Originally Posted by
cny-bikeman
Count the teeth on the front chainwheels and rear cogs, Google bicycle gear chart, and plug in the tooth counts. Then encourage your wife to ride the front/rear combo that is closest in gear ratio to the small/small. As noted that combination will wear the drive train faster than any other, and it's actually quite a high gear ratio.
Small/small is 42/15. She's only recently gotten comfortable shifting with downtube shifters. I shudder to think what might happen if I tell her she'll need to "adjust the left side too".