I have a an older (mid '70s?) Cinelli handlebar that I am unsure of the clamp diameter. My guess would be that it is 26.4, but I have measured it differently.
With a set of digital calipers, the reinforced portion of the bar is 26.13mm on the non-knurled part (outside of where the stem clamps) and is 26.20mm on the knurled section where the stem clamps.
Does anybody know if these numbers match up with the 26.4 mm Cinelli standard? Or is theree some 26.2 mm standard that I haven't heard about?
It just seems odd to me because I measured a 26.0 mm bar at 26.00 mm.
Middle 70's will still have the ornate crest(s) depending on the model, one may be different. there was a minor change after the 1R stem was introduced to make that stem work better, so the first thing is to verify the date. Cinelli outline typography with the winged C is very late 70's at the earliest. The bars with the star are 80's and are the most likely to be the 26.0 type.
The thing is that it doesn't fit a Cinelli 26.0 mm X/A stem. There was an X/1 stem on it, but I took it off, and now the binder bolt just spins. I think that the X/1 worked like a seat binder bolt that bites in on one side, only the side it bites in on doesn't have an allen wrench fitting.
I'll probably just end up filling the 26.0 until it fits.
26.2 for a used bar is not unheard of...depends on how it was installed, and how many times it was installed. The outside diameter of the bar should be a little less than 26.4, I think, to get it into the stem (especially a problem with the 1R stems.)