On Sun, Mar 7, 2010 at 6:25 PM, Mark Roberts <m...@robertstech.com> wrote: > frank theriault wrote: > >>You're right about aluminium's longevity (or lack of it). It >>literally starts micro-cracking the moment it's put together. 3 to 5 >>years is the longest I'd ride one (meaning that my Fondriest is >>getting very long-in-the-tooth). For a messenger frame, which tends >>to have a short lifespan anyway, it's not such an issue, but for the >>average cyclist, it is something to consider. > > FWIW, I think this is mostly urban legend, passed down through > cyclists, mechanics and (ahem) bike shop owners. Aluminum is used for > frames of racing motorcycles and aircraft and lasts a lot longer than > 5 years without trouble. Granted, it's likely to be different alloys, > etc, but the basic technology is the same. I know plenty of people > who've used aluminum-framed bikes for 10 years or more. > > A more cynical note: I can't believe aluminum-framed bikes would be > sold *at all* in the liability-lawsuit-crazed U.S. if half the stories > of their limited lifespans had much truth to them. >
Aircraft have limited stress lifetimes for exactly this reason. And a rebuild for a smaller aircraft pretty much comes down to stripping it and replacing the high-stress items at a certain set point in the lifespan. Aircraft also get inspected every 100 hours and if a pattern of stress cracks is found entire fleets will be grounded. Your motorcycle frame benefits from suspension which damps alot of the vibrations and stress (Aluminum FS bicycles also benefit from this by a large amount) and also benefits from the extra strength you can build in since compliance is provided by the suspension. FS bikes (and motorcycles) are massively overbuilt compared to the frames we are talking about here (a typical road bike frame made from aluminum is 3-4lbs) Aluminum frames don't have legal issues since the average user doesn't ride all that much and frame warranties tend to be quite good. Frame life is 5-10 years under heavy use, 10-20 years under light use, essentially forever under typical consumer use (most bike owners ride less than 100km per year). The real concern with Aluminum is if you are a heavy user (Racer, messenger, the hardcore MTB user running a rigid or hardtail) or if you buy an older frame which has been used in such a manner. -- M. Adam Maas http://www.mawz.ca Explorations of the City Around Us. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
