Thoughts on choosing a bicycle – Frame

Materials

There is continually a debate about the merits of the various materials of bicycles. This is a brief discussion of those merits such that you may either be helped with your decision, or know where I stand and why I stock and suggest what I do.

Steel – the original and my favorite.

Steel is the classic material of construction for such rigid structures as a bicycle frame. This includes truss frames or lightweight frames for bicycles, aircraft, motorcycles and numerous other machines requiring a light rigid structure that can experience a variety of forces. The property of steel that lends to this purpose is its strength and elasticity.  In the case of a bicycle, a frame of high quality can be made quite light, strong enough to hold a heavy load, hang onto racks and bags, absorb impact, and last for many years doing so. This is done by making the steel quite thin where it will not experience excessive stress while leaving it thicker at the joints (referred to as “butted tubing”.) The combination of thin steel and its elasticity lend to a “compliance” that many (myself included) find desirable. This compliance is one of the great benefits of steel and the material is well suited to a structure that deflects, within a range of motion, countless times. The springs in the suspension of your car are steel for good reason. Another consideration: if your frame or fork were to fail, it is likely that is would fail in a way that is less “catastrophic” than other materials may be, specifically carbon fiber and aluminum.

Noted by some travelers is the repair-ability of steel; most anywhere in the world, someone can be found who could weld a temporary repair to a steel frame to keep you moving. I don’t think this is a substantial factor for most, but nice to consider if the further reaches are your destination.

Steel, if not stainless, is prone to rust. If you run your bicycle in wet conditions and especially if you expose it to the salt on our local roads, it will need care to prevent this. Many of the large manufacturers do a good job on paint and coat the inside of the frames with something to help prevent this, but it is not a perfect solution.

Steel is very recyclable.

Aluminum

Aluminum is a great material for many things; it is about a third the density of steel and fairly strong. You will find it most anywhere on a bike that needs a rigid solid structure—stems, hubs, crank arms, etc. It can be made into very nice, light, and possibly inexpensive bicycle frames that serve their purpose well. There can presumably, with engineering, be a level of compliance as well as stiffness in the directions needed. The material is not free of corrosion, but may outperform a steel bike of equal treatment in that regard.

I do not sell aluminum frames in general. The engineering of an aluminum frame is, in my view, to overcome some of the deficits of the material and its suitability for the purpose with less gain than would warrant such effort. You will often find aluminum frames with “hydro-formed” tubing of shapes only describable by computer code and only produced by special equipment. In fact, one of the major suppliers of aluminum frames to high-end bicycle companies has eliminated the human hand from the welding process. The end result is a frame that has properties closer to a steel frame, while possibly lighter, that is made of a material that has an elasticity lower than a comparable steel frame. The aluminum cannot deflect the same amount the same number of times, generally speaking, without failure. Aluminum structures, when designed with weight in mind and subjected to vibration and impact do seem prone to cracking – not that aluminum bikes are cracking left and right, it is simply more common. A manifestation of this is that older aluminum bikes seem to hold a lower value than comparable older steel bikes. All of the engineering challenges of aluminum can likely be overcome—but you will likely end up with an ugly bike.

Aluminum is readily recycled. That said, bicycles are generally not made from the product, rather the new stuff.

Carbon

Carbon fiber is taking over the high end of bicycles of most flavors—road, mountain and gravel. It is obviously well liked by many. The weight savings are countered, however, by significant drawbacks.

The premise of carbon fiber bicycles is to engineer every aspect of the product: strength where you want it, and no wasted weight where you don’t. Using the orientation of fibers in predetermined ways in conjuction with shape and thickness, such a bike can be made with highly tuned riding qualities and very little weight. The sophisticated “lay-up” of these fibers glued together with epoxy resin can result in compliance where you want it and rigidity where you want it and so on. While there are a few elite athletes for whom this may represent a worthy advantage, most are trading away values they have not considered for a perceived benefit. These frames are likely destined for the landfill before others – and not just because the others can be recycled. This kind of super engineered structure applied to bicycles is similar to so many of the fleeting hyper-engineered products in our lives. I see the bicycle as a tool that will hopefully endure over the years, and later be commissioned as something else: a commuter, loaner, ‘kid going to college needs a bike’. This hyper-specificity of strength of such outwardly delicate material results in a bicycle that might not be trusted after a small impact with a hard object, cannot be seen as a long term investment being locked to a pole in the city and knocked around in the garage. It is a specialized piece of equipment, and like a theodolite, might be best sold with a case. I am aware that this material is in common use and rides are not ending with a broken frame, but if a carbon bike and I part ways on a mountain ride fumble, I would never again trust its structure.

I feel that there is a good reason for the industry to move towards carbon; it is going to get cheap. The person who makes your frame is likely a low skill worker, and the bike can be fairly light with less expensive components.

Carbon fiber is very NOT recyclable.

Titanium

Titanium is pretty ultimate in some ways, but it is expensive. It is not a rare element, but turning it into a metal is an expensive process. Given the weight to strength ratio and the density, it can be seen in a simplistic way as lighter than steel for the same strength. The design of a titanium frame is quite similar to that of a steel bike: relatively small diameter butted (or not) tubing, at a reduced weight. The fact that it is so resistant to corrosion is one of the most appealing aspects to me; you will often find them sold unpainted. I would consider seeking out a titanium frame if you were 100% certain, in perpetuity, of what you want, and had extra money kickin around. (I would never be 100% certain in perpetuity of a frame, so I will choose steel and have money for a new frame when something neat comes around.)

Titanium is super recyclable.

Steel Construction

The old bikes were made by socketing the tubes into “lugs,” bringing strength where needed at the joints, and adding only a relatively low heat to the frame to join the tubes. These cast lugs constrained the design to the lugs made. An alternative was “fillet brazing” whereby the steel tubes were joined with a brass material that was built up at the joint enough to supply a similar strength. These methods are employed in some of the best bikes created, but they tend to require more skill than the market desires in the cost of a bicycle. The more common method of joining tubing in bicycle frames now (for steel, aluminum, and titanium) is TIG welding. This process creates a very strong and clean joint, though it does add a lot of heat and does not give the same reduction of stresses to the tubing that the former methods do. That said, the tubing is engineered for this method and the results are, at this point, on par.

The production of steel frames is done, generally, quite well by custom makers all over the world and at scale in Taiwan. The major manufacturers that I sell are generally sourcing bike frames made in Taiwan using good Chromoly Steels TIG welded together. Frame failure is uncommon.

Weight and other considerations

Weight, or lack thereof, is an attribute of bicycles that is heavily ‘weighted’ in choice of frame and components and constitutes an enormous cost of some bicycles. While there are some at the extreme of weight conscious (“weight weenies”); the decision of what to purchase should really be a nuanced contemplation of function, considerations of what businesses and companies you are supporting, durability, cost, aesthetics and weight. Weight, while significant, must be kept in context and considered carefully with the other factors. Function obviously comes first, but determining where you stand on weight versus durability, cost or ‘where it comes from’ is not so clear. Needless to say much of this becomes quite subjective.

If your riding is not, generally, consisting of hills for example weight is not so much of a concern. If you participate in hill climbing competitions however, it may be of greater importance than durability.

Generally, for most of us riding for transportation on smooth surfaces, it can be considered as a matter of utility rather than a serious factor in riding. One often needs to carry a bicycle up stairs, lift onto a car rack, or swing it into a bike rack – these actions can be hard on your back or just not possible with a heavy bike – especially in a country not accommodating of bicycles as a true form of transport.

Where to save weight – The weight of some components have a greater impact on your riding enjoyment than others. A heavy set of wheels and tires on flat ground roll just fine, but a loss of weight here does liven up a bike quite a bit. This doesn’t mean that a $2000 set of carbon wheels is needed, consider appropriate good tires, a good quality alloy rim, butted spokes and a quality hub. Velocity brand rims are made in USA and are very good quality – I prefer these to most.

With some exceptions, the frame of a good quality bicycle is rarely that which makes the bike feel “heavy”. I have interacted with numerous individuals that feel as though they “choose” a light bike by the frame material and this is simply not the case for most of our budgets. With money to burn I could build a steel bicycle to be less than 16lbs. Yes, the carbon bike might weigh a tad less, but I don’t believe that it matters at that point – then you may have to contemplate your sunglasses. My experience has been that the marketing of bicycles has brought many to the market with reasonably lightweight aluminum frames coupled with cost-cutting components. The purchaser of these bikes would have been much better served from an inexpensive steel frame and better components.