Of course, you can impossibly take spare parts with you, for everything that could possibly break. What I take with me, depends on where I will go. Today, bicycles can be found wherever people live. Most parts, such as tyres, tubes, cables... can be found in most towns, as long as you need nothing exotic.
Should you need something not available, parts can always be sent by post. This works quite well, as long as they know at home, what you need. For that reason, I always leave a list of spare parts at home, just in case.
Usually I have the following spare parts with me:
My cycle tours
