamers.com/angle...ure=fractional
    You need size 29.

    Here are some instructions...
    http://mountainbikers.hubsystems.com...s/chapter7.pdf

  16. #16
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    Quote Originally Posted by wormvine
    Here you go GMAN. When you are done using it... send it to me!

    http://www.chadwickreamers.com/angle...ure=fractional
    You need size 29.

    Here are some instructions...
    http://mountainbikers.hubsystems.com...s/chapter7.pdf
    AWESOME!
    "There's two shuttles, one to the top and one to the hospital" I LOVE this place!!!

  17. #17
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    Because my 6 Point needs and offset post - no ifs ands or buts about it!
    Fair point.


    Looked at those instructions and noticed it said it wasn't designed to allow a larger size post to fit and if used to do so "the job would take an unbelieveably long time to complete".

  18. #18
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    I know people have successfully shaved 30.9 Kindshock I900 to 30mm diameter. Only the bottom 2cm are delicate. I'ld probably think best grind down on both and settle with 30.5mm..

  19. #19
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    This is going to be the best-bet. I actually went and 'wiggle' tested my bikes, and there is different give within the Seat Tube on each.
    If this Seatpost does come apart, it should, get an aluminum rod from Hardware Store and find a Wood Working Shop with a stationary belt sander. Throw some belts at them and ask for them to knock it down by spinning it on the Rod. If you have the ST be symetrical with the post, it will crack. Smoothing the post to a thinner Diameter sounds fine.

    Quote Originally Posted by extremecarver
    I know people have successfully shaved 30.9 Kindshock I900 to 30mm diameter. Only the bottom 2cm are delicate. I'ld probably think best grind down on both and settle with 30.5mm..

  20. #20
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    Quote Originally Posted by wormvine
    Here you go GMAN. When you are done using it... send it to me!

    http://www.chadwickreamers.com/angle...ure=fractional
    You need size 29.

    Here are some instructions...
    http://mountainbikers.hubsystems.com...s/chapter7.pdf

    My LBS has one... I am tempted.

    What about the stress riser as someone mentioned? Any engineers in the house? I do not doubt that this process will result in a weaker seat tube, but realistically how big of a deal is it?

  21. #21
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    Quote Originally Posted by ride_nw
    My LBS has one... I am tempted.

    What about the stress riser as someone mentioned? Any engineers in the house? I do not doubt that this process will result in a weaker seat tube, but realistically how big of a deal is it?

    Regarding the "stress rider" mentioned in the pdf.
    I doubt it would affect it at all in respect to the 6point. The rocker links mount to a bracket that surrounds the tube. This adds strength to the tube. The short support tube that connects the top tube to the seat tube also adds a decent amount of support. Remember the 6point's seat tube is thicker than the standard 30.9 seat tube.
    In comparison, The 09' Reign my wife has uses a hydroformed bulge that has a sleeve piercing it for the rocker bolt. That is why there is a limited insertion depth of the seat tube. A common complain of Giant Reigns. There is also a little lip of aluminum inside the tube left over from the final reaming of the hydroformed tube. If giant isn't worried about this lip, I wouldn't worry about it.

    I will probably try this in the Spring before the season opens up for me. I will post up the results if/when it happens.

  22. #22
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    Quote Originally Posted by wormvine
    Regarding the "stress rider" mentioned in the pdf.
    I doubt it would affect it at all in respect to the 6point. The rocker links mount to a bracket that surrounds the tube. This adds strength to the tube. The short support tube that connects the top tube to the seat tube also adds a decent amount of support. Remember the 6point's seat tube is thicker than the standard 30.9 seat tube.
    In comparison, The 09' Reign my wife has uses a hydroformed bulge that has a sleeve piercing it for the rocker bolt. That is why there is a limited insertion depth of the seat tube. A common complain of Giant Reigns. There is also a little lip of aluminum inside the tube left over from the final reaming of the hydroformed tube. If giant isn't worried about this lip, I wouldn't worry about it.

    I will probably try this in the Spring before the season opens up for me. I will post up the results if/when it happens.
    Cool, thanks for the reply. My gut instinct says it shouldn't be a problem. I am not in a big hurry, I will probably do it sometime over the winter as well.

  23. #23
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    my banshee rune has a 30mm seat tube as well. i pm'd keith the banshee engineer and he said the new seat tubes are 30.9 id but the same od so making mine 30.9 would not weaken it beyond what it is designed to do. the problem was that the frames are heat treated and hard enough that they will chip when reaming not cut smoothly. he said it could be done with care but he wasn't promising success. i have been waiting to see the shop guy from one of the machine shops we deal with at work to ask him about it. want to do the reaming but i am a little leery

  24. #24
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    Good info everyone! Now who's gonna go first?!

    Cheers,

    G
    "There's two shuttles, one to the top and one to the hospital" I LOVE this place!!!

  25. #25
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    Not it!

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