Caveat: I haven't been to South America since the late 1990's. If you're going to be asking about parts availability in small towns throughout South America, also ask a few shop owners about tire availability. When I was down there 26" tires were almost universally available, 700c were only really available in the bigger cities. FWIW: 26" tires were the only thing I saw in Bolivia, and it was tough to find a 700C tire even in LaPaz (Santa Cruz Bolivia might be different, but I wasn't there long enough to get a good idea). Also ask about tubes, Presta valves weren't too common, Schraeder valves were. I wasn't bike touring down there, but still liked to look at what folks were riding for future reference. Nah, I ain't gonna go touring down there at this stage in life; those dreams have died away for me.