My first bike in 1992 was a Trek 820 mountain bike. Fully rigid, chromoly frame, 21 speed. Basically, if it had a larger wheelset, it was pretty much the gravel bike I ride now, over 20 years later. Fully rigid, chromoly frame, 11 speed. In ’92, I remember rolling down fire roads, double track and single track. Basically, gravel biking before gravel biking was cool. And those memories that I made then, now come back everytime I get out on my 29″ Breezer, rolling down double track, single track and gravel roads.
Since that time in 1992, I’ve had exclusively aluminum frames prior to getting into gravel riding and bike-packing. They’re a very different feel, ride quality and responsiveness. Is one better than the other? Yes, they both are. Is one better over the other in all categories? No, neither of them are. Does this mean you need more than one bike? Hahaha, well, yes. Or, at least, maybe…
In this blog, we will explore the many differences between the two materials, and discover which one is better for you, depending on the riding you wanting to do. If there is a perfect, “do-all” bike out there that is great in all aspects, I haven’t heard of it. But I can guarantee that there is a perfect “do-what-you-need” bike for your riding.
Understanding Chromoly and Aluminum Frames
Chromoly is a steel alloy made of chromium and molybdenum. It became popular with frame builders due to it’s ability to be heated without deforming or weakening. It was stronger than steel, and had better weather resistance.
Chromoly has been a long time favourite due to it’s durability and resilience. It has a compliancy that no other material can match, making it a great choice for those who spend long miles in the saddle.
Categories such as gravel biking, long distance touring and bike-packing have all chosen chromoly as their frame of choice more often than not. Some long distance tourers have stated that if something were to go wrong with their frame, most metal workers in most smaller towns are more than capable to weld and fix chromoly and that’s reason enough to stick with this material.
Aluminum, by contrast, has a much better stiffness-to-weight ratio. Frame designers using Aluminum are able to create better tubing designs to achieve their desired outcomes, creating bikes that are very responsive due to their stiffness and yet lightweight. And better yet, they don’t rust!
One of the biggest advantages of the lighter weight aluminum frames is speed. Aluminum frames are faster, partially because they are lighter but also because of their stiff nature. Under high speeds and heavy output loads (such as sprinting), aluminum frames hold up without flex, creating more efficient power transfer.
Aluminum quickly became the frame of choice for racing. Road bike racing and mountain bike racing both saw immediate benefits. Today, most road bikes and mountain bikes you see will be made of aluminum. Gravel biking, touring and bike-packing applications are also still often using aluminum when speed and performance are more valued than durability and comfort.
Pros and Cons: Chromoly vs. Aluminum Gravel Bikes
Chromoly Gravel Bikes
- Superior durability for long-term use.
- Absorption of vibrations for a smoother ride.
- Ideal for loaded touring and bike-packing due to its robustness.
- Relatively heavier compared to aluminum bikes.
- Potential for rust if not adequately protected.
Aluminum Gravel Bikes
- Lightweight design for enhanced speed and agility.
- Stiffer frame offers efficient power transfer.
- Resistance to rust and corrosion
- Less forgiving on bumpy terrains compared to chromoly.
- May transmit more vibrations, leading to potential discomfort on longer rides.
Choosing the Right Bike for Your Adventure
Factors to Consider
So which frame material is right for you? In order to answer that question, you must first answer some other ones. Such as what type of terrain will you be riding on? And how long? For how far? How much gear will you be packing along with you?
If you want to race, or just speed in general is what you seek, an aluminum frame is a great choice. Most aluminum gravel bikes still have many mounting options for bags and racks. In addition, tire sizes are generally narrower on these bikes, ranging from 40-47mm. A narrower tire will be faster. However, you do sacrifice comfort for this speed. On a recent gravel ride with a friend of mine, me riding a chromoly gravel bike and she on her aluminum gravel bike, she made the comment that the road was making her “teeth rattle out of her head”. I hadn’t noticed.
A chromoly frame often is built for more distance riding and therefore will often contain larger tire sizes. Such as my Breezer Radar X which has 29″x2.25″ tires, essentially the same found on many mountain bikes. This gives the bike an extremely stable ride over gravel, allowing it to float over loose gravel and absorb a lot of the small, continuous bumps to enable a more comfortable ride so I can ride longer.
Ultimately, the best bike for you will be determined by answering those questions, but then by test rides and consultations with your local bike shop to understand the best fit for your purposes
Essentially, the biggest differences you will find between the two are that chromoly is compliant and comfortable while aluminum is light and fast.
As you consider your new gravel bike, think about a few things. One, will you be riding in a group, two, what are your local roads like and, three, how long do you want your rides to be?
Long distance touring on an aluminum frame will be rough. And the minor weight savings you may have gained will pale once you load it up. But, on the other hand, if you’re out for speed or if the group you’re joining is out for speed, a chromoly frame will frustrate you!
Have Your Say
Of course, maybe you’re reading this and want to make sure I hear your opinion! Please, add some conversation in the comments section. Let me know your favorite choice and why. Let me know why you maybe agree or disagree with me here. Or, better yet, talk about your bike and your adventures! Of course, share some pics too.