The official spec for my new frame (2024 Orbea Laufey) are IS42/30 and IS52/40 according to the Orbea website.
My other frame (Revel Rascal) is IS42 IS52 and doesn't specify the second number for either top or bottom.
I had therefore bought this which is apparently 42/28.6 and has worked well so far.
| Color | Black |
| Crown Race | 40 |
| Bearing Type | Cartridge |
| Defined Color | Black |
| S.H.I.S Upper | IS42 |
| S.H.I.S Lower | IS52 |
| S.H.I.S. Stem Clamp Diameter | 28.6 Threadless |
| Lower Stack Height | 1 |
| Upper Stack Height | 9 |
Can I buy the same headset for the Orbea and ignore the difference between 28.6 and 30 (I have no idea what it refers to, is it of any relevance?)
Thanks a lot!
The second number is the steerer diameter at that point. So bearing ID. 28.6 is 1 1/8.
Standard for a tapered steerer is 28.6 top, 40 bottom. (Actually 39.8 but usually referred to as 40)
I haven't seen 30 for the top before, hat's not even the annoying 1 1/4; standard. Because that would mean you'd have a different diameter stem as well? In suspect a 28.6 would be fine likely due to the conical compression washer.
@submarined That article you linked for me in my fork thread is very helpful
Yup, will do, that's standard tapered steerer size. This might help understand(and the example given is the same as your dimensions)
Thank you but still totally confused. I appreciate that the top of the fork steerer tube is 28.6 BUT IS42/30 (as opposed to IS42/28.6) is a thing and on their blue paper I don't think Orbea have made a mistake. I'll try and put a IS42/28.6 and see what happens. l just thought I had finally understood headsets...
IS42/30 is a lower headset for a 1 1/8 straight steerer, the 30mm is where the steerer flares from 28.6mm where the crown race seats above the crown. It would come with a 30mm ID crown race rather than a 28.6mm ID compression ring.
Its not uncommon for manufacturers published specs to be wrong.
IS42/30 is a lower headset for a 1 1/8 straight steerer, the 30mm is where the steerer flares from 28.6mm where the crown race seats above the crown. It would come with a 30mm ID crown race rather than a 28.6mm ID compression ring.
Its not uncommon for manufacturers published specs to be wrong.
This. Some headset manufacturers quote it as "Lower IS42/30" and "Top IS42/28.6"