My trusty old Giant road bike (1990 vintage) is rapidly becoming my commuting bike. Its a great cromoly frame and very comfortable for me. Here's the thing: on my commute there are some hills...a very steep one on the way home. If it were not for them I'd be building a cool fixed gear/singlespeed with fenders. Right now the bike has a full Suntour Cyclone group (non indexed down tube shifters):
6 speed 12-24 in the back
52/42 chainrings up front
As the lowest cost option to get some lower gears, can I put a 39 up front and not have shifting problems? I want to avoid dumping too much $ into this right now. I want to avoid having to get a long cage in the back or buy a new crankset. Plus the small ring is slightly bent and worn anyway, so can a simply put a 39 there with no big impact? I know the ratio will not be significantly better but I only want a little bit.