What I'm doing is explaining the key interfaces between components, and then giving you a database to look up appropriate parts.

For example, if you regularly use your bike in the rain, you can easily find out how much it's going to cost you to replace your drive train components each year. I know numerous regular commuters who have spent more than $600 a year to keep their commuter bike in good shape. Yet by selecting a bike with a more basic drive train, the cost can be reduced to less than $150. There are $12 chains and there are $50 chains. There are $25 cassettes and there are $150 cassettes.

This website will let you figure out what it's going to cost. And how easy it will be to get parts.

This website has two things:
 1. Explanation of the main interfaces
 2. Databases of available parts

Here are some things you could do:

 - compare the key specs for a number of standard bikes
 - look up how much it will cost to replace the drive train
 - figure out what parts could be used on your current bike
  For example, if you were looking at a given bike, you might want to quickly investigate the availability of replacement chains, wheels, stems, cranksets.

The idea is to figure out how easy it will be to get parts for a given model of bike.

This website explains the important interfaces between the main components on a standard bike. For example, what are the standard dimensions you need to know to buy a replacement wheel.

if you need a new rear wheel, you can list all the wheels available, and filter the list to the ones that will fit your bike.

In order that you know what to specify, there is a master document which describes the standard measurements for each item. For example, to buy a wheel you need to know the dropout width, rim diameter, and brake type. If you already know these things, you can directly search and see what is available.

These days there are some really great videos on Youtube that explain how the different parts fit together. So I link to these videos in explaining each of the key interfaces.

  Wheel to frame Interface
  Brake mount type
  Stem to frame Interface
  Seatpost
  Cassette replacement
  Chain types