Looking at building up a dedicated AL crit bike. I'll be going the ebay/craigslist route and hopefully getting a group and frameset separately.

Since I'm trying to keep costs as low as possible, most of the frames I'm looking at are used. Is there a good rule of thumb for age/mileage of an AL frame? For example, there's currently a Team Soloist I'm interested in with stated mileage of 'under 2500'. This seems reasonably low, but there are other frames out there with considerably more.

Just wondering where my cutoff should be. How long does a typical AL frame last? 10000 miles? 20,000?

Don't dent it, or scrape the paint up (leading to corrossion eventually) and a good aluminum frame should last you at least 100,000 miles.

Cervelo warrants those frames for life (to the original owner) and they were used in the TDF. It shouldn't matter if it has 10,000 miles on it, as long as it hasn't been abused and is in good shape.

Note from this study that a Cdale(admittedly an older model) was substantially more resistent to failure from fatigue cycling than a number of Steel and Ti frames. https://www.sheldonbrown.com/rinard/E...tigue_test.htm

Thus while an Al frame will eventually fail from fatigue, its not likely to be during the useful lifetime of the bike for most owners.

Don't set a cutoff, just avoid frames that look old or beat up. You can't tell when a crack is going to form, but if a frame looks pristine it's probably going to be good.

And used aluminum frames are fairly cheap, so you can afford to be choosy.

$99 Performance AL frame. https://www.performancebike.com/bikes...7_20000_400314