The following mechanical summaries is from an 18-month/27000km trip from Prudhoe Bay to Ushuaia in 2016/2017:Reflections:

• Disc brakes: I have become a big fan of disc brakes – mainly because of a failure I didn’t have. As a rider who is both heavier than average and cautious, I wear through brakes. On previous trips, this also eventually meant a failure on the rear rim. This didn’t happen on my trip. I replaced rotors once and brake pads many times, but didn’t have any rim failures.
• Hubs/Wheels: I had two hub failures, both with a Phil Woods hub and the pawls sticking down and the hub spinning freely in both directions. After that, I had Sugar Wheel Works build up a different wheel around a DT Swiss 540 tandem hub. I took an extra ratchet mechanism and grease with me, but the hubs worked without a problem. In my experience, while Phil Woods makes a strong hub, it seems like also important to get the mechanism opened, serviced and cleaned and that is difficult for me to do on the road. After four Phil Woods failures, two prior to this trip and two on this trip, I am more shy about using them on other trips. Through the failures, I was pleased with service I had from Sugar Wheelworks.
• Frame: The right chainstay of my aluminum Trek 4500 bicycle was cracked in Bariloche and welded. There is sometimes a debate about the suitability of Aluminum vs. Steel on touring bikes. Despite the failure, I am still undecided on the debate.
• Derailleur: My rear derailleur twisted off the bike in the mud of the Dalton Highway. For now, I still think of this as a fluke that happened once in many cycling miles.
• Tires: I used three different models of tires during the trip: Schwalbe Marathon Plus, Schwalbe Marathon Mondial, and Schwalbe Marathon Supreme. The first two are heavier but also extremely durable tires that served me well. The Supreme tires are considerably lighter (and hence faster). They held up well enough, though I did eventually have enough punctures that I ended up picking new tires back from the USA. Once I got past Mexico, I didn’t see Schwalbe tires in bike shops I passed along the way. They might be there if one searches more.
• Tubes and tire sizes: Through Latin America, I had 26″ wheels but with Presta tubes and not the more common Schraeder valve. There is also a debate in cycling community about 26″ vs. 700C in Latin America. I carried enough spare tubes and in my experience, the odd sizes I had were not an issue.

Notes from a long supported ride across Africa in 2013 include the following:
- two flat tires during the entire trip; other riders had up to 30, Africa is full of thorns. I had two marathon+, one marathon dureme and one marathon mondial
- brought extra brake/shifter cables. Didn't use but other riders did have cable issues after sandstorm in Sudan
- replaced my middle chainring along the way (it wasn't new at the start)
- used three sets of spare brake pads
- replaced a cassette and chain 2/3 of the way along the trip
- used a replacement derailleur hanger in Ethiopia