Bikes are put together in a bunch of different ways with a bunch of different materials. A quick, (ok not quick, it turned out to be really long) run down looks like this:
Aluminum. Most bikes sold in the US are aluminum. Sometime in the early 90’s, aluminum became cheaper by the foot than steel. At the same time, robot welding was getting really good, and fat aluminum tubes took kindly to robot welding. Aluminum typically is TIG welded, a welding process that involves super heating the tubes together with an electric current. There’s a gas involved, but for the sake of simplicity, think of the tubes getting so hot via this electrical current that they melt together. That’s what’s happening at a basic level. Aluminum TIG welds are big and fat, and good ones look like a stack of dimes spread across a joint. TIGs themselves are light weight, and because you are just melting two tubes together, you can put the tubes together at any angle, which is a good thing. Good TIG welds are very strong, the idea being the weld will be stronger than the surrounding tubing, and the tubing should fail before the weld. You know someone or something messed up when you see a cracked weld.
Aluminum has to be oversized to get any stiffness out of it. If an aluminum bike had steel bike sized tubing, it would ride like a wet noodle, and indeed, early aluminum bikes did and do ride like day old Soba noodles. TIG welding is really hard on tubing, because the tubes are melted together. Melting isn’t a gentle process, unless you are melting butter in a cast iron pan and not thinking about it on a chemical level. Melting involves immense heat and that heat can distort tubing. This is important to note with all TIG welded materials, Steel and Ti included. Because of this heat, tubing needs be thicker at the ends of the tube, where the weld happens. This thicker tube resists distortion but affects ride quality and tube weight. Thicker tubes are stiffer and heavier.
Aluminum has a finite fatigue life, and parts that are hanging out on a shelf, getting lightly banged up, are aging just like parts on your bike do. Interesting, anodizing, which was designed to protect and strengthen aluminum, speeds corrosion when the anodizing is scratched. A raw aluminum part will last longer than anodized or painted part, but no one makes raw aluminum bike parts any more. They did in the 70’s though. Most aluminum bikes are on borrowed time after a decade. Same too with handlebars, rims, anything extruded. Stems and cranks tend to last way longer, if they were designed well.
Aluminum does not suffer dents well, and, like Titanium or Carbon, is compromised and generally just waiting to break after it’s dented. Steel can be dented as long as the dent doesn’t result in a sharp edge, and retain all or almost all of it’s strength. It’s the only material that can do that. That’s a good thing, for steel.
In the 90’s, they experimented with bonding (gluing) aluminum, often to steel or aluminum lugs. We’ll cover lugs later, but it’s important to note: no one bonds aluminum any more, because glue doesn’t last forever. Many of these early bikes developed a weird bubbling of the glue at the joints, and became unsafe to ride as the glue dissolved. Same goes for early carbon bikes too. New ones have different problems, and but maybe we’ll see bubbles and weird solvents leaking out soon on 15 year old carbon bikes. I wouldn’t doubt it.
Aluminum’s advantages: Lightish (maybe .25-.5 lbs lighter, if you take a tough steel bike and a tough aluminum bike), easy to robot weld, looks fat and tough, cheap to buy. Disadvantages: ages poorly, doesn’t like to be dented, can’t be affordably repaired, so bikes go in the recycling bin if damaged. The advantages are mainly ideal for the seller (talking points, it’s lighter, look at my cool graphics, cheaper, shorter service life) not ideal for the end user.
Titanium is TIG welded exclusively. You can glue/bond it too, but almost all Ti these days is TIG’d. Titanium does not have the short fatigue life of Aluminum, so it has the ability to be ridden safely for years, if it is not dented. It’s an incredibly hard material, so it is hard to dent, but dents do happen. It’s hardness makes it very difficult to cut and machine, increasing the cost of any Titanium product. Welding must be done in an oxygen free environment that is very clean. Ti welds that are exposed prematurely to dirt or oxygen will fail in time. Ti bikes can be repaired, but TIG welds are hard in general to repair, and most cracked TIG bikes are scrapped no matter what the material is.
Ti is about half a pound lighter than a comparable Steel frame.
Advantages: No rust, looks nice with no paint, bling factor, marginally lighter.
Disadvantages: Cost, doesn’t dent well, hard to work with, easy to mess up during fabrication, environmental toll.
On a recent trip to a US factory where high end Carbon bikes are made, I found out why the industry loves carbon. They can say Carbon bikes are hand made, but those hands are not the hands of skilled laborers. They are just folks in a room stuffing pieces of carbon in a mold. Imagine taking a tissue and stuffing it in a dixie cup, then adding 3 more tissues. Then stick the dixie cup in the microwave. Now you know how to make a carbon bike. Carbon is all about engineering, not about workmanship. There is way more workmanship in the painting, as I saw later in the tour, where much of the paint work is still done by eyeball and hand.
Companies used to employee craftsmen and women who mitered tubes, filed things, welded things, ground metal, hand aligned frames. These people were skilled. They cost money. They had to go. Most of the bike industry is not about making great bikes. It’s about making money.
Carbon fiber bikes are made of 3 things: Sheets of fabric called carbon fiber, epoxy (glue) and small chunks of aluminum that are inserted into high wear parts of the bike, sometimes.
Carbon is placed in a mold, epoxy is injected, it’s pressurized with a bladder to squeeze out excess glue, then it’s stuck in an oven and baked. The bike is made in chunks and the chunks are later glued together.
Carbon is incredibly strong but incredibly fragile, like a guy who is huge and super tough until he sees a mouse, then he turns into a screaming wreck. Wack a carbon tube with a hammer really hard, chances are it will be fine. Scratch it with a rock that kicks up from the road, and if that scratch gets past the paint, the frame could be knackered. When it fails, it generally fails without warning, catastrophically. Think of a glass you drop 3 times. First two times its fine. 3rd time you spend the next 10 minutes sweeping up shards of glass.
We don’t fully understand carbon fiber and how long it will last or how strong it is. When that new giant Airbus jet plane came out, I read in the Post that the engineers didn’t know how long the carbon fiber wings would last, as no one had many any that big before. That’s on a plane that carries hundreds of people across oceans. They don’t know how long it will last. If they don’t know, you know that bike engineers sure don’t know. Airplanes are tested much more brutally than any bike ever has been.
Here’s what I know, from working on Carbon bikes. IF they are well taken care of, expect about 10 years of life out of a frame, or 5 years if the headset and bottom bracket are integrated into the frame. After that, the frame/bearing interface develops play, and the frame is done, unless you want to hamburglar a beer can shim. I’ve seen two year old press fit carbon bottom bracket shells wear out. They’re happy to warranty a busted frame though, because it cost about 40 bucks to make, and you’ll need all new bearings, seatpost, maybe stem, cranks, etc to make your new frame work.
Carbon’s chief advantage lies in it’s moldability. You can make anything out of carbon, which is really handy for dual suspension bikes. Ironically, carbon and off road use are a pretty poor mix. No big deal if you race and get free bikes though.
Carbon’s advantages: Light (1.5 lbs lighter for a steel race frame and a carbon frame), cheap to make, looks racy, easy marketability, repairable in the right hands, moldability.
Disadvantages: Short service life, potential catastrophic failure mode, puts skilled labor out of a job, cost (although you’ll see that plummet in the next 5 years, and carbon bikes will be at the 500 dollar price point… not a pipe dream, I heard it from a major brand product developer who is working on said project).
Steel can be TIG welded (melted together), Brazed or Lugged. All of these have advantages and disadvantages. Let’s get Brazing out of the way first. Brazed and lugged joints have a lot in common. They both are low temperature, and involve melting brass or silver over a joint to glue it together. The melted brass forms a metallic glue. You can overheat a joint with brazing, but in general it’s a much more gentle process to melt brass. Lower temps mean you can use thinner tubing near the joint, which can lead to a better ride quality if the guy spec’ing the bike takes advantage of brazed or lug specific tubing. Rivendell takes that to it’s logical conclusion, and has steel tubing custom drawn just for their bikes. That’s at least part of the noted ride quality of a Rivendell.
Brazed joints look really smooth. Most TIG welded bikes, and all lugged bikes, have at least some raw brazing on them, usually at the drop outs or rack mounts. If you can’t really see how the tubes are put together, chances are it’s brazed.
Brazing advantages: like TIG welding, you can stick tubes together at any angle. It’s easier on the tubes, and you can use lighter tubes. It’s repairable, you just melt the brass and the tubes come apart. Disadvantages: when big tubes come together, it’s easy to make a mess and or over heat the tubes. Master brazers are rare (Nitto Racks are all Brazed, for the record, by one woman) and most people who have to braze are just serviceable at clean joints, good enough to put a rack mount on, but that’s about it.
TIG welded steel is a great set up for mountain bikes, industrial production, or when you can’t afford to hire a master brazer or develop a lug set. Wanna prototype something? TIG welding is your method of choice for it. Steel tubing companies have developed special high heat tubing that air hardens after TIG welding. This air hardening makes the tubing stronger than it was BEFORE the welding took place. TIG’d steel frames, properly designed, are incredibly strong.
Steel lasts a long time. Rivendell conservatively estimates their frames will last 25 years, but that’s an understatement for most of them. I have a ’93 Bridgestone I use as a daily rider, and there are tons of 1980’s steel bikes still on the road. My favorite bike is from the late 70’s making it about 40 years old, but it rides fantastically despite numerous dents and generally looking terrible. Steel bikes, well cared for, will last a really long time. 20-70 years.
Steel can be dented and remain strong. It can be bent and unbent. It can be poorly welded and still hold together. It can crack and fail slowly and safely, creaking before it fails completely. Crash a steel fork and the fork will bend before the steel frame, saving the frame. Bending is good. Snapping is bad. It can be infinitely recycled and when you are done with that, just put a steel frame in a field and it will eventually turn back into it’s base elements.
But… Whatsalug? Lugs are a really old way of putting tubes together. Traditionally only steel bikes were lugged, but there are lugged aluminum bikes, lugged carbon bikes, Ti carbon blend, the list goes on. Simply put, a lug is a socket that a tube goes into. The tube and the lug (socket) are bonded with brass, just like in the brazing process. They sneak the brass between the lug and the tube with flux, a soapy looking liquid that you spread on the tube and lug before sticking them together. The flux draws the brass or silver between the lug and tube.
Lugs allow for relatively easy frame repair: warm up the lug, pull the old tube out that’s damaged, put a new one in. They reinforce the tube junctures, making the joint super strong. It’s like a thick external butt. However, they allow thinner tubing to be used than TIG welding, so you can fine tune the ride quality through the use of custom drawn lug (or brazing) specific tubing.
Lugs are gorgeous. They are the best looking way to put a bike together, and even cheap crude lugs generally have a weird appeal to them. The finest lugs (we’d count Rivendell’s lugs as among the nicest ever designed) are art in and of themselves. They add strength and beauty and originality, if you are using your own lug designs. Designing and making a lug is an expensive process, however, and most small builders can not afford to make their own. A bike consists of 5 lugs, and the 3 main ones generally cost about 20,000 bucks to develop. If you make your own drop outs too, add more money. When you see a bike with proprietary and pretty lugs, factor that into the cost.
You can ID a bike with proprietary lugs without it’s paint, something you can’t do with 97% of all TIG welded bikes, no matter what material they are made of. Strip an old Peugeot, a Rivendell, a Mercian, a Waterford, and you can figure out who made if you know lugs. That’s pretty cool.
Lugs are classic but strong, smart but simple, gorgeous but practical. We sell TIG welded bikes, and like them plenty, but the lugged bikes we sell are our favorites.
Lug advantages: strong, lighter tubing can be used, repairable tubes and joints, low temperature, can make a bike unique in a way TIG welding never can.
Lug disadvantages: Cost to develop has to be passed on to consumer. Harder to paint around fancy ones. Pretty lugs can cover bad craftsmanship.