Todays subject on materials for bicycle frames is aluminum. It's probably one of the most widely used materials for frame building by mass manufacturers of bicycles. Step into your local "mart" store and check out the......ahem!, "bicycles" there or walk into most any independant bike shop and you will see a predominantly aluminum landscape. This wasn't always the case, and actually, it's quite a recent developement considering the history of the "safety" style of bicycle that we ride today.
Before I get any further into this, let's just clear up a few misconceptions out there. First, it's not just aluminum that's in that thar bicycle frame. It's an alloy of aluminum and other metals that make the combination something more than just plain, straight up aluminum. You may have seen or heard about certain four digit numbers that are bandied about by knaves and peasants in the bike shops or internet forums. Such numbers as 6061 T-6, 7000 series, or 2014 series. This one is that and such and such. You know...........poindexter stuff! It'd take a week of posts just to wade through it all, but if you've got the time, read this. I did, and it made alot of sense to me. Aluminum fabrication, welding, and processing is rather complex. It's easy to see why the bicycle industry didn't adopt the material for widespread use until recently. It's also readily apparent why the industry did adopt aluminum, as well. Read the paper in the link, and you'll understand more.
Now, let's get to the bicycle stuff! As I stated in my previous post, any frame material can be used poorly or brilliantly. Aluminum has become the meal ticket for most of your low end and entry level performance bicycle frames. These are the frames that are not anything to write home about, and in some cases, they may not get you home! Although that is, thankfully, becoming more and more rare. Suffice it to say that these frames are heavy, overbuilt, and display the worst traits in as far as riding quality is concerned. I'm not going to speak much on these types of frames, since they are not really indicative of what a good aluminum frame can be.
Getting to the good qualities that aluminum has to offer, we see light weight, stiffness, ( depending on the alloy used) and corrosion resistance, (again- dependant upon the alloy used). Usually, a highly manipulated, well thought out aluminum frame structure can rival the lightest of bike frames and ride rather well. Aluminum frame tubing can be butted, and formed into complex shapes. The typical rap on aluminum is that it rides too stiff, or in an unforgiving nature, that it's "dead" feeling, and that it "fails with out warning".
As with any "conventional wisdom" there are grains of truth and chaff of falsehood in each of the above statements. Let's take a look at each of the "raps against", shall we?
Rides too stiff: Well, again....not to sound like a broken record, but this is all dependant upon the specific alloy of aluminum chosen and the design that's used to build the frame. You can build an ungodly stiff, brutal machine, (Klein Attitude, circa 1992) or a really sweet handling, all day in the saddle kind of bike. (Cannondale Synapse in the aluminum flavor) You can even build an aluminum bike that is whippy and too compliant! Since aluminum can be tuned in several ways by shaping and butting, you can acheive most any desired ride qualities. Usually, folks that are talking this way, ( too stiff) are referring to the early 90's aluminum bicycles that rode like hay racks. To make this statement today about high end aluminum is just not fair or smart. Sometimes stiff is a good thing though, and aluminum is a great candidate for full suspension designs for this reason.
It rides "dead": Again, usually in referance to early examples of mass produced road bikes or mountain bikes in aluminum. Not necesarily the case today. One thing that has helped in this area is the use of front shocks on mountain bikes and carbon forks on road bikes. Road feel or trail feel is definitely different on aluminum, but not bad, and not extremely bad, as it was years ago. Does it ride like steel or titanium? No, but that doesn't mean it's worse......just different.
Aluminum "fails without warning": While aluminum can and does fail in a catastrophic manner, the instances of this occuring have been less and less over the years. Better understanding of the specific stresses imposed by bicycles on the design and construction of aluminum frame structures has helped manage the material better. As an example, do you remember when everybody was in an uproar over off road aluminum handle bars and how we should change them every three years? Well, while we probably should still do that, who really does? Have you heard that about handle bars recently? I remember when you couldn't open up a magazine without reading an article on that! It seems that aluminum technology for bicycles has come a long way since the early 90's.
This is not to say that aluminum is without it's faults, but usually that's dependant more on the design, how it's used, or misused, and other outside influences- not the material itself. Aluminum is generally regarded as a safe material, and it works quite well in the bicycle world. Is it for you? Possibly. If you are buying mass produced or small manufacturers bikes, you can't go wrong with aluminum. If it's a specific, custom design, it may prove a bit more problematic. While there are full on custom design aluminum bicycle frame builders out there, they are fewer in number than, say steel or titanium frame builders. So getting what you want might be a bit more of a hassle, but still do-able.
Finally, let me comment on a recent "fad" most commonly seen in road bikes, but also in off road machines. That being carbon fiber rear seat stays or complete rear triangles made out of the stuff and bonded to an aluminum front end. While I'm not ready to expound on the carbon fiber part of the equation, I just want to say that alot of designs utilizing this fashionable trend are nothing but, well........fashionable! It plays upon the consumers pre-conceptions that "aluminum is harsh- carbon fiber is good". Beware of poser designs! Nuff said!
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