If my derailleurs are for 9 or 10 speed (so narrower cage) and my cassette and chain (and shifters obviously) are 10 speed, can I get away with using an 8 speed crankset, or will that need to be changed out too?
Basically, I wanted to try out integrated brake/shift levers after only ever using thumbies, stem and downtube shifters, and the cheapest option looked to be a Shimergo setup marrying Campy 10 speed shifters (and potentially FD) with shimano (or compatible) everything else because the pull ratios were the same. So I got the derailleurs (Campy Comp Triple FD, Microshift Long Cage RD), shifters (10 speed Centaur), and an 8 speed triple cassette (lightly used RSX) and bottom bracket (Shimano UN-55 of appropriate spindle length). Then someone explained to me about a j-tek shiftmate that would allow 10 speed campy shifters to work with 10 speed shimano RD/cassette happily, so I thought I might try that instead of the shimergo setup because I could source the parts for an extra $50-60 and make use of all 9 clicks in my rear shifter instead of just 7, but only if I didn't have to replace the crankset (I'm tall and pretty strongly set on a triple and 175 road triples are expensive and rare-ish even used).
So basically, the question becomes whether to buy an 8 speed cassette and 8- (or 9-, I've heard that might work better with the 9/10 speed derailleurs)speed chain for maybe $40-50 or a shift mate, 10 speed cassette (tiagra is all I'd be able to afford or would need), and a 10-speed chain for more like $100 or so (with very careful shopping). If the 8 speed crankset and associated bottom bracket won't work with 10 speed, that makes the decision easy.