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PostPosted: Mon Jul 22, 2013 5:45 pm 
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Did you do a lot of 1,7+Kw sprints during your commutes then? Under normal, easy riding, circumstances I'd reckon any decent quality aluminum frame would do 45.000km with ease... I mean, a lot of people do that in 4 years worth of regular training...

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PostPosted: Wed Jul 24, 2013 6:55 pm 
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boolinwall wrote:
Nope. You're not losing your mind. Aluminum lacks memory. Meaning that it doesn't snap back into place the same way steel or titanium do. It also doesn't deflect the same way the other two metals do. This is what gives aluminum it's stiffness advantage over damn near every other material out there. It will, however, soften over time. Mind you, for most people who aren't a protour sprinter, we're talking years and years. It'll also depend on the quality of alloy and heat treating. Better quality alloy and heat treating = better memory.


What?

Memory, for real? WTF?

Aluminium is not a stiff material, whatever that means. It is a light material and can be reasonably manipulated into shapes.

No again, aluminium, more appropriately alu alloy, will harden over time due to work. Harden as in brittle. Not soften.
When you see problems with alloy frames, it's usually to do with the welds due to the process at junctions. The material won't just fail out of nowhere.

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Posted: Wed Jul 24, 2013 6:55 pm 


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PostPosted: Sat Jul 27, 2013 9:09 pm 
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Aluminium, as a metal has a finite fatigue life, earlier alloy frames like vitus/alan used same diameter as steel frames but used thicker tubing to try and off set the fatigue that would be caused by flex, when companies like cannondale realised that by oversizing aluminium tubing they could reduce flex and therefore reduce fatigue while also reducing the weight aluminium frames became more popular. So basically an aluminium frame has a finite life, stiffer frames will have a longer life because they flex less and therefore reach that finite life time way later than a flexable aluminium frame. How long is that life time? Who knows.


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PostPosted: Sun Jul 28, 2013 1:51 am 
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^^^
Aluminum will fatigue at areas of repeated stress and oscillatory locations -- typically junctions. But won't just fail anywhere.

Earlier manufactures of alloy frame simply adopted industry issue tubes and joined them together. Only later we had butted and oversized tubing and then hydroformed tubes because the cost to manufacture came down and there was a consumer market for it.
It's difficult to generalize a stiff frame being less susceptible to fatigue. Oversizing a tube won't make it more stiff per se. It will make the tube more stable though and also depending on amount of material used either increase or lower its weight.

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PostPosted: Sun Jul 28, 2013 8:24 pm 
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My first Felt F1 frame was aluminum. I blew out the bottom bracket on that frame within about a year.


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PostPosted: Sun Jul 28, 2013 11:42 pm 
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The "frames get soft" stuff was the word around the bike shop in the early 80s, but was said about steel. I always figured it was just meant to sell more bikes.


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PostPosted: Sun Aug 04, 2013 9:38 pm 
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bah... . 45.000 kms? sure over 100.000 kms
I live in Vzla 3rd world. So not all guy ride new carbon bikes. I know a fellow who rode-raced-crashed an alu bike for around 15 years before the AL fork cracked, and the he rode the cracked fork unnoticed for I dont know how long. 2-3 hours 5 times a week. so thats 350 klms a week for 15 years. I'm lazy to do the math, yes he is lightwieht 60- 62 kilos.
My S1 2006 has over 60.000 klms still use it , beater bike, bad weather, some training in city red zones. I weight 62-63 kilos. have crashed too.
I know some guy with and old gios he might be around 80 kgs ex pro sprinter. that frame is around 10 years still uses it.
I could keep listing alloy frames.


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PostPosted: Mon Aug 05, 2013 12:06 am 
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Hi,

kbbpll wrote:
The "frames get soft" stuff was the word around the bike shop in the early 80s, but was said about steel. I always figured it was just meant to sell more bikes.


I'd like to see figures on frames getting soft over the years too. My educated guess is that this is one of these cases where if you can't build in obsolescence, you can still build a myth about it...

For the record: I own a second hand Bianchi Alloy SL frame made around the year 2000 which was raced with by the original owner. So, that one's pretty old by today's standard but I'm still riding it. Heck, it may very well survive me...

Same goes for that steel Bianchi I have as well. Ignore the brand names, it really doesn't matter.

Ciao, ;)

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Last edited by fdegrove on Mon Aug 05, 2013 11:54 am, edited 1 time in total.

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PostPosted: Mon Aug 05, 2013 1:25 am 
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Actually there is no myth... EN testing is routinely done on carbon and alu frames. On carbon we have to mainly worry about the impact test, as it passes fatigue tests with extreme ease, while for thin walled alu the biggest issue is fatigue. These are hard cold numbers at work (no marketing gimmicks, no fancy acronyms), just fasten the frame and put 1100n of force on the pedals and repeat 100,000 cycles (EN 14781).

Fatigue by definition means tiny cracks forming in the structure, so while getting "soft" may be one of the results, collapse or "breaking" is the bigger issue here.

Now what does that mean for the average consumer? The answer depends on what you are riding and how you ride it. A 85kg powerful rider on a thin walled 1100g frame or a 65kg spinning nerdy type commuting on a 1500g frame? Notice the EN test uses around 115kg of force, which means you are simulating a 115kg rider pretty much out of the saddle the entire time. In practice a 65kg rider spinning while seated is much less taxing on the frame. At this type of load, an alu frame will last a reasonably long time.

That being said, alu is indeed the most prone to fatigue compared to ti, carbon and steel.

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PostPosted: Mon Dec 16, 2013 2:09 pm 
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I have both a 20 year old vitus and a 16 year old Klein ...don't use the vitus on the road and the Klein is now my so called winter or backup bike now I have a litespeed archon T1 ... I'm sure the Ali frames will out last me if looked after and still enjoy their looks ,but don't know about how well they last with performance fatigue and sure the titanium will last for alot longer :-)


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