Originally Posted by
garagetuner
Awesome. Thanks for the quick reply.
Just want to double check that when 35 - 26 = 9 it is still good to go (as it is less than the magic 16mm requirement)
A simple diagram of a head tube and steerer with dimensions labelled (A, B & C etc) plus a simple equation and requirements would be great.
For example,
Steerer Length (A) - Head Tube Length (B) = Excess Steerer Length (C), where (C) must be between 27mm and 45mm.
Excess Steerer Length (C) - Steerer Thread (D) = Excess Steerer Non Thread Length (E), where (E) must be less than 16mm.
I'll leave the diagram up to you 😀
Ha! I posted that having just woken up and clearly didn't proofread. The requirement is for the threads to end
no more than 16mm above the headtube so whether the correct math is 5 or 9mm, you are still good to go
What the <16mm above the headtube is ensuring is the upper race can screw down the steerer tube far enough to contact the upper bearing. The <45mm above the headtube ensures that the steerer tube doesn't bottom out internally inside of the quill/upper race portion. I could only accommodate a certain amount of steerer tube inside of that area before I start infringing on how short the unit could be trimmed for those wanting to run slammed stems with short-ish steerer clamp areas.
As
RobbieTunes alludes to, the measurements I selected also (not coincidentally) accommodate most frame/forks without any modification. It is only when a thick spacer has been installed with the original headset (for a touring bike or similar) that the steerer will be too long to work unmodified (see
Rocket-Sauce 's posts).
RobbieTunes I'm loving the Y-Foil with innicycle conversion. It just looks 'right'. Keep pushing that friend! I think I know what my next vintage build is going to be...