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  1. #1
    Tim Krabbe - The Rider
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    Aluminium vs Steel

    I own a few bikes and am about to buy another to ride the streets of New York and to do some touring. At the moment I am in doubt about what kind of frame to get.

    I hear a lot of different stories about the power of aluminium frames vs steel ones. One side, including my father and grandfather, who both are blacksmiths, argue the (oversized) about 1 to 2 mm thick aluminium frames are not reliable enough for touring or riding the streets of New York daily. They both recommend oversized steel, I think because they've seen too much broken aluminium... On the other hand I my brother in law, who works at a bike store, says aluminium is strong enough, also if the aluminium frame is not at least 5 mm thick.

    My previous aluminium Giant Expedition alu 6061 frame was worn out after 6 years touring and riding the streets of Amsterdam. My iron Koga Miyata FM 2 commuter frame lasts already 15 years...
    Last edited by markus aurelius; 07-05-09 at 10:07 AM. Reason: typo

  2. #2
    Senior Member deraltekluge's Avatar
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    When comparing weight, strength, and durability of aluminum vs. steel, ask yourself how many steel airplanes you see flying around.

  3. #3
    Mrs. DataJunkie Luddite's Avatar
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    How many buildings are made of aluminum? (something my BF once said.)

  4. #4
    Tim Krabbe - The Rider
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    Because aluminium is cheaper then steel I assume. And for the parts that really need to be strong and I am sure Boing and others mix titanium with aluminium.
    Last edited by markus aurelius; 07-05-09 at 10:49 AM. Reason: typo

  5. #5
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    So far as I know no aluminum frame has 5mm wall thickness. Aluminum bike frames are typically made with oversize and relatively thin wall tubes for stiffness combined with low weight.

    Aluminum is subject to fatigue failure, more so than steel. Remember the commercial plane in Hawaii that lost the front upper cabin due to metal fatigue in the aluminum skin? Steel can also fatigue fail, particularly ultra light frames, but is less common. The culprit in most cases is repeated shocks to the frame such as chuck holes, curb jumping etc.

    An excellent discussion of frame materials and design is in the third edition of Bicycling Science published by MIT Press. Available from Amazon or orderable through your local book store.
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  6. #6
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    Quote Originally Posted by markus aurelius View Post
    Because aluminium is cheaper then steel I assume.
    Aluminum is much more expensive than steel.

    I think the proper answer would be that aluminum has a higher strength to weight ratio which is why it's used on planes but not in buildings (where weight doesn't matter and they could use the cheaper material).

  7. #7
    Quirky Grifter LesterOfPuppets's Avatar
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    Where I get raw tubing (not bike-specific), straight gauge 6061 T6 and 4130 cost about the same per foot, with thin wall steel being significantly more expensive.

    .049 wall 1.125 steel = $4.35, alu = $3.60
    .058 wall 1.125 steel = $2.95, alu = $3.10

    A straight-gauge alu bike would probably be nicer than straight-gauge steel, but nice butted steel is pretty sweet for rigid and front-suspension bikes.
    Last edited by LesterOfPuppets; 07-05-09 at 02:04 PM.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  8. #8
    Quirky Grifter LesterOfPuppets's Avatar
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    Quote Originally Posted by markus aurelius View Post
    I own a few bikes and am about to buy another to ride the streets of New York and to do some touring. At the moment I am in doubt about what kind of frame to get.

    I hear a lot of different stories about the power of aluminium frames vs steel ones.

    <snip.>

    My previous aluminium Giant Expedition alu 6061 frame was worn out after 6 years touring and riding the streets of Amsterdam. My iron Koga Miyata FM 2 commuter frame lasts already 15 years...
    How did the Giant frame "wear out" exactly?

    It sounds like you've answered your own question already and should be looking for a steel frame as we speak. One nice thing about aluminum is that it doesn't rust. Another is that a stiffer frame of lower weight can usually be made from aluminum. Which is good if you're a fan of stiff frames.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  9. #9
    Tim Krabbe - The Rider
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    Well, I do not have direct access to aluminium and steel prices but I have always understood that planes never use thin aluminium for parts that have to support a lot of weight. And don't companies like Boeing use nowadays a kind of multiplex aluminium? Aluminium with carbon fiber over it and in between a layer of very strong glue? But all I know is that for parts like the wheels they use massive materials and no tubes...

    I believe the first multiplex aluminium mountain bikes were made by Klein (with polyester or carbon, I can not remember exactly...) . I read that the guys who used these bikes drove them for a season and then threw them out... I believe that Principia used to use a similar technic in the early years too. These guys were scared that the aluminium underneath that glue polyester/ carbon layer was broken...

    And that is a little my worry with aluminium. That it could brake without letting me know. I am trying to find a frame that will last. Not one, like my Giant, that had several scratches and butts and which I indeed not trust anymore after 80 thousand kilometer. Little trips are or easy rides are fine but for to go fully packed downhill or driving it through a city full of potholes... Steel seems to be a little more forgiving. It will not brake at once. Maybe that is why they use it for buildings instead of aluminium. I do not intend to buy a new frame every few years...

    But as I have little and outdated knowledge of bike technology and I was hoping if anyone could point me at a strong aluminium frame or technology which will survive pot holes of New York City (this is no biking heaven like Amsterdam) and extensive trips. In the end it is lighter...

  10. #10
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    Quote Originally Posted by markus aurelius View Post
    Well, I do not have direct access to aluminium and steel prices but I have always understood that planes never use thin aluminium for parts that have to support a lot of weight. And don't companies like Boeing use nowadays a kind of multiplex aluminium? Aluminium with carbon fiber over it and in between a layer of very strong glue? But all I know is that for parts like the wheels they use massive materials and no tubes...

    I believe the first multiplex aluminium mountain bikes were made by Klein (with polyester or carbon, I can not remember exactly...) . I read that the guys who used these bikes drove them for a season and then threw them out... I believe that Principia used to use a similar technic in the early years too. These guys were scared that the aluminium underneath that glue polyester/ carbon layer was broken...

    And that is a little my worry with aluminium. That it could brake without letting me know. I am trying to find a frame that will last. Not one, like my Giant, that had several scratches and butts and which I indeed not trust anymore after 80 thousand kilometer. Little trips are or easy rides are fine but for to go fully packed downhill or driving it through a city full of potholes... Steel seems to be a little more forgiving. It will not brake at once. Maybe that is why they use it for buildings instead of aluminium. I do not intend to buy a new frame every few years...

    But as I have little and outdated knowledge of bike technology and I was hoping if anyone could point me at a strong aluminium frame or technology which will survive pot holes of New York City (this is no biking heaven like Amsterdam) and extensive trips. In the end it is lighter...
    There is one obvious thing I understand about your question. You do not understand the N+1 rule at all.

  11. #11
    Nighttime Rider
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    The word:
    Steel

    Think failure mode.
    Aluminum will usually crack before failure.
    Steel will usually bend before failure.
    (typically in a repeated stress location especially a bending/twisting force)

    Steel is easier to repair and has more give.
    Aluminum is stiffer.


    Also, the "aluminum is in airplanes" argument is invalid.

    What percentage of airplanes is CF?

    Doesn't hold up...

    Most big airplanes have a monocoque construction where the primary structure only gives stiffness while the skin of the structure takes a bulk of the stress.
    If you want to make a valid comparison, think of the Piper J-3 Cub. It is a steel tube structure covered with fabric.

    The "aluminum doesn't rust" argument is also invalid.
    Rust = corrosion = iron oxide
    aluminum also corrodes: aluminum oxide.

    I still don't get the "steel is real" slogan, but I do prefer it as a strong simple solution to my cycling needs.

    And that's the word....

  12. #12
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    Extremely long life is not a normal bicycle manufacturing criteria anymore so far as I can see, at least for the types of bikes available in the USA. Whether steel, aluminum or carbon fiber the criteria seems to be low weight and manufacturability at relatively low cost.

    Personally I would still trust a decent quality steel frame such as those from Surly, Salsa or others to outlast a similar quality aluminum frame if subjected to poor roads, heavy loads and lots of miles.
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  13. #13
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    CrimsonEclipse;

    Aluminum is NOT stiffer for the same diameter and gauge. In fact it is about 1/3 as stiff as same dimension steel as well as about 1/3 the weight. Current aluminum frames use oversize thin wall tubes to give the stiffness needed by the designer. A aluminum frame made with the same size tubes as used in a standard classic steel frame is way too flexible. It was tried in some early aluminum bikes with unacceptable results.
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  14. #14
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    I have had two steel bikes that failed. Neither one bent visibly before cracking. One gave plenty of warning since the crack was just of one seatstay so the only immediate effect was that the tire started rubbing against the frame. The other was less fortunate since the steerer tube gave way suddenly with the result that the front wheel and fork instantly separated from the bike. Luckily no serious injuries but 30 years later I still have some minor scars. Both bikes were repaired and are still in use.

    So far I have no personal experience with aluminum bike failures although the one I have now has had more miles than any of my steel bikes. It's almost 20 years old with over 170,000 km.
    Still not clear in what way your Giant aluminum frame wore out?
    Last edited by prathmann; 07-06-09 at 12:22 AM.

  15. #15
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    Your grandfather and father are right steel is much stronger and can take more of a load. Aluninum may be strong enough but not as strong as steel.

  16. #16
    Senior Member Retro Grouch's Avatar
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    These questions should probably be asked in "Politics and Religion".

    If you worship at the altar of weight-weeniedom, you have to buy a carbon fiber bike.
    If you are looking for a bike for all eternity, get a titanium framed bike.
    If you are Orthodox anything, steel's for you.
    If you are too cheap to put money into the collection plate, buy an aluminum framed bike.

  17. #17
    Senior Member dynodonn's Avatar
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    I prefer aluminum. I have two steel bikes, one is over 30 years old, rigid but very heavy, the other is newer/lightweight, but flexes considerably. My aluminum bikes have the best of both of my steel bikes, being lightweight and rigid, and they have plenty of miles of heavy loads racked up on them with no sign of frame fatigue.

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    Touring needs: A bent frame is easier to ride than a snapped frame. You're out in the middle of nowhere, which do you prefer? Touring involves carrying a load so frame weight is a moot point. Al has a tendency to flex under weight and stress. That leads to metal fatigue and failure.
    Whether you think you can, or think you can't, you're probably right

  19. #19
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Mr Danw View Post
    Touring needs: A bent frame is easier to ride than a snapped frame. You're out in the middle of nowhere, which do you prefer? Touring involves carrying a load so frame weight is a moot point. Al has a tendency to flex under weight and stress. That leads to metal fatigue and failure.
    Have you ever broken a frame? I have...four times! Two each of both materials under discussion. Aluminum when it fractures, in my experience, cracks and tears. It can take days or weeks for the crack to develop and the frame to be useless. Steel on the other hand...again, in my experience...does exactly what everyone expects aluminum to do. It fractures instantaneously. Both steel frames I broke when 'Ping! and were unusable. No warning of their imminent failure was ever given.

    I've also broken steel parts (a pedal shaft, many hub axles) and aluminum parts (a crankset and many rims). The steel parts, again, went Ping! and were broken. The aluminum parts groaned and complained for weeks before they finally failed.

    I've never understood this hatred of aluminum. Critical aluminum parts are all over a bike...handlebars, wheels, hubs, cranks, brakes, seatposts and stems...do those who worry about aluminum frames spontaneously combusting replace all those parts with steel ones? Probably not. Failure of any one of those parts is at least as hazardous as a frame failure and probably more detrimental to your health. But, since we don't want to ride 75 lb bikes, we ignore those issues
    Last edited by cyccommute; 07-06-09 at 11:14 AM.
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    Quirky Grifter LesterOfPuppets's Avatar
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    Recently, I personally debunked the "aluminum always fails catastrophically" myth. Taking my Mongoose with Nitto bars off a little one foot dirt jump. Promenades just aren't made for that. Sure glad they bent, as opposed to...you know.
    Last edited by LesterOfPuppets; 07-06-09 at 11:57 AM.
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  21. #21
    Humvee of bikes =Worksman Nightshade's Avatar
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    Please see my sig line for how I feel about aluminum framed bikes.
    My preferred bicycle brand is.......WORKSMAN CYCLES
    I dislike clipless pedals on any city bike since I feel they are unsafe.

    Originally Posted by krazygluon
    Steel: nearly a thousand years of metallurgical development
    Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?

  22. #22
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Nightshade View Post
    Please see my sig line for how I feel about aluminum framed bikes.
    So you ride an all steel bike? Really? With all steel components? Steel rims too? You are a braver man than I.
    Stuart Black
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  23. #23
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    I have had both Steel and Aluminum bikes. I like both and I plan on getting a CF bike next. But I am not into touring so my needs are different. I may even add a carbon fork to my Aluminum Road bike. They all have their advantages. Aluminum is lighter than steel for “the most part” so getting a lightweight bike in Aluminum is less expensive for the normally than steel. It also seems as if Aluminum is stiffer than steel and for climbing with a bike club flex seems to bleed off some power. Carbon Fiber is can be made light and can be designed to be stiff and light.

    There seems to be a rule in cycling that the lighter the parts the more they cost. But as far as steel lasting longer I don’t know how relevant that is. The frame might be steel and parts like the handlebars, fork and seat tube might be steel. If they are then you are pushing more weight than most Aluminum bikes sold by your LBS. You can make a steel bike lighter by upgrading the parts just mentioned but if you ever upgrade the parts on your bike the shifters, derailleur, cassette and new chain will still cost more than a steel frame. So the only solution I can see is more than one bike. But then that assumes this question is real and not just an attempt to get the Aluminum verses steel debate going all over again.

  24. #24
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    Quote Originally Posted by Nightshade View Post
    Please see my sig line for how I feel about aluminum framed bikes.
    That makes ABSOLUTELY no sense.

    We went THOUSAND of years without medication and cures, so should we stay away from the medicines that have only been around for the last 80 years???

    There are a thousand other comparisons that could be made using your line of reasoning, all of them fail.

  25. #25
    token triathlete Bah Humbug's Avatar
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    Quote Originally Posted by CrimsonEclipse View Post
    The "aluminum doesn't rust" argument is also invalid.
    Rust = corrosion = iron oxide
    aluminum also corrodes: aluminum oxide.
    The kicker is, iron oxide molecules are smaller than iron molecules, exposing fresh metal to the elements to rust. Aluminum oxide molecules are larger than aluminum molecules, protecting the good metal from damage.

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