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TLDR: Can I wedge an EC30 into what seems to be EC29 (29.8mm)

I'm in possession of a mid-90's frame with a:

  • Head Tube Inner diameter of 29.8mm (Which seems to class as EC29)
  • Threadless Steering Column at 1" (25.4mm)

Its my understanding that this makes it a threadless EC29/25.4, which to my surprise is NOT sold virtually anywhere. EC30/25.4 on the other hand is easy to find

Am wondering -hoping- that the difference between the two is so negligible that manufacturers discontinued EC29 with the idea that people simply buy EC30

thoughts?

-b

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    Note for old timers like me: EC29 is the same as JIS. It has always been uncommon. In addition to matching head tube and steerer tube diameters, the headset also has to match the crown race on the fork, and that one is different between JIS and ISO too. – ojs Oct 14 '20 at 11:42
  • roger that, thanks for the heads-up! – Boro Ortega Oct 14 '20 at 11:46
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    When you are considering press fit tolerances 0.2mm is massive. If you tried to press in an 0.2mm oversized cup you’d run the risk of splitting the head tube. – Argenti Apparatus Oct 14 '20 at 11:51
  • yeah, thats what I was afraid of... so EC29 and thats that... thanks! – Boro Ortega Oct 14 '20 at 12:05
  • Machining EC29 head tube to fit EC30 headset probably wouldn't be difficult, but you'd still have to somehow match the crown race. – ojs Oct 14 '20 at 12:34
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It's unclear how it came to be a JIS (EC29) frame with threadless. That combination is odd. There are some different ways it might have been hacked together, or maybe some small number of bikes were made that way. It doesn't matter. Get the frame reamed to ISO/Campy/EC30 (all names for the same thing) and the crown milled if needed, and then you can install an obtainable new 1" threadless headset on it.

Some manufacturers of basic OEM and repair type headsets use the same cup profile for everything. Taking advantage of that is one way you could in theory combine two headsets to make a good hack solution. But it would be way easier to just machine the frame.

Jamming an EC30 headset in should not be done under any circumstances. The frame will be at risk for cracking now or later.

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  • Awesome tip, thanks Nathan. To be honest as soon as I picked up the frame (from the Austrian equivalent of Craigslit) I suspected something seemed off between the fork and the frame itself. Now I'm putting 2-2 together. Regardless, I'm also thinking that machining it is probably the solution with the least amount of headaches. thanks again – Boro Ortega Oct 14 '20 at 19:58

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