How to swap instances in a movie clip?

Hey everyone, hopefully this should be an easy answer. I haven’t had a lot of experience with actionscript other than setting up navigation for a website.

What my team is trying to do right now is build a game. It is a game where the user can build their own bike from different parts, and then test it in other challenges.

Right now I’m at the stage where they are building the bike. The first thing I’m trying to set up, is allow the user to push 3 different buttons that will change the appearance of the tires. I have the bike on a movie clip, then the tires on another movie clip within that, and then three different types of tire movie clips within that tires clip (make sense? bike>tires>3 tire clips). So I think the easiest thing would be is to somehow script each button on the root frame to just swap out the instance of the tire (the three types are: thick, aerodynamic, and trick).

I tried looking at the help and seeing if I could just have each one change visibility, but that wasn’t working out well for me. Thanks for your help ahead of time!