Considering an early '80's Miyata 610 for my wife. I have a mid'80's with barend shifters. She is not to keen on barends so here is my question. I am thinking of maybe 105's STI's but wonder if they will work with the older crankset?
Thanks!

How many gears will you run in the back? 9 or 10 speeds require more narrow chain and use more narrow spaced chainrings up front. Not for certain but I think the front brifter may work with both narrow or wider chain ring spacing.

If the bike is early 80's it would be friction shifted as SIS started in 86 ( 85 for Dura Ace ) and you would need to change out more then just the crankset. I know RSX had 7spd STI's but not sure on 105 as I have only had 8spd & up STI's in 105 & 600 tricolor. I had a problem running 8spd STI's with cranksets that had non SIS Front rings, I installed 9spd rings & everything worked perfect. You would need to change the Freewheel or cassette to SIS along with the chain, RD and install modern SIS shift cable & housing.


Glenn

You can use 8 speed STIs with vintage cranksets easily. More speeds than that and you'll have some additional problems to solve.

As mentioned, it depends on what generation of 105.
If you did 8 speed 105 or 600, the current crank could probably be fine. Ive used cranks which were originally on 6 and 7 speed bikes for 8 and 9 speed conversions without changing the chainrings. Shifts were/are fine.
If you want more recent 105, the chain will be thinner and may not play well with the thicker chain rings. You can always try before changing the rings. Ive read that the chain can 'skate' when shifting from large to small when using rings that are too thick for the chain.

New 105 may mean STIs, new cassette, new crank, new derailleurs, and new bottom bracket.

As an anecdote, I found 7800 Dura-Ace front derailleur/shifter and KMC 10sp chain to be compatible with 7400 crank, chainrings, and BB. The shifting was not 100% perfect, but maybe 90% there. After changing the inner chainring to a 10sp ring, it worked great. It did take some extended tinkering to eliminate chain rub inside the front derailleur in all ratios.

I had a 10sp cassette in the back as well, for people wondering.