I'm try to help out an aging cyclist with upgrades to help with knee issues. One difficulty is with climbing the gearing on the Fuji touring series IV isn't low enough. I thought that switching out the front triple from 50-48-28 to a modern hybrid or MTB crank might help and keep costs low. I found two options Sunlite triple 48-36-26 and a shimano M-361
with 42-32-22. I know that the BB will have to be changed out. Is there any compatibility issues that I need to worry about if I'm running this with 6-speed cassette? Also the bike currently runs a 172.5 would a shorter crank be helpful for knee issues?