I have an 80's model Schwinn world road bike. It has a double crankset, not even a compact, just a double. I live in a very hilly area, and I really need the extra gears a triple will offer. I have stem shifters on the bike, so indexing is not a problem. I have an old walmart roadmaster mtb laying around, and I want to know if it would be possible to change the crankset from it to the Schwinn. I am only going to throw the Roadmaster away anyway, so would it be possible? I don't mind switching the bottom bracket too, I just don't know if it can be done.

This is going to be a temporary fix until I can afford a new, (or moderately new) road bike for myself, but since I already have the parts I thought I would give it a try.

The only trouble I see with this is that removing old cranks takes a special tool. Removing bottom brackets does too, but they can be coaxed off with a little ingenuity.

If this is an operation you are only going to do once, think about taking both bikes to a LBS and have them remove the pieces. Or, if it costs the same to buy the tool, as it does to have the LBS do it, then go ahead and get the tool.

The other tool you will need is the right sized socket to reach inside the crank arm and remove a bolt that is in there.

Sounds like a worthwhile swap, if it doesn't cost too much money.

I'm not terribly experienced with this, but you might run into trouble having enough range on your FD to accommodate not only the movement left to right, but also the designed capacity for differential between the number of teeth in the smallest ring to the largest. The current FD might not even accommodate a modern compact double.

Click around on the shimano products site and you'll see in the stats a number for "capacity" I think. I think that's the possible difference in number of teeth between smallest and largest ring.