Hi all! I'm working on a vintage build and am new to some of the compatibility issues for threaded headsets. I would like to buy a new Velo Orange headset and want to make sure I'm getting one that is compatible with the frame and fork. I believe the frame/fork is 1" JIS. Here are the specs I took for the fork and headtube:

Fork Crown diameter (where the crown race sits on the fork): 27.0mm
Head Tube inside top diameter: Approximately 29.9mm
Head Tub inside bottom diameter: Approximately 29.9.mm
TPI: 24

Here are the specs for the Velo Orange threaded 1" Alloy Caged Bearing Headset (JIS)

• Fork type: 1" English threaded
• Stack height: 41mm
• S.H.I.S. Upper: EC30 / 25.4-24tpi
• S.H.I.S. Lower: EC30 / 26
• Crown Race: JIS (27.0mm)
• Weight: 115g

Please let me know if you think this is compatible or not. Thanks for the help!

You need to determine how much stack your frame/fork combination provides. The VO headset needs 41mm of stack; if you measure less than that on your bike, you'll want to look elsewhere. You can use a shorter stack headset and make up the difference with spacers, but if the headset requires more stack than what you have, you're out of luck.

To measure stack, remove the headset cups and crown race from the frame and fork, insert the fork into the frame, all the way to the race seat, and measure the length of steer tube projecting beyond the top of the head tube:

Pretty sure that a 27.0mm fork crown diameter means it's JIS. If memory serves, those IDs for the upper and lower headtube ID are also consistent with a JIS headset.

However, as JohnDThompson noted, you also need to consider the stack height. The VO headset is nice, but it's relatively tall.

If the VO unit is too tall for your fork (e.g., if your fork doesn't have enough steerer length to support 41mm of stack height), Tange makes headsets with shorter stack heights - as short as just over 30mm (Tange Passage). Tange headsets also have a good reputation. Some of the Tange headsets are steel (the Passage is), some are cro-moly, and some are alloy.

FSA and others also still make 1" threaded headsets; ditto Dia Compe and some others. FSA components are generally excellent. The last time I needed one I needed an Italian threaded 1" headset for a vintage Columbus fork (I didn't want to use an alloy English threaded one and convert same permanently), so I ended up going with a Dia Compe - it was the only Italian threaded one I could find at the time.

Best of luck.

Thanks so much! JohnDThompson and Hondo6

Yes, the dimensions given for the VO unit are JIS. A JIS frame/fork can be milled to accept an ISO headset, if it comes to that.

Headsets with aluminum cups are taller than those with steel cups, as the aluminum parts need to be thicker than steel parts. Most Tange headsets are available in both JIS and ISO dimensions, and many decent steel models are available. Other companies may also have offerings in a variety of stack heights.

In my comment I was actually referring to the dimensions the OP gave for his headtube and fork crown ID. But yes, last time I checked VO does still appear to offer JIS, ISO, and French 1" threaded headsets (if they have them in stock).

Even for alloy, VO's unit seems to me to be a bit on the tall size. If I recall correctly, the other alloy headsets I have have roughly 3mm less stack height than VO's unit. One's a Shimano, and the other is the Dia Compe Italian threaded model I referenced earlier.

For an already-cut fork, 3mm difference can be critical. I was looking at the VO unit, but the fork I had acquired had already been cut fairly short and stack height might have been an issue. So I went with the slightly shorter Dia Compe unit instead.