I have a mid-1980s road bike with downtube friction shifters. I'd like to install a freewheel with a larger cog (something like 32 or 34T), but my current rear derailleur won't accommodate that. So I'm looking into replacing my rear derailleur with one that has a greater max capacity.
I've been reading about derailleur pull ratios, and it sounds like if you install a new derailleur with a different pull ratio than the old one, then you also need to install new shifters. However, most of the comments I've seen have been related to index shifters, where compatibility seems to matter a bit more than it does for friction shifters.
Does derailleur pull ratio matter for friction shifters? Can I install a derailleur with any pull ratio and have it work with my current setup, or will I need to swap out other components as well (shifters, cables, chain, etc.)?
If pull ratio is important, how do I figure out the pull ratio for my current derailleur so I can find another one with the same ratio?