Bicycle frame materials – explained - article comments

BikeGremlin

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To prevent article pages from being miles long, but preserve all the useful questions and answers provided over time, I've decided to copy/paste the website comments to the forum - and "move" further discussions here.

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Bicycle frame materials – explained
 
  1. Ralph J Pearce
    19/02/2022 at 23:38
    I’m not sure when this was posted, but to my mind as an amateur cyclist, a curious and, generally informed person, it’s spot on. I only wish that the author would speculate a bit on what material is best for whom. For example, is a carbon fiber the best choice for an overweight person who is seeking fitness. Or is titanium, that expensive for people who want an enduring bike. That kind of stuff.
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      Relja
      20/02/2022 at 07:59
      Hi Ralph,
      Different people have different budgets, tastes and preferences. So it’s difficult to make any broad recommendations.
      Also, regardless of the material used, some frames are stronger than others. A lot (most of it) is down to design and manufacturing (and quality control).
      What I think would make sense is to recommend a bike for the very heavy people. I get that question often, I’ve built such bikes, but still haven’t written an article on it.
      Edit: built as in picked components and assembled (including spokes, hubs, rims and wheel building)- I don’t make bicycle frames.
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    Nic
    18/08/2022 at 16:37
    Would you agree that tensile strength mostly and ductility but to a much lesser degree are the material properties that determine whether a metal tube gets “easily dented” or not? Besides those material properties it is of course wall thickness that is another major factor. If the above is correct then a titanium tube is a less dent prone than a steel tube of the same wall thickness because titanium has a higher tensile strength (and higher ductility).
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      Relja Novović
      18/08/2022 at 17:46
      Hi Nic,
      I’ll first make a disclaimer that I’m not a mechanical engineer, so take this with a grain (or a bucket 🙂 ) of salt.
      Let’s first define the basics.
      – Ultimate tensile strenght = maximum load a material can take before breaking.
      – Yield strength = maximum load (or stress) a material can take before being plastically deformed (bent, dented, i.e. won’t spring back into the original shape).
      – For very brittle materials (i.e. not very ductile), ultimate tensile, and yield strenght are basically the same – they will shatter rather than become plastically deformed.
      – For very ductile materials, yield strenght is much lower than their ultimate tensile strength.
      Now, since we’re talking about dents (plastic deformation), I suppose that yield strenght is what we should primarily be concerned with. I.e. we don’t care when it will completely break (the ultimate tensile strength), we just wish to see which one resists being dented (plastically deformed).
      With that in mind (if any of my assumptions are wrong, I hope a good mechanical engineer will correct me 🙂 ):
      All else being equal (wall thickness, diameter, impact object’s shape, hardness, kinetic energy etc.), I would say that yield strenght is primarily what makes a difference. The stronger, the less likely it is to get a dent.
      Ductility does play a part, but to a lesser degree I’d say.
      To make it a bit more complicated:
      Past a certain point, ductility will primarily make a difference in terms of whether we see a dent, or a material shattering/breaking. Of course, if we’re comparing some extreme ductility values, the material might just surprisingly easily get a dent if too ductile, or shatter if too brittle (depending on its hardness, and yield strenght, as well as the impact force, shape, direction etc.).
      Another important aspect to consider is the type of impact. Kinetic energy, hardness, shape, size etc. As well as what we are trying to achieve. But if we’re talking about bicycle frames – neither to ductile, nor too brittle is good. Just as a minimum of yield strenght is also required. Without that, it’s no use, no matter how light a material is. At least that’s my opinon and as far as I know. To be more precise – we need stiffness and ductility (but not extremely ductile of course), and the ultimate tensile strength is usually a good indicator of those (except for the composite materials, which have their own peculiarities, as explained in chapter 7).
      I hope I’ve explained more than I’ve confused. 🙂
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    Nic
    18/08/2022 at 16:52
    * I think it should be yield strength (not tensile strength). But I guess those two are pretty well correlated anyway.
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    Eduard
    19/08/2022 at 13:09
    I wonder if at the final notes in the aluminium section :
    “For us that cycle in the winter: salty sluch abundant on winter roads will eat aluminium, unless it’s protected with a coat of paint.”
    Didn’t you want to refer to steel instead?
    Thanks for all the information you provided, much appreciated!
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      Relja Novović
      19/08/2022 at 13:27
      Hi Eduard,
      Thank you for taking the time to ask this reasonable question. I’ll make sure to update the article to make it more clear, and will explain it here too:
      Aluminium will generally not rust in the rain and similar – not like steel does, not all the way through. It will form just a surface layer of oxide, protecting it and preventing any further oxidation.
      However, when we’re dealing with salty water, it will eat through the oxide and continue doing damage.
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    mike
    07/07/2023 at 11:53
    Hi Relja,after riding old retro chromemoly bikes i dont think i will ever change to a bicycle made from anything else,you can build up a very respectable bike from an old retro frame using modern parts,no they are not the lightest bike but they are very nice to ride and they are pretty much trouble free and these old bikes will run forever,i did a few searches just to see who in australia was still hand building lugged cromemoly bikes,to my suprise there are still a handfull of guys handmaking bikes,they will also do any repairs on retro bikes and even re-paint some for you,labour is the big cost but its well worth it if you need a custom lugged frame bike,years ago just about every bike shop had a frame builder and wheel builder at the back of the shop,the choice of bikes was endless,the 1980s saw many big changes in bike building and components as there were so many folk building bikes,you did see alot of innovation and new ideas,i still think the best bikes were built in the early to late 1980s,columbus tubing,tange tubing,reynolds tubing just to name a few,there is one builder who is making an exact copy of a columbus tubing bike from 1982,with those fancy italian lugs and italian components to go with it,i think its a craft that needs to be kept alive as once its gone its gone forever,cheers,ps i think i am saving up for that lugged columbus tubing bike,its a nice one.
 
Henrik Manoochehri
17/07/2023 at 23:30
If you’re not competitive riding, then high quality steel is the best choice. End of controversy! It’s the least fatiguing and most able to deal with shock of any kind/resilient. If you do a double century on all the different frames, it will become clear.
 
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