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  1. #1
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    New question here. Boring a Tapered headtube bottom flange to taper?

    So my bike looks like it has a tapered headtube - so I went and bought an upgrade fork than has a tapered steerer.

    Taking a closer look at the headtube, there appears to be a flange on the bottom to fit a 44mm headset bottom cap - which I find rather strange.

    I am aware that there are headsets available for 44mm to 1.5" tapered steerer - but I would rather not fit a traditional headset since this will further lift the front of the bike (the upgrade fork is longer already, I wanted to change the geometry a little on purpose)

    So the question is - can I machine out the flange without destroying the frame?

    Here is kinda what the headtube looks like
    Name:  headtube.png
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    The bike is a Scott Spark 29er Team, 2012

    Should the headtube be butted, or is it usually just straight tube?
    Knowing that the resulting ID of the headtube may differ to standard, a custom bottom cup may be required, which I am ok with.

  2. #2
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    This is a great idea. You should totally bore out your headtube. Good things will follow.
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  3. #3
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    Probably won't destroy it, but might make it useless.

    No offence intended, I think I understand "what" you are trying to do, but I can't figure out why. Can't you change geometry of the bike without modifying the frame? I would rather modify the fork (internal spacers) or some other removable piece.

    I would imaging that Scott put many hours and many $$$ to design and engineer the frame, but it's your bike, do what you want.
    How can anyone who's been riding as long as I have, be so slow???

  4. #4
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    Quote Originally Posted by Silentfoe View Post
    This is a great idea. You should totally bore out your headtube. Good things will follow.
    Will do it tonight then

  5. #5
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    Quote Originally Posted by Rock View Post
    Probably won't destroy it, but might make it useless.

    No offence intended, I think I understand "what" you are trying to do, but I can't figure out why. Can't you change geometry of the bike without modifying the frame? I would rather modify the fork (internal spacers) or some other removable piece.

    I would imaging that Scott put many hours and many $$$ to design and engineer the frame, but it's your bike, do what you want.
    So what I am trying to do is remove the flange that has been left in a tapered headtube so that the headtube can actually take a tapered steerer

  6. #6
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    Are you sure that it won't take a tapered steerer? I thought they came with straight steerers, but would take tapered as well. This article seems to suggest so, but I haven't found definitive specs.

    But in any case, don't go boring out your headtube.

    Edit: Here's the 2012 Spark manual. It's not model specific though and the headset info says it differs by model. It seems very possible though that you have something like a press fit reducer on the bike now to run the straight steerer. I'd ask your shop if you can't tell.

  7. #7
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    Quote Originally Posted by MarcusBrody View Post
    Are you sure that it won't take a tapered steerer? I thought they came with straight steerers, but would take tapered as well. This article seems to suggest so, but I haven't found definitive specs.

    But in any case, don't go boring out your headtube.

    Edit: Here's the 2012 Spark manual. It's not model specific though and the headset info says it differs by model. It seems very possible though that you have something like a press fit reducer on the bike now to run the straight steerer. I'd ask your shop if you can't tell.
    Thanks for the links!

    Had a look through the manual, like you said there appears to be 2 variations on the headsets. One being tapered, the other 1 1/8 straight. In both cases the headtube looks like its tapered.

    On closer inspection, mine appears to not have a reducer per se, but the headtube itsself has a flange on it that acts as a reducer - the hole at the bottom of the headtube is 44mm (same as the top)

    The headtube appears not be just a tube, but rather a tube with the bottom bent in again to form a reducer. The diagram in my 1st post shows a cross section of the headtube only

    Hope this makes a little more sense!

  8. #8
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    Quote Originally Posted by Danielmessem View Post
    Thanks for the links!

    Had a look through the manual, like you said there appears to be 2 variations on the headsets. One being tapered, the other 1 1/8 straight. In both cases the headtube looks like its tapered.

    On closer inspection, mine appears to not have a reducer per se, but the headtube itsself has a flange on it that acts as a reducer - the hole at the bottom of the headtube is 44mm (same as the top)

    The headtube appears not be just a tube, but rather a tube with the bottom bent in again to form a reducer. The diagram in my 1st post shows a cross section of the headtube only

    Hope this makes a little more sense!
    I am not familiar with that frame, but is there a chance that there is some sort of insert/reducer that has been painted over to make it look like one single piece? Maybe poke a broom handle through your head tube and whack the flange/reducer with a mallet to see if it comes out.
    I would not recommend irreversible changes to your frame. Removing a lot of material would probably greatly weaken it.

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  9. #9
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    Good idea, just tried that out, unfortunately it appears to be part of the headtube - however the bottom section is quite thick, which is good

    Boring a Tapered headtube bottom flange to taper?-magnifier_20140702_190245.jpg

    Click image for larger version. 

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    Attached Thumbnails Attached Thumbnails Boring a Tapered headtube bottom flange to taper?-magnifier_20140702_190636.jpg  


  10. #10
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    I don't think there's ever a time when it's a good idea to modify a head tube. A head tube failure could easily put you in an ambulance.

    In my opinion, if there were no way to make it work without cutting into the frame, I would sell the tapered steer tube fork and buy a straight steer tube fork.

    Safety issues aside, even if you got it to work and it never failed, I bet it would be prone to creak, bind, be out of alignment, etc.
    '12 Santa Cruz Superlight 29 | '12 Santa Cruz Butcher | '06 Specialized Allez Comp | '81 Schwinn Converted Fixie

  11. #11
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    Instead of getting random internet answers, maybe try a store that sells scott bikes or bike company itself?

  12. #12
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    I am in touch with scott, taking up the issue that the bike was advertised as having a tapered headtube while it really has a straight one

    As for posting on the forum, I found a nice thread simular to this which led me to believe that I may get an answer from someone with experiance doing simular things DIY Tapered Headtube Mod Project

  13. #13
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    Unless Scott gives you a new frame, you seem hell bent on messing up a perfectly good one.

    Good luck to you Dude, you'll need it.
    How can anyone who's been riding as long as I have, be so slow???

  14. #14
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    thats why I shop on amazon or rei... I just simply return the tapered fork for a straight one...

    Wouldn't that be the solution ? can you get a refund on your fork ?
    fat old man ... fueled by Mexican pastries....

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    Quote Originally Posted by MtbAZ44 View Post
    thats why I shop on amazon or rei... I just simply return the tapered fork for a straight one...

    Wouldn't that be the solution ? can you get a refund on your fork ?
    Perhaps if he has not modified the fork, the manufacturer would be willing to swap out the CSU for a straight 1.125".

  16. #16
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    The difference between a Cane Creek 40 external cup lower (to fit a 44 diameter headset and 1.5" steerer) and a zero stack lower is 8mm. If you are worried about raising the front by that much, you could shorten the fork travel by the same amount and keep the same basic geometry. Sounds a lot better than trying to machine your headtube...

    You would need a Cane Creek ZS44|EC44/40, Chris King InSet 7, or equivalent.

  17. #17
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    (edited based on new information)
    Last edited by .WestCoastHucker.; 07-03-2014 at 01:10 PM.


  18. #18
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    Your pictures are a little confusing, but I think I'm looking at a head tube with a headset installed. Can you post some pics that aren't so zoomed in, so there are some references for scale and orientation?
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  19. #19
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    What would you even bore it out with? Are you gonna fix your bike frame on a milling machine or something? Even that wouldn't be easy.

  20. #20
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    Quote Originally Posted by Kanik View Post
    What would you even bore it out with? Are you gonna fix your bike frame on a milling machine or something? Even that wouldn't be easy.
    Yes, milling machine with a boring head. Agree that securing it would be tricky, was thinking of taking only the front triangle and securing/aligning it with some sort of jig

  21. #21
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    Thanks for all the feedback - here is some more info

    Quote Originally Posted by AndrwSwitch View Post
    Your pictures are a little confusing, but I think I'm looking at a head tube with a headset installed. Can you post some pics that aren't so zoomed in, so there are some references for scale and orientation?
    Thanks for taking the time to give that feedback, hopefully these pics are better:

    Side view, front view
    Front top with headset installed, ID=44mm, OD ~50mm
    Bottom view with internal headset cup installed: id=44mm, OD ~65mm

    Boring a Tapered headtube bottom flange to taper?-20140703_092141%5B1%5D.jpgBoring a Tapered headtube bottom flange to taper?-20140703_092151%5B1%5D.jpgBoring a Tapered headtube bottom flange to taper?-20140703_092213%5B1%5D.jpgBoring a Tapered headtube bottom flange to taper?-20140703_092202%5B1%5D.jpg

    Appreciate all the frank feedback - In no rush to fit the new fork.
    The 44mm to traditional 1.5" cup is the easy solution, and 8mm is probably ok for geometry - can always give it a try.

    Boring the bottom of the headtube would be an additional 'project', something nice to do.

    From what I understand, this frame came in a version with the same headtube already bored out at the factory - not something that I just want to do without getting as much information as possible.

    While I accept the risks, I would rather learn from others than learn by breaking a perfectly good frame.

  22. #22
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    It sure does look like you could punch out that insert.

  23. #23
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    From Park Tool, the Onepointfive standard has cups that press into a head tube dia of 49.6mm. If your current bore on the bottom there is for 44 (actual 43.9), I don't see why you couldn't bore out 5.7 mm. It doesn't look like it would make the head tube excessively thin, because it looks like the head tube is made to be bored for either 43.9 or 49.6 mm, and in this case the bike build was able to get away with a 1 1/8 fork and semi-integrated headset, so they just bored it for 43.9 and did that.

    I say do it. Hah. Something like this isn't as stupid as some of these people might make it to be, but I'd reckon most of them wouldn't be able to machine it themselves anyway.

  24. #24
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    Quote Originally Posted by Kanik View Post
    From Park Tool, the Onepointfive standard has cups that press into a head tube dia of 49.6mm. If your current bore on the bottom there is for 44 (actual 43.9), I don't see why you couldn't bore out 5.7 mm. It doesn't look like it would make the head tube excessively thin, because it looks like the head tube is made to be bored for either 43.9 or 49.6 mm, and in this case the bike build was able to get away with a 1 1/8 fork and semi-integrated headset, so they just bored it for 43.9 and did that.

    I say do it. Hah. Something like this isn't as stupid as some of these people might make it to be, but I'd reckon most of them wouldn't be able to machine it themselves anyway.
    From the manual the same headtube comes with either 44mm or 54mm bore - so thanks, thats the confirmation I was looking for.

    Is there anything special about boring a heatube?

    Of course alignment and final measurements will need to be spot on

  25. #25
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    Well on doing some more research, it looks like that 49.6 mm is also for an external cup. I think it would raise the stack less than the one for 44 but maybe not much. The fully integrated headsets for 1.5 steerer is 52 or 54 mm dia, which is maybe pushing it on this head tube. You would have to do the measurements and judge for yourself. Really, I say just keep it at 44 and use the headset for that diameter unless you really trust your judgement.

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