ibbz":2sr0n8gx said:
I was wondering, with the majority of Retro bikes being either Steel or Ti, does Aluminium deteriorate over time? - even if not ridden 'hard' or thrashed?
Would it just crack or would the metal deteriorate naturally??
As Steel if cared for can to all intents and purposes, last almost forever.
As today most bikes, even budget ones are Alu, and they seem to be getting cheaper - it's either manufacturing costs are low (china?) or material costs are low - then surely the longevity suffers? Are todays bikes "throw away" bikes?
If you ignore all the fluff that gets wafted around any sort of materials question, a hardtail frame will usually fail at the heatube or the BB area, these are the areas under the most stress when a bike is ridden. Mountain/ all terrain bikes tend to be ridden harder so when they fail, its more obvious.
All materials can fail regardless of whats written on the internet. Ti has a nasty habit of cracking, steel of rusting and aluminium of simply failing.
The majority of frames just sit there, quietly, doing nothing for years at a time doing what they are designed to do without any issues, parts get replaced, the frame carries on.
Sometimes a material will get a bad reputation, Manitou made a frame that cracked, cracked some more and just to be really sure, it cracked again. This reputation spread around a bit and the mud stuck so even now, its still considered an iffy material despite science and physics saying otherwise. Various post build treatments change the properties of Aluminium making it a very lightweight and strong material. Fatigue only comes into play when a the material encounters a constant stress action (such as flying has on a planes wing) or a sudden mechanical action like hammering a headset cup - this can cause failures at a macroscopic level bursting out as a nasty headtube crack after a day or a decade of riding.
http://www.google.co.uk/search?q=headtu ... 66&bih=667
Titanium is the opposite, science and physics state that its a brittle material and not really suitable - many frames are an alloy of ti and other materials taking some of that brittleness away, unfortunately, they still crack and in odd places. The frame builders found on retrobike will tell you that its the joining processes that can do this damage as the heat changes the properties locally - the ends of the tubes being joined will end up with different properties to the rest of the tube. The same applies to aluminium.
The designers and builders take this into account when making a frame so most of the time, these frames will last for decades. This all fails when for instance, a Ti track frame gets used as a single speed commuter bike and the owner wonders why its cracked to buggery.
Steel is the wonder material and can be joined in many ways leaving the original material unharmed or stronger. The down side is that it is more prone to corrosion, often unseen, resulting in fairly spectacular failures.
I should have written this lot earlier, but I'd just got in from a 14 hour shift and was in need of a beer, or two, or three...
Going back to the earlier 'fluff', 6061-T6 aluminium seems to be able to withstand a 500,000,000 cycle stress test before it fails (if I read it right) - how that equates to everyday riding is difficult to say but loosely translated, its all hogwash and you should check for cracks in the obvious frames but most times, just go out for a bloody ride!
*Edited for bad spolling and spilt beer
