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Cutting headtube / reducing stack height

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Cutting headtube / reducing stack height

Old 10-12-20, 07:43 AM
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theblackbullet
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Cutting headtube / reducing stack height

Hello, I am looking into the possibility of modifying a Soma Buena Vista frameset to reduce the stack height. The headtube on the 62cm frame measures 230mm, I'd like to get it to 210mm or less if possible. Is there any reason why this headtube cannot be cut down. It looks like the headtube has thicker bands at the top and bottom of the tube. Do these serve as a necessary reinforcement or are they more ornamental?

I don't have the frameset yet. I am just dreaming in my head. I'm tall with a long torso, so finding a mixte frame that can fit me is near impossible. In a perfect world I would have the stack of the 58cm and the reach of the 62cm Soma.

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Old 10-12-20, 08:21 AM
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The rings serve as a reinforcement for the headset. If you were to cut past the top ring you risk the headtube cracking over time. Could you get the 58 and run a longer stem or bars with more reach?
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Old 10-12-20, 08:43 AM
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Originally Posted by 8aaron8 View Post
The rings serve as a reinforcement for the headset. If you were to cut past the top ring you risk the headtube cracking over time. Could you get the 58 and run a longer stem or bars with more reach?
to get the desired reach on the 58 frame would require a 140+ stem. I've never liked the way anything handled with longer than a 130mm.

I suppose something like this could be added after the fact?
https://www.cycle-frames.com/1-1-8-HEAD-TUBE-RINGS.html
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Old 10-12-20, 08:57 AM
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Yes, a ring could be added pretty easily.

Before going down that road I'd chop the steerer tube and get rid of all the spacers. Another option to lower the bars would be get a -17 degree stem.
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Old 10-12-20, 10:58 AM
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Seems for that style of bike it would make more sense to just leave it and manipulate things in other ways.
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Old 10-12-20, 11:02 PM
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are those measurements after you remove the 6cm of spacers?

Those rings only work if they are brazed on, so that means new paint.
The upper ring is less important than the lower ring. So depending on how thick the head tube tubing is, the top ring might not be strictly necessary.
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Old 10-13-20, 07:25 AM
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Originally Posted by unterhausen View Post
are those measurements after you remove the 6cm of spacers?

Those rings only work if they are brazed on, so that means new paint.
The upper ring is less important than the lower ring. So depending on how thick the head tube tubing is, the top ring might not be strictly necessary.

As well as how tight the upper headset cup is pressed into the head tube end. I forget where or with which brand but I do recall frames being reamed to have a non interference fit with the cups. The cups were to be lock tighted in place.

With a view to how the upper cup fits I would have little concerns about cutting down the head tube on this bike. However do think about the reversible options first. Cutting off some part of a frame is often regretted later. Andy
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Old 10-13-20, 11:42 AM
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The headbadge will not be centered on the head tube, so you can't cut it.

It looks like the head tube is really long, but the top of the head tube is even with the top of the seat tube. So it's actually a little lower than typical nowadays for threadless steerer bikes. That's something to consider on a bike that you might not keep forever. Lots of people would want more stack height
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Old 10-13-20, 07:03 PM
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You can cut the headtube but you will need to ream the id of the HT to fit the bearing cup. This might make the wall too thin and crack easily. If you aren't sure if it will be a long term frame and aren't worried about it potentially cracking in the future you can buy a reinforcing ring and epoxy it on and get some matching model paint and paint the ring. If it is long term have the ring brazed and a pro repaint.
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Old 10-13-20, 08:08 PM
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I would cut the HT at the top, after confirming that the tube ID will be in the ballpark after cutting, to where it only needs a little reaming (as is usually the case). No qualms about that at all. I used to make lugless bikes with thin 1-1/4" head tube, brazed on ring at the bottom, no ring at the top. No one ever had a problem with the top of the HT wallowing out or cracking.

I suppose if the HT is thinwall and low-strength tubing, you may have a problem, but even then I doubt it. But my frames with no ring at the top were always 531, Cyclex, or domestic generic 4130 "aircraft tubing". I never tried it with Hi-Ten or lower quality tube. Do we know what your frame is made from?

Do you know someone who can ream and face the HT after you cut it? LBS, local framebuilder or extreme nutcase like me who just happens to have a HT reamer?

I didn't see any mention of where you are I always encourage people asking questions like this to include their city/state so we can point you to someone local to you.

Mark B in Seattle
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Old 10-14-20, 04:43 AM
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location says "Georgia" so I'll assume U.S.
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Old 10-14-20, 12:57 PM
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Originally Posted by unterhausen View Post
location says "Georgia" so I'll assume U.S.
d'oh!
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