When does fatigue set in?

Miguel asks Lance about his thoughts on aluminum frames.

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Miguel: I know aluminum is good. That’s not an issue. But I was reading the manual and it said that the frame should last at least two years. And yet they give a lifetime guarantee.

Lance: Probably just covering themselves from legal action. Maybe serious racers put more stress on the frames.

Miguel: But does lifetime guarantee cover accidents?

Lance: Not accidents. Faulty workmanship, yes. But if they see truck tire marks over a crushed frame they won’t give you a free new one.

Miguel: So then I asked about fatigue, metal fatigue, and there was some humming and hawing.

Lance: Yeah?

Miguel: And they said under fair use, fatigue wouldn’t set in for many years.

Lance: Avoiding the issue, eh? Anyway, the only way to check for fatigue is to cut up the frame, dye the metal and examine under a microscope. Best thing is, you should do a regular visual check on the fram, especially around the bottom bracket and the steering head.

Miguel: Steering head? I was talking about sunglass frames.

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