As I already started with some questions on flat mount I figured I might as well do a complete build log.
Jump in at anytime to comment or suggest alternatives.
Plan: Build a new bike for myself. It should include:
Electronic Shifting (Didn’t need it so far. Don’t know if I’ll like it but also here I want to find out)
Disc brakes (still don’t know if I am a fan on pure road bikes - but will find out
Geometry similar to my existing road bike(s)
So fortune or not. I manged to buy a slightly used Ritchey Carbon fork for 150€ which marks the start of the project and also defines a lot on how the frame has to look like.
Topic 1: Headtube
Fork has a straight 1 1/8” steerer and an molded lower bearing race.
I though to go for a classic 36mm headtube with an EC34 headset as it’s the lightest and aerodynamic (haha) solution.
Downside: The looks and I am limited it the diameter of the downtube to make it look good.
Only alternatives: EC37 - would look better I think but limited headset availability and I would need to buy yet another reamer.
Or an IS42 headset/headtube but also for this I’d need to buy a new reamer.
For the head tube I would use the 36.4mm OD one from Reynolds which also has the advantage that you don’t need to ream at all. They’re supplied with 34mm ID. Was interested to learn from reading the Paterek manual the other day that he also mentions this lack of a need to ream Reynolds headtubes so it’s not a new innovation!
If you use 36mm that only gives you 1mm wall thickness which I think might be a bit sketchy for welding or fillet brazing. I assumed those were intended for use with lugs. But I could well be wrong.
I’m not convinced that you don’t need to ream those bigger headtubes. I don’t think it’s good advice. I don’t doubt that you could press a cup in, but that aluminium cup isn’t going to be round when it goes in. And that’s not going to be great for long-term bearing life.
Yeah, I’m sure they press in. My point is that I doubt the cups are round once they are in. And reaming won’t make the fit looser than the tool is designed for (unless the walls are very thin and the cutter is blunt).
If it’s slightly oval then the reamer will remove material on the narrow bits and then the cup might be a bit loose once it goes in because it will only be being gripped on the parts you reamed that were too narrow. The other bits will be too wide. That’s why for an EC34 headset they say you want an average diameter of 34mm. However, if it’s very oval, it will squash the cups too much as you say. If your joining process tends to ovalize the tube that much it’s better to use a thicker one with an ID that is slightly undersized. Then when you ream it will be perfectly round and the right size. Really that is the perfectionist’s solution anyway I agree. But I’ve always found the Reynolds HTs to be fine on my TIG frames.
I can report that deda 44id head tubes are made the same way. It is a cool thing when you don’t have a reamer, but i prefer columbus that’s slightly undersised, just because of the reasons you have mentioned above. With deda head tube the reamer enters freely and when spinning it vibrates. That makes me think that @stevenshand is right - the hole is already oversized, just not round.
it works in real life, but for some people might not be good enough.
The only problem someone mentioned to me once is that with the normal use of a bike the cup would rotate inside the head tube, they could tell because the position of the logo on a headset changed overtime.
Actually the plan is to go with some reinforcement rings on the headtube to make it a smoother transition to the headset. Looks like below. Distance between fork and headset could be a bit less but otherwise I think the transition looks quite good. Headset choice is a bit limited with the integrated crown race as I have to go for a headset with 45° bearing.
I also thought about the tapered headtube IS42/EC42. However, I don’t like the looks too much (would prefer IS42 straight then) and I would still need a reamer. And for the IS standard I guess its a must as you also have to do the 45° chamfer.
