Should you look for a specific frame material? Often times this is dictated by budget - most commonly the choice is carbon vs aluminum. Remember: not all carbon fiber is equal nor is all aluminum equal. Tubing shape, wall thickness, construction methods and layup (for carbon fiber) differ between bikes and across manufacturers. Naturally, manufacturers put a lot of emphasis on these differences in their marketing materials. Most of their claims should be taken with a grain of salt, nonetheless there is often a kernel of truth behind the claims. Aside from minor differences, with similar components an aluminum frame will always be cheaper than a high-performance carbon fiber frame. However there are situations in which frame material is important to consider for other reasons. Fast gravel riding? A nice supple frame made of carbon fiber or titanium might save some weight and have excellent vibration damping properties. For bikepacking or touring, an ultralight carbon fiber bike may not be the best choice to handle all that weight. Instead, the toughness of steel or titanium might be better. For a commuting bike which will be exposed to rain and road salt in the winter, rust-free aluminum or an inexpensive steel frame would be reasonable options. If you are looking for the absolute lightest and best performing aero road or aero gravel bike, at any cost, very high performance carbon fiber is the obvious choice.

When we are angling for the best performance, we usually opt for the lightest bike that fits into the budget. At the high end, this is invariably carbon fiber as noted previously. In the midrange, the most refined aluminum frames compete directly on weight with frames made from lower-to-mid-range carbon fiber composite materials…and the aluminum frame tends to be much less expensive. A very well designed aluminum frame with good component choices can be a very lightweight package at reasonable cost…and ride very well, too.

A good example is the Trek Emonda. Although I have no particular allegiance to Trek (the last one I bought was in the late 80's), they certainly represent the range and scope of what is typical among the large brands and what most of us will see in stores. As of late 2023 there were 17 versions of the Emonda on their website, plus the option to purchase only framesets (frame + fork). In Trek's lineup, the Emonda is their lightweight, all-around road bike. There are versions made from aluminum, mid-range carbon fiber, and extra-light/extra-stiff carbon fiber. For each of these three frame materials/layups there are multiple versions of the bike with different drivetrain and wheels, and priced accordingly. Let's look at three examples of the Emonda: The ALR 5, SL 5 and SLR 9. The complete ALR 5 retails for approximately $2300 (19.9#) while a complete Emonda SL 5 (19.6#) is $3400. They weigh essentially the same, so what does an extra $1100 get you? Both of these versions come with an 11 speed Shimano 105 mechanical drivetrain with hydraulic disc brakes and both have a carbon fiber fork. The SL frame is very slightly lighter, however since it's carbon it is substantially more expensive than aluminum. Does the carbon fiber frame ride better? Is it stiffer or have better vibration damping? They may advertise it as such, but really only the rider can judge. Is a middle-of-the-road carbon frame worth an extra $1100 over an extremely well-designed aluminum one? Probably not. The SLR 9, at the highest price point, might be quite a different riding experience than these other two. It is made with Trek's "best" carbon fiber which usually means it is stiffer with a more efficient layup, indicating a more lightweight frame. It includes SRAM's lightest, best, electronic wireless 2x12 drivetrain, some super nice wheels, and a fully hidden internal/integrated brake lines (may or may not be a good thing, depending who you ask). This bike is definitely lighter than the less costly versions, at around 14.5 pounds, but the price tag is an eye-watering $13,000. Aspirational for most of us mortals, to be sure, but undoubtedly an excellent bike to ride. Personally for that price, I would rather purchase a carbon fiber frame from a custom framebuilder. Perhaps a middling option like the SL 6 Pro version with carbon frame and an electronic Shimano 12-speed drivetrain for $4,999 might be a more reasonable option.

Above: All four of these bikes are Trek Émondas. Top left is the Émonda ALR 5, with an aluminum frame and sensible component choices. An excellent value. Top right is the SL 5 version with a slightly lighter carbon frame, perhaps for a smoother ride, and again with component choices meant to function well and stay within budget. Bottom left is the top-of-the-line SLR 9 version of the Émonda with Trek's mostly highly-refined carbon fiber frame meant to be as lightweight as possible, comfortable, and with less regard for cost. Components are similarly top-notch with performance, rather than cost, being the highest priority. Bottom right is an Émonda available as a frameset only (frame + fork); same frame as the SLR. Buying a frame allows one the most freedom in component choices, although this almost always comes at a higher cost than buying a complete bike. Although all of these bikes - and the other 10 or so version of the same bike - have similar geometry and handling characteristics, they differ in frame material, weight, and cost.

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