[bike] found something on craigslist, does it look like a good option?

[davester]

I've seen that article by Sheldon, and I usually trust Sheldon's judgment, but I'm not sure he's right in this situation because he omits a discussion of fatigue failure (this results due to loss of yield strength through cyclic loading). All the aluminum frames on road bikes I've tried have seemed harsh. It is possible to build an aluminum frame that has the resiience of steel and there are some good examples out there at the high end of the bike spectrum, but it is tricky because you can easily cross the fatigue limit where aluminum fails due to loss of yield strength over time. In contrast, steel is highly resistant to fatigue and it's fatigue limit is virtually never crossed under bike frame loads so it is easy to build a steel bike frame that never gets even close to its fatigue threshold. For this reason, most of the early aluminum frames were built ultrastiff, to provide insurance against failure due to metal fatigue. Even today there are a lot of aluminum frames that are overly stiff because it is tricky to build an aluminum frame that stays away from the fatigue threshold.