Problem with aluminium.

[Annoying Twit]

IME steel frames give a little bit of warning (e.g. by going floppy) before they break, but Alu frames and CF frames usually do not.

(Just out of curiosity) Does this include fancy steel alloys such as 731 etc?

[Brucey]

it does, but it also seems to depend on exactly where they break.

If the fracture occurs entirely within a certain part in the HAZ of some steels, the material that is breaking can be hard and brittle, so there isn't much in the way of floppiness to start with. However since the hard zone is usually narrow and the surrounding material is still (relatively) soft and ductile, at some point that material starts to yield and then the frame goes 'floppy'. If the failure is entirely within the softer and more ductile material, the frame/fork will go floppier earlier, all things being equal.

cheers

[Peter W]

Since relative agreement seems to have broken out, can I just add a bit about our teenage (13 to 15+) cycling style?

The country (early 50's) was in a dire near bankrupt state, with shortages and some food rationing (books and weekly coupons) still in force. especially for sweets!! Since there were no electronic gismo's, computers, or even television sets (first small grainy B & W sets just starting to appear) bikes were our obvious 'magic carpet' means of broadening our horizons, and didn't we 'arf make use of 'em!

Normal days out were from Darlington to Redcar and a blast along the beach to Saltburn. (Speedway style back wheel skids with foot out, from as fast as we could go.) If we occasionally felt like it we would 'do' Whitby and back (100 miler).

The odd thing was that, since we were not concerned with speed or performance, (push up the steep hills) we never really got very tired. We just rode all day, and only really got hungry and thirsty. (pocket money for fish and chips when there, but nowt left for all the way back. But we were told it was character building!

I sometimes look at touring cyclists on laden roadsters nowadays, and wonder who is really getting the most satisfaction out of cycling? At least they don't have to suffer hunger pains, or cycle in ordinary everyday clothes as we kids did. It's tempting to buy another steel roadster and join them, but then I look at the present 'hot shot' carbon bike and think nah! You can't slip into reverse and relive the past!

By the way, in the early 50's there was one roadster with a 50 year guarantee against frame breakage. Forget which.

[roubaixtuesday]

I was brought up 200 yards from that beach. Talking of blasting along the beach, did you know Donald Campbell broke the world speed record on the sands there?

Respect for cycling to Whitby from there, that's a tough ride.

[Peter W]

Yes, it's a superb low tide hard packed sand beach all the way from Teesmouth to Saltburn Mr. Fox. There used to be a single rocky outcrop where Redcar pier once stood, but it is mostly covered in sand now.

With regard to riding on to Whitby via the coast road hills, and back to Darlington via the Moors road (Jolly Sailors Bank and all that lot). We really didn't see it as being any great fete because, if you think about it, we were all riding our bikes day in day out, as a matter of course, so it was as natural as a person just walking (though faster and wider ranging) all day long. We were all young and fit, and just riding comfortably within ourselves. It just came naturally.

The other great point was the sparsity of road traffic at that time. Most of the main roads were still twisty and winding (before the widening, straightening of corners, and flattening of hills) and the majority of that sparser traffic was old beaten up pre-war cars, and chugging 20 m.p.h. (legal limit then ) lorries.

What I felt then, and still do, is that the human powered two wheeled bike has to be one of the happiest inventions ever. It is not the most exciting. On Sunday I watched the para gliders launching and soaring way up and out off the top of Carlton Bank (Yorkshire Moors) with one going for maximum height. (Looked to be around two to three thousand feet high, at a guess.) But I pedalled off (Mountain Bike) to follow along the cliff top track quite content in that my satisfaction in riding on two wheels was no less valid than their dare-devilry.

So best of luck to all riders and enthusiasts. Signing off, despite bursting with enthusiasm, and shutting up now!

[landsurfer]

OK ... so having read this post again is there there someone who will put their head above the parapet and say that,

" An aluminium bicycle frame produced of the correct grade alloy, for the duty cycle expected, will have an in use life of 20 years"

Or even 10 years.

My Decathlon frame is warranted failure free for 10 years ... based on what ?

Who applied the warranty .. Decathlon Engineering Dept .. or ... god help us ... Marketing ... !!!

I have a steel SPA framed bicycle which i call my "Lifebike" ... it will out live me.

I want my Decathlon alloy frame to be the same.

[barrym]

Well, I'll start off saying that I'm not an expert on anything. However my current bike is a Trek 7100 aluminium alloy frame and is 9 years old and done a lot of miles. It is 9 years old and I'd expect the same again. My previous bike was an aluminium framed GT and was getting on for 15 when I got rid of it, and was as good as the day I bought it as far as I could see.

So, whilst I lust after something steel, I can't say that aluminium had ever let me down.

[reohn2]

When researching buying our Cannondale tandem,as Cannondales were built in the US at that time(now built in Taiwan), I asked on a couple of US tandem forums for advice on them and particularly on lifespan and frame failures.
There were a few who claimed they'd owned there's for over ten years and rode them regularly with one chap who openly admitted he and his wife/stoker were a bit on the lardy side (can't remember the details but they we're a hefty pair)who'd owned there's for 20 years,rode it regularly and never had a problem.The general consensus on those forums was that they were a sound bike/make and not to worry.

Given this was a tandem,subject to far more stress than a solo,and not a heavy bike either,ours was sub 20kg with mudguards and a rack,which we owned for almost ten years(it was a 2005 road model,which we bought s/hand in about 2008/9 IIRC)without any issues and sold to a forum member's friend about a year ago,which AFAIA is still being used regularly,I'd say aluminium frames are capable of a long lifespan

[Si]

" An aluminium bicycle frame produced of the correct grade alloy, for the duty cycle expected, will have an in use life of 20 years"

I have two Zakar frames (LE & Team Issue) which are 22 and 18 years old respectively...they've been crashed numerous times, still going strong, apart from paint damage. Never met anyone who has broken one...most get retired because they don't have the capacity to take modern longer travel forks. On the other hand, I've had Alu frames from other manufacturers which have, in the worst case, lasted only two weeks.

[amediasatex]

I have two Zakar frames (LE & Team Issue) ..... Never met anyone who has broken one

Waves...

Does 'meeting on the internet' count? 1997 Zaskar, headtube parted company with rest of frame some time in 1999, but I wouldn't take that as evidence of much a you'll see from my history few manufacturers or materials have a clean record under my care!

" An aluminium bicycle frame produced of the correct grade alloy, for the duty cycle expected, will have an in use life of 20 years"

I doubt anyone will come out and say it directly for all the reasons already posted over the last few pages, evidently many Alu frames do last that long, even some of mine!

My Decathlon frame is warranted failure free for 10 years ... based on what ?

Warranted for X years only ever means they've run the numbers and expect to get few enough failures that the cost of replacing the ones that do break is minimal/absorbable, and that's true for any material and any value of X, even so-called 'lifetime' frame guarantees. I doesn't mean they promise it wont break, it means they promise that if it does break due to a defect in either design, build or material that they'll give you a new one for free. That's all, no more, no less.

Many warranties are an exercise in marketing and making you feel like the product is of good quality, rather than any indicator of longevity in the long run. Even a company that offers a lifetime warranty, the extra sales from the reputation and feel-good factor alone might offset the cost of absorbing issues, it's all a numbers game in the end...

[Vorpal]

OK ... so having read this post again is there there someone who will put their head above the parapet and say that,

" An aluminium bicycle frame produced of the correct grade alloy, for the duty cycle expected, will have an in use life of 20 years"

An aluminum frame can certainly be designed to achieve that. Lacking any quality and construction issues, many will.

No one here will likely stick their heads over the proverbial parapet because we simply don't know what the design life, designed duty cycle, and factor of safety are. I can make some educated guesses. But I wouldn't make a statement about the life of an aluminium bike frame on that basis.

I have a couple of bikes with aluminium frames, and I'm perfectly happy to ride them, and furthermore, I am confident that I will never break them because I expect that they are designed for 60th or 70th percentile usage, and my usage is more like 30th percentile. Mini V also has an aluminium bike frame, and I am quite confident that she will never break hers, either. It's possible that someone else will.

[Peter W]

Sorry to burst out again, but surely a concern must be that some recent aluminium framed road bikes (not talking about far more robust alloy M.T.B. bikes with full shock absorbing suspension) are on a roll with claims of being lighter and just as strong ( a clear marketing contradiction) owing to clever design and construction, even when using the material for added compliance (bending) for comfort. (Were all previous alloy designs unintelligently constructed?)

Everybody knows the old saying about lighter, stronger, cheaper, but taking just the first two, lighter and stronger (or even lighter and JUST as strong as before) has proven to be false in other fields, especially the marine one. It's not easy to imagine that many of these latest lighter alloy road bikes will prove to be very durable, even for average non powerful riders. Bumpy roads and pot hole poundings work the same for all.

[Vorpal]

Sorry to burst out again, but surely a concern must be that some recent aluminium framed road bikes (not talking about far more robust alloy M.T.B. bikes with full shock absorbing suspension) are on a roll with claims of being lighter and just as strong ( a clear marketing contradiction) owing to clever design and construction, even when using the material for added compliance (bending) for comfort. (Were all previous alloy designs unintelligently constructed?)

It's true, for a certain value of 'strong'

More seriously, it depends how you define strong. if you take the same size and thickness tube in aluminium alloy and steel, the aluminium one will weigh about 30 or 40% what the steel one does, and be half as strong. If, on the other hand, you take an aluminium tube and a steel tube that have the same ultimate strength, the aluminium will be lighter. It's possible to select an aluminium alloy tube that has a higher ultimate strength and lower weight.

The main thing that puts some people off of aluminium is that it does not have a fatigue (endurance) limit. A steel structure that never sees a stress which exceeeds the fatigue limit, and which is protected form damage, corrosion etc. will never break. Of course most steel corrodes eventually.

Aluminium has much better resistance to corrosion, but it will eventually break due to fatigue. If it is well-designed, that shouldn't be within the life of the structure (in our case bicycle frames).

The graph on Wikipedia illustrates the point pretty well....

What we don't know is where that line is for any given bicycle. With steel, we can generally trust that normal usage will not exceed the fatigue limit, so it doesn't matter where the line is relative to one's usage. With aluminium, it very much matters, and can make the difference between a bike lasting 2 years, or the rest of one's life.

There are many other things that make a significant difference to the life of a frame: build quality, alloyed materials, build methods, protection from corrosion, etc.

Build methods and build quality are the biggest causes of failures experienced by cyclists. Few put enough miles on a bike to see end of life failures, and the majority of bikes end up in a tip or recycled before they reach their functional life capability. I'm not trying to suggest that cyclists never experience end of life types of failures. The folks who frequent a forum like this are rather more likely than most to have done so.

[Samuel D]

It's not easy to imagine that many of these latest lighter alloy road bikes will prove to be very durable, even for average non powerful riders. Bumpy roads and pot hole poundings work the same for all.

However, if you look in other places on the web (e.g. Reddit’s cycling subs), it is apparent that large numbers of cyclists including outright novices spend huge sums of money on bicycles, mainly by replacing them at a fantastic rate. Since most of these people aren’t doing big miles, it follows that each bicycle has a very short life indeed in their possession. What happens to it when it’s resold is the new owner’s problem as long as they don’t sue the manufacturer for harm caused by bad design or manufacturing, something that happens rarely because of the high cost and low chance of success against the good lawyers employed by American bicycle companies like Specialized.

It would be rational for the manufacturers to respond to this new reality by reducing the durability in favour of other, more marketable features like lower weight. Cheap methods of hydroforming aluminium alloy have allowed new designs in pursuit of that goal.

[Brucey]

one thing that isn't obvious to most folk is that the stresses that matter (fatigue-wise) are the highest ones anywhere in the structure, in relation to the material's local capacity to resist such stresses; these will be the ones that initiate a fatigue crack first.

One of the biggest culprits is a thing known as 'geometric stress concentration'. For example drilling a round hole in a tube (even if you do it carefully) will cause the local stresses to be increased by a factor of three or more. Unfortunately weld beads in bike frames always have much worse stress concentrations than that; x10 or more. The worst concentrations are hidden from view (weld back beads in most aluminium frames look pretty disgusting in fact) and only the fillet geometry spares most such welds from starting to crack the first time the frame is used. Any defect on the outside of the weld, eg at the weld toe, can cause a crack in time.

The other thing that is usually grossly underestimated is the effect of corrosion. This has the effect of weakening the material so that the service stresses that will initiate and propagate a fatigue crack are substantially lower. Aluminium is only corrosion resistant by virtue of a tenacious oxide layer and by and large that oxide layer is less coherent and tenacious the stronger the material is; the alloying elements usually create second phase particles and these cause the oxide film to be imperfect. The other things that make the material less corrosion resistant are

- breaches in any other surface coating (including paint or anodising)
- the presence of a crevice
- the presence of a second (different) metal/material
- the presence of a corrosive electrolyte (eg water contaminated with road salt)
- thermal cycles that affect the structure of the material internally.

The last of these includes (obviously) welding. Thus a welded aluminium frame can have local regions that are both mechanically weakened and are lacking in corrosion resistance vs the parent alloy. Spray with salty water and the parts may have a small fraction of their original fatigue strength.

If you live somewhere dry and/or don't ride in the rain then you don't need to worry that much about corrosion; the parts may fatigue eventually, but that is a bit random anyway. However if you live and ride anywhere where they use road salt, your aluminium bike and its parts may well have a greatly reduced service life if the possibility of corrosion is not addressed.

Note that through most of the 'lightweight era' it has been possible to weld (rather than braze or otherwise bond) bicycle frame tubes together, in both aluminium and steel. For some of this time such processes have been expensive to implement but the main reason they were not used for decades is that it is difficult to make a frame that is really fatigue resistant. TIG welded steel frames don't last for ever either, but that counts double or more for aluminium ones and more again for any welded aluminium frame that has pretensions of 'compliance'.

cheers