I'll soon start a rather long trip from Ushuaia to Alaska. As I'm from Europe (France), I don't really know what to expect about spare parts for my bike in south America.
I'll ride a Kona Rove ST, a gravel bike with 650b wheels and 47mm wide tubeless tires. The train is 1x11 SRAM. How easy do you think it will be to get new tires or to replace gear parts?
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generally speaking you probably won't find spare parts for your bike. Only exceptions would be, maybe, Santiago de Chile, Lima and Colombia main cities.
On your bike set up.... 1x11, if you have the standard 32 tooth in front change it for a 28. A bit more range when loaded never hurts (still hope you are going bike packing not fully loaded).
And same thing for tubeless, not strictly best option especially if fully loaded... Get a pair of Marathon as wide as you can fit and tubes. That's 10000 km free of worries.
Remember if you have problems most of the mechanics you'll find along the road will not have the proper tools to fix your bike (eg a cassette removal tool compatible with SRAM cassette).
Study some spanish before leaving, research on Casa de ciclistas, firefighters (bomberos) hospitality and you will have the best time of your life, even when cycling against Patagonian winds (you will since you cycle north).
Chile actually has a well-developed network of bicycle shops across the country, Oxford. If one shop doesn’t have the part you need, they will order it from another shop and it will arrive in just a few days.