# If a threaded steerer tube is long enough...



## Ride-Fly (Mar 27, 2002)

can one use a threadless stem, granted with a threadless headset? 

I ask because, I found a steel frame that I may buy that has a lot of (threaded) steerer tube left. I was wondering what prevents me from using a threadless stem with the existing threaded area of the fork.

I much prefer a threadless set-up to the old-school quill stem.

Has anyone ever tried this set-up?

Thanks,


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## SilverStar (Jan 21, 2008)

If you try it, and the stem clamps onto the threaded portion, you really run the risk of snapping the steerer. I've heard tales of folks who have done the threadless-on-threaded fork trick, but the successful ones have had enough extra steerer that they could cut off the threaded portion and still have enough unthreaded part left over to clamp the stem to.


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## RHankey (Sep 7, 2007)

I would not do that. Threaded forks are not designed to take much in the way of stress in the threaded portion of hte steerer tube. The wall thickness of a threaded steerer tube, measured form the deepest part of the thread, is much thinner than any threadless steerer tube. Furthermore, the threads could likely cause the stem to break as well. Swap the fork for a threadless one, find a quill stem arrangement that you can live with the looks of, or let someone else who still apprecaites quill stems enjoy the frame.


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## logbiter (Sep 14, 2005)

agree with others. From what I understand, the threaded portion can break and the threads can cause issues with the threadless stem.
I've done it with a few mtn bikes, but I only used it offroad when the stem clamp bolts were below the threads. On the forks I've done it with, I measured the wall thickness of the steerer tube to make sure it was as thick or thicker than the threadless.


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## brianmcg (Oct 12, 2002)

Yes, it would be much easier to just get the proper stem and headset, otherwise buy a different bike.


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## aaronbarker (Aug 31, 2005)

One other option is to add a threadless quill adapter. That's basically a quill stem without the stem - a cylindrical extension with an area to clamp a threadless stem. It spreads any bending forces across a larger area of the steerer thus eliminating any concentrated forces that might cause a catastrophic failure. The downside is a little extra weight and you're bars might be higher than you'd prefer but that is probably a minor trade-off.

have fun,
aaron


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## Scooper (Mar 4, 2007)

Not a good idea, although I've heard of some who braze over the threads with brass (not silver) to strengthen the threaded part of the steerer, filed the excess brass even with the major diameter thread crests, and have successfully run threadless stems on steerers so modified. It wouldn't be as strong as if it had never been threaded, but stonger than if the threads were left unfilled.

Caveat emptor; do this AYOR.


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## FBinNY (Jan 24, 2009)

The critical issue is where the last thread is. If the thread ends well into the stem, and is not cut undersized compared to the unthreaded portion, you can go ahead and use it.

What you absolutely cannot do is use a threaded steerer with any thread extending below the stem, or even close to it's bottom. This would have all the bending stress of stem flex on the thread which, having half the wall thickness cut away, will surely let go -- most likely when you're working the bar while climbing.

The relative diameter of the threaded area to the shank is important, because if the stem straddles the transition it'll clamp unevenly. This can be managed with shimming or body filler, but needs to be done well, so the stem clamps as intended. One way to check is to clamp the stem to a barely running fit on the thread and seeing if it can be worked down over the unthreaded area without being loosened.


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## aaronbarker (Aug 31, 2005)

FBinNY said:


> The critical issue is where the last thread is. If the thread ends well into the stem, and is not cut undersized compared to the unthreaded portion, you can go ahead and use it.


Regardless of whether this 'works' or not, I'd consider this bad advice and would caution against it.

have fun,
aaron


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## FBinNY (Jan 24, 2009)

aaronbarker said:


> Regardless of whether this 'works' or not, I'd consider this bad advice and would caution against it.
> 
> have fun,
> aaron


Would you care to clarify what your specific reason for considering it bad advice?

I thought I made clear the technical requirements for achieving 100% of the strength of an unthreaded steerer. 

Each of is entitiled to our own opinions, but for my part, I'd feel far safer with a threaded steel steerer that meets my conditions, than a carbon steerer with over an inch of spacers below the stem which is a very common arrangement.


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## iclypso (Jul 6, 2011)

If you'll forgive me the diversion, OP, why so averse to the threaded? I'm not looking to provoke an argument, I'm only asking for my own edification. A search of the forum failed to produce a reasonable discussion on the topic but I did find this thread to address the OP's original question:

http://forums.roadbikereview.com/bikes-frames-forks/can-threaded-fork-used-threadless-240277.html


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## FBinNY (Jan 24, 2009)

iclypso said:


> If you'll forgive me the diversion, OP, why so averse to the threaded? .....


I can't speak for the OP, but he might be in sort of a catch 22 situation. The same fork cannot be used with both threaded and threadless headsets. 

If the thread is in the area where a threaded headset would fit, that it would be below the stem of a threadless and cannot be used that way. 

OTOH if the fork is too long for a threaded headset, the OP has the option of extending the threads and cutting the fork, or possibly using it with a threadless headset if the unthreaded section is long enough to meet the conditions I posted earlier.

It's possible for a fork to be of an in between length and not usable either way, in which case the only option would be to extend the threads and use it with a threaded headset.


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## Scooper (Mar 4, 2007)

In THIS THREAD one poster suggests brazing a steel sleeve _inside_ the threaded part of the steerer tube to reinforce the threaded section. Since you're switching to a threadless stem, you wouldn't have to worry about the inside diameter of the steerer being able to accommodate a quill stem. 4130 tubing with 1mm thick walls extending an inch below the threads into the unthreaded area should easily provide the necessary reinforcement.

Again, you'd want to braze the threads and file the brazing material level with the thread crests.


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## RHankey (Sep 7, 2007)

IMHO, if one has sufficent skills and equipment to make and braze in a reinforcement tube, fill and turn down the threads so they don't cut into a threadless stem, then making a cusotm star or expansion nut, I think the time might be better served in brazing on a whole new steerer tube to the fork crown, as the fork is likely going to need a repaint anyway from all the heat that was required. For the time and effort, it would be cheaper and safer to simply buy or have a custom new threadless fork made, or use the original threaded fork as it was intended. I guess, to each his own. Just saying.


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## Kontact (Apr 1, 2011)

FBinNY said:


> The critical issue is where the last thread is. If the thread ends well into the stem, and is not cut undersized compared to the unthreaded portion, you can go ahead and use it.
> 
> What you absolutely cannot do is use a threaded steerer with any thread extending below the stem, or even close to it's bottom. This would have all the bending stress of stem flex on the thread which, having half the wall thickness cut away, will surely let go -- most likely when you're working the bar while climbing.
> 
> The relative diameter of the threaded area to the shank is important, because if the stem straddles the transition it'll clamp unevenly. This can be managed with shimming or body filler, but needs to be done well, so the stem clamps as intended. One way to check is to clamp the stem to a barely running fit on the thread and seeing if it can be worked down over the unthreaded area without being loosened.


This is wonky advice, and here is my very technical objection:

The stem derives its strength from how firmly it is clamped to the steerer. But if the upper stem bolt is attempting to pinch a threaded steel steerer with an aluminum stem body, the upper part of the stem is never truly going to be firmly clamped, so you end up riding on a stem with only the lower steerer bolt doing all the work. This is too likely to lead to a stem failure to make it worth doing.


On a broader scale, no threaded steerer tube is ever stressed this way. While the threaded section is normally inside and below the upper headset, the real stresses are transmitted from the bar to the stem quill, which is anchored below the threads.

Assuming that threaded steel is stronger than straight carbon is just that - an assumption. Cut threads are little different to the action of a pipe cutter.

The only way I'd ever consider doing this was if the threads were filled, then lathe turned for concentricity, and the inside of the steerer reinforced. Doing all that is more energy or expense than dropping $90 on a steel steerer carbon fork, or $50 on a steel threadless fork.

This is just a bad idea all around.


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## aaronbarker (Aug 31, 2005)

FBinNY said:


> Would you care to clarify what your specific reason for considering it bad advice?
> 
> I thought I made clear the technical requirements for achieving 100% of the strength of an unthreaded steerer.
> 
> Each of is entitiled to our own opinions, but for my part, I'd feel far safer with a threaded steel steerer that meets my conditions, than a carbon steerer with over an inch of spacers below the stem which is a very common arrangement.


Kontact addressed the technical issues with clamping over a threaded steerer very well before I had a chance to reply so I'd refer you back to his post. About the only thing I'd add is that it sets up a bad habit. Even if you clamp over the unthreaded part and ride successfully that way, you set up a false sense of security and might push the limits of that idea if you adjust the stem height up the threads a little more. You'll still have bending forces 'inside' the clamped area unless the threaded and unthreaded portions are somehow made identical diameters and concentric.

Also, you might mention at a group ride that you've successfully set up a threadless stem on your threaded fork in the manner that is suggested. One of the other riders might hear this and not pick up how the threads were avoided and clamp his directly over the thread. A ride or two later and it fails catastrophically on a ride. Not that you'd be responsible but I don't think anyone would want to be in that situation.

It's just as sensible and easy to convert to a threadless fork/headset or use a quill adapter and avoid all the potential problems.

I do agree with your aversion to over-spaced stems, makes me nervous, too.


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## Kontact (Apr 1, 2011)

aaronbarker said:


> I do agree with your aversion to over-spaced stems, makes me nervous, too.


I don't like to stack the spacers too high, but I'd like to hear a real reason for this being bad. The actual difference in leverage of adding a bunch of spacers is less than using a wider bar, so either it really isn't a big deal, or there's something about the spacers themselves that fail to secure the steerer properly.

Of course, Trek blames a rash of steerer failures on not having any spacers. Clearly this is a little bit of a complicated problem.


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## dougrocky123 (Apr 12, 2006)

*I converted*

I bought back a Ritchey that I sold to a doctor 15 years ago. It has a 1 inch threaded steerer and I wanted to update the stem and handlebar. I did what aaronbarker suggested and bought a 1" to 1 1/8" insert made by Profile. Worked like a charm!


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## foto (Feb 7, 2005)

You can clamp a threadless stem below where the threads start on a threaded fork (like a fork from a big frame going on a small frame). Otherwise, go with a quill stem, it looks better anyway.


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