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Carbon and aluminum bike frames die from fatigue, eventually. And since they're weaker materials (carbon is very strong in some ways, very weak in others) they'

Carbon and aluminum bike frames die from fatigue, eventually. And since they're weaker materials (carbon is very strong in some ways, very weak in others) they're more liable to actually crack or bend irreversibly in a crash. Steel and titanium, to my knowledge, will never break from fatigue alone. You essentially need to hit them with a car or a hammer to break em. And you can always keep those frames going indefinitely with welded fixes, as long as you know a decent welder. Rust is what gets steel in the long term, if you don't keep your bike clean, especially if your town salts roads in the winter. But it's otherwise very robust. In the USA it seems like a lot of people just like new bikes, and neglect their old bikes. Some get stolen. Enthusiasts get upgradeitis. But compared to the carbon footprint of smartphones, cars, asphalt roads, factory farming, and a million other things, I'm not convinced it's a major issue.

ehnto 4y ago
In the west I think you are right, there's a bit of keeping up with the jonses going on. Lots of new specializations happening too, suddenly it's not good enough to have just a mountain bike, it has to fit the right specialization too. Downhill, enduro, trail, XC, gravel! I think we have finally ran out of sensibile suspension travel divisions to group bikes around, it might calm down now. I think the fatigue rate of an aluminum frame is overblown a bit. It is certainly a fact about aluminium, but does it actually occur over the lifetime and use of a typical frame? You can expect to use an AL frame for 10+ years, or tens of thousands of KMs, so it still has a longer shelf life than I think most cyclists have enthusiasm to ride. Consider that most AL frames are made of 2024 or 6061, the same stuff used on aircraft wings which have significant lifespans (30+ years). It depends on the grade and craftsmanship of course but I would not personally worry about the AL itself.
- wiredfool 4y ago
  I've had a Aluminum CX bike (kinesis built) have a fatigue failure in the bottom bracket cluster. That one also had the non-drive side crank have a fatigue crack at the BB interface. I've had a (cheap) Trek steel late 80's mountain bike have a fatigue failure at the chainstay bridge. Each one had thousands of miles, but not 10k. In each case, it was probably more of a welding or detailing issue than the actual material involved.

ehnto 4y ago

In the west I think you are right, there's a bit of keeping up with the jonses going on. Lots of new specializations happening too, suddenly it's not good enough to have just a mountain bike, it has to fit the right specialization too. Downhill, enduro, trail, XC, gravel! I think we have finally ran out of sensibile suspension travel divisions to group bikes around, it might calm down now. I think the fatigue rate of an aluminum frame is overblown a bit. It is certainly a fact about aluminium, but does it actually occur over the lifetime and use of a typical frame? You can expect to use an AL frame for 10+ years, or tens of thousands of KMs, so it still has a longer shelf life than I think most cyclists have enthusiasm to ride. Consider that most AL frames are made of 2024 or 6061, the same stuff used on aircraft wings which have significant lifespans (30+ years). It depends on the grade and craftsmanship of course but I would not personally worry about the AL itself.

wiredfool 4y ago
I've had a Aluminum CX bike (kinesis built) have a fatigue failure in the bottom bracket cluster. That one also had the non-drive side crank have a fatigue crack at the BB interface. I've had a (cheap) Trek steel late 80's mountain bike have a fatigue failure at the chainstay bridge. Each one had thousands of miles, but not 10k. In each case, it was probably more of a welding or detailing issue than the actual material involved.