Originally Posted by
Choke
I would think that even the older chainrings would have no problem with newer, narrower chains. All chains from 5sp to 11sp are the same width on the inside (3/32", 2.38mm) and only the outside distance changes. I use a 9sp chain on all my vintage bikes and they have worked fine over a variety of different parts. The only possible place that I could see a problem would be if the chain was narrower than the chainring spacing and would get caught in between, but that hasn't happened with the older cranks that I use....Campy, Zeus and TA.
Now that you point it out, you are right I think. Internal dimensions haven't changed. Should not on principle be a problem to use modern chains on new 'narrow' chainrings. I measured my 10/11 speed modern Sugino chainrings and they are 1.92 mm. I've got some old TA rings in my stash somewhere. I'll pull them out when I have time, but I assume they'll also be in the ballpark of 2.0mm.
FWIW I did have some trouble with a modern 7 speed chain getting stuck between chainrings on my vintage Stronglight 93 cranks. Not stuck as in jammed in, but every once in a while it would not quite make the shift and kind of ride in between. So modern chainrings with their pins etc and modern chains have obviously evolved together.
AFAIK and FWIW, an actual 5/6 speed width chain is no longer made by anyone. Modern 5/6/7/8 speed chains are the same width as the old Suntour 'Ultra' and Sedisport chains. Once upon a time those were considered narrow. From memory I think that width is 7.1mm. The old full width bushed chains were more like 7.4 I think, but I don't think I have one around to measure.