Which bicycle frame material is the best?

Posted by on Apr 30, 2009 in Bicycle Parts, Blog | 13 comments

This is a question that has been tossed back and forth since, well, since the first bicycle was made. Each material used (aluminum, steel, titanium, or carbon) have their advantages and disadvantages whether they be weight, cost, or strength. Most riders, though, seem to prefer one over the other.

In the last 10 years or so carbon fiber frames have gained in popularity beginning with carbon fiber forks being placed on bicycles frames made from metal. Now you can get complete frames made from carbon fiber including additional bicycle parts like seat posts, brake levers, wheel sets, handlebars, cranks, and water bottle cages. The only limitation you have is the size of your wallet.

For those that can’t make the move to a full carbon frame, many manufacturers produce bicycles that use a mix of both carbon fiber and aluminum materials. Typically these are aluminum frames with carbon fiber forks, seat stays and/or chain stays. These types of configurations keep the costs down while letting riders enjoy the benefits or carbon – weight savings, ride dampening, and poseur-ness.

The poseur-ness factor is only fully enjoyed if you also ride in a full team kit and shave your legs. Is there anything wrong with the poseur factor? Heck no. I hope to be able to achieve that level someday. Just not sure about shaving my legs though. We’ll have to see.

The question, as the post title so aptly states, is which bicycle frame material is the best? I expect a lot of different answers here (assuming folks take the time to answer) so don’t hold back. Tell me which is the best and why you think so.

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  • http://www.wirewd.com/bike/ Wirehead

    So, you do need to remember that a while back, they made 6 bikes out of totally different steel alloys. They all looked identical and were painted identically. And even though the biking mags in those days talked about the benefits of one alloy over the other, nobody could actually tell a difference.

    Much illusion. Few facts.

    It's clear that if you want to go fastest, carbon fiber is the way to go. It is the present winner in the competition to make the lightest weight bike that doesn't snap when you sit on it. If you are racing, even if it's a fraction of a mph, it may be a huge difference.

    I don't trust that a bike company is going to have enough money after paying the marketing department and sponsoring riders to actually hire a good engineer for things.

    This is why I don't quite like carbon fiber. It's got a totally different set of design properties than any metals and it's fairly unforgiving when you don't design it right.

    My personal fetish is Titanium. It's got enough of the positive working properties of steel, but it's lighter weight. Only downside is that the welds are tricky to do right. Must use plenty of shielding gas and carefully clean the parts. Also, if you can make bikes, you can also make titanium aircraft parts, so you have to pay welders a lot.

    I tend to think that part-carbon-fiber bikes are a really stupid move. There's a long design problem history that suggests that if you do carbon fiber, you should do all carbon fiber. Making the seat stays and/or chain stays carbon fiber just means that you've got a great spot for a crack to form. Forks make a little more sense, given that you've got the bearings and stuff there.

    On the other hand, titanium bikes are going to always be a specialty expensive item. So I'm left with aluminum by default. Sure, aluminum will stress-fracture at some point down the road, but at least it won't suddenly unravel. And it is lighter than steel.

    The problem, of course, is that I want a well-constructed durable aluminum frame, not a cop-out design for somebody who isn't ready to upgrade to carbon fiber.

    Maybe one day I'll just teach myself titanium welding and make my own frame…..

    • http://bikingtolive.com Bryan

      Uh, wow. Great detailed response.

      I worked with titanium back in my submarine days and am aware of the welding issues. I tend to agree with you on the part-carbon fiber bikes. Makes sense that where the carbon and metal join may be a potential weak spot with them being dissimilar materials. You'd think they would have tested stuff like that wouldn't you?

      • http://www.wirewd.com/bike/ Wirehead

        I don't think the problem is so much gross flaws. After all, you can only compromise the bike so far before it'll just fall apart when you sit on it, no?

        It's more along the lines of spending more money on a Al + CF frame that just cracks at the join in five years than you would on a full Al frame that doesn't crack after five years.

        And since I personally think that most of the differences in tubing are imaginary and the benefits of losing a smidgen of weight are also imaginary, replacing part of the frame with a carbon fiber bit just doesn't make sense to me.

        As far as the stress fracture thing, it's kind of like the rust on your steel bike, Al. You can make a spring out of steel and it'll never break because steel can flex and then un-flex up to a certain point without suffering wear. On the other hand, if you make a spring out of aluminum, it'll eventually break because aluminum wears when you flex and un-flex it.

        Thus, the design point of aluminum is to design a bike such that the estimated life-span will be exceeded before it's accumulated enough metal fatigue for cracks to form.

        This is a fairly understood thing, largely because aircraft are mostly aluminum and so they've applied a lot of engineering analysis to it such that metal fatigue usually requires something else to go wrong.

        Really, I don't trust bike makers to get this right either. I just figure that aluminum failures tend to be more gradual and less catastrophic than a carbon fiber failure.

  • http://mildstallion.wordpress.com Al

    I made an observation about the high-end frame manufacturer, Serotta (I live 20 minutes from their factory). They make frames in Carbon, Ti, and Steel only. They have some mixed frames, but the fact that they eschew Aluminum always made me curious.

    Wirehead insiuated stress fractures as an inevitability – is that true? My bike is steel and after 17 years, shows no signs of rust – but that's the second thing steel haters complain about (the first is weight). I wonder if the stress fracture issue is backed up by real numbers.

    I say this hoping it isn't true, because my next bike will most likely be an Aluminum frame & carbon fork.

    • http://bikingtolive.com Bryan

      First, let me state that I'm not a bike frame engineer so I have no idea if my experience holds any weight.

      When I worked on nuclear reactors I had to take several classes in, and deal with, stress limits, stress fractures, and cyclic (no pun intended) stresses. The things I worked with dealt with metals and stresses caused from high temps, high pressures, and heating/cooling. Like I said, I'm not an expert, but I would think that any bicycle frame material would be susceptible to some type of cyclic stress problems due to the constant frame flexing that occurs. Particularly with heavier riders like myself.

      I would think that bicycle frame manufacturers could pre-load the frames to reduce these cyclic stresses.

      • http://www.wirewd.com/bike/ Wirehead

        Hrm, so my understanding… and I’m not a bike frame engineer either… is that some materials (Titanium and Steel when the correct alloy is used) have a fatigue limit, so you can flex them a certain amount indefinately without metal fatigue. Thus, as long as you don’t go over that limit, it’ll last quite well.

        The problem with preloading the frame or otherwise overdesigning frames that have no fatigue limit (like Aluminum) it is that you end up with a frame that’s no lighter than a frame made of an inexpensive material that doesn’t require preloading. And, honestly, given all of the R&D that the car companies spent making their steel car bodies not rust that can be applied to a steel bike frame, you can’t really trumpet the rust-free thing either.

        I also am a strong believer in material as a source of personal identity. Maybe I just feel like a non-ferrous dude? :D

        • http://MildStallion.wordpress.com Al

          I dunno, Man of Steel sounds better than Man of Aluminum!

          • http://bikingtolive.com Bryan

            If you were Man of Aluminum you wouldn’t have a magnetic personality either.

          • http://MildStallion.wordpress.com Al

            I’m gonna go ahead and pretend I didn’t hear that.

            • http://bikingtolive.com Bryan

              You gotta admit it was kinda funny. :-)

  • nikromatt

    For me steel is the only option. A bike made out of any other material is like the American Baseball League. It's a form of baseball, but its not real baseball. I'm also not a recreational, group, or club rider or racer. So weight is a factor. I'm all about bikes as utilitarian transportation. This is just my person opinion and not meant to put down anyone else's personal choice in frames material.

    • nikromatt

      Should read: Weight is NOT a factor.

    • http://bikingtolive.com Bryan

      First off, thanks for stopping by and leaving a comment.

      I think you bring up a good point that the purpose the rider is using the bicycle for will have a heavy influence on their view of frame materials.

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