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I was wondering why for a relatively long time the most common fork set-up was the threaded + quill stem one. Why?

  • To me, it makes sense to try to have one point of failure for the the steering system of a bike (handlebar and fork), but it does not seem appropriate that said point of failure is hidden, requiring the disassembling of parts of the bike to be checked for its conditions.
  • From the fork manufacturing point of view, threaded and threadless fork still share the design of the 2 tubes down and 1 tube coming up, with the possible failure at the connection between the two parts, so I see no reason for making the top part "shorter" and then having a stem reaching down into it to connect.

This question states that threaded stem are stronger, but the "test"[a] does not convince to me as being reliable.

I reserve myself to put here the answer, if I find something useful in the next weeks/months.

[a] holding the front wheel between your feet and checking if you can turn the handlebar without turning the fork ...

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It depends what you mean by "a relatively long time". You're looking to compare one against the other, but that is only possible now they both exist. The threadless headset was patented in 1990. So for the 100 years of safety bicycles before that point, there was no comparison to make.

Once it had been invented, it was quickly adopted by the world's bicycle manufacturers. It may not be superior in every way, but things rarely are.

For a timescale on the changeover period, I give you the 1999 Specialized Allez, which adopted a threadless stem over the previous year's threaded. I regard Specialized as relatively responsive to cycling trends and it took about 9 years to see this innovation arrive on one of their mainstream, base model, road bikes. Threadless headsets are now effectively ubiquitous on all kinds of bicycle.

In the grand scheme of things, ten years or so for this system to become widely adopted isn't such a long time.

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  • I think the question is about why it took 100 years to invent a better headset, not why it become common in 10 years. By the way, 1 inch threadless headset + fork are drop in replacement for frames designed for threaded headset. – ojs May 20 at 9:10
  • yes, that's why I mention "relatively" ... 200 years from now stackexchange will be around, as well as some threaded fork :) My question was on why it took so long to develop from the threaded to threadless, and why the first design was the threaded instead of the threadless (which is evidently superior on many aspects, although not all). – EarlGrey May 20 at 9:23
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The threaded design is good enough. Sure it is heavier than necessary, flexy, has the single point of failure, the stem can seize in head tube, it is more expensive to manufacture and requires special wrenches to adjust, but none of these problems is exactly a showstopper. On the other hand, it has the benefit that the height can be easily adjusted until the stem is stuck.

For a long time there was no strong incentive to invent a different system, but when threadless headsets were invented, they quickly took over the market.

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  • but why it was created in first place? Especially the " it is more expensive to manufacture" it is puzzling me in making it the preferred choice. – EarlGrey May 19 at 20:15
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    Even if threaded headset and stem are more expensive to manufacture, they are still pretty cheap. And back in the old days when different frame sizes didn't really exist and bikes were often shared between many people, the adjustability was more important than now. – ojs May 19 at 20:42
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    It's interesting how innovation happens. Someone develops something new, it looks so intuitively obvious you wonder why it wasn't thought off long ago. – P. Barney May 20 at 2:18
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In a word - tradition.

A bike looks like a bike because that's what bikes look like. Quill stems and threaded headsets endured for so long as the normal will be at least partly because of this.

I was going to say that manufacturing requirements contribute, but the argument doesn't stack up for forks where the steerer length is either trimmed at install, or hidden by the top cap.

In short, Cycling suffers from a boat-anchor of "that's the way we always did it" compounded by UCI regulations mandating what bikes look like.

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    Could you point out when exactly did UCI ban threadless headsets? – ojs May 19 at 20:40
  • I think the past tense is needed refering to cycling suffering 'boat anchor' effect - UCI might be that way, but the MTB industry no longer hesitates to throw out last years standards for marginally better ones this year. – mattnz May 19 at 21:12
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    @ojs I never said that. I said that the UCI mandates what a (race) bike looks like. And that tends to dictate what bike makers offer. My point was tradition makes things last in cycling for a long time, and it takes a disruption before things change, and when they do the effect is sudden (okay over a decade or so, which is quite quick for the bike industry.) – Criggie May 20 at 3:10
  • If you didn't, I don't understand how UCI is relevant to the question. Besides, threadless headsets were originally invented for mountain bikes, which UCI initially did not want at all. It does not look like they were very successful at stopping them. – ojs May 20 at 6:34

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