Considering buying a metal frame bike and not sure what to choose?
You’ve heard of steel and aluminum bikes, but aren’t really sure what the differences are. No worries. We’re here to help.
This page will explain the key differences between these two bike frame materials and help you decide which is the best choice for your needs.
- Aluminum bikes are meant for road bikes or racing bikes. They are lighter weight and stiffer and therefore offer a better platform for performance bike riding.
- Steel bikes, in comparison, are heavier but also more durable. Because steel flexes more than aluminum, it offers more shock-absorbing comfort. Steel bikes are also stronger and more durable, making them better equipped to handle the additional weight of racks, panniers, and cargo.
Let’s take a look at the key differences between steel and aluminum bikes.
Aluminum Fabrication Methods
Calling an aluminum frame an aluminum frame is a little disingenuous. So-called aluminum frames are never pure aluminum. They are always mixed with a small percentage of other metals, hence the term alloy.
Aluminum technology has come a long way over the years. Frame manufacturers are now able to manipulate the thickness of aluminum to lighten the weight and stiffness through a process called double butting.
Through double butting, the middle of the frame’s tubes is kept thin while the ends are thicker to support the frame’s joints. The result is a frame that is lighter weight than conventional single butted aluminum frames.
A technology called hydroforming also allows aluminum frames to be shaped. Hydroforming is a process of shaping metal through the use of a mold and high-pressure fluid. The results are aluminum frames that are stronger than conventionally formed aluminum.
Aluminum is also seeing a resurgence thanks to advancements in the alloy. Specialized, Trek, and Cannondale have all recently produced bikes with a higher grade of aluminum called AL 6069-T6, which is stronger, allowing for the construction of aluminum frames with thinner tubes that are lighter and more compliant.
Steel Fabrication Methods
Steel was once the only material for bike frames until the arrival of aluminum in the 1970s and 1980s and later carbon in the 1990s. As with aluminum, not all steel frames are created equal.
Cheaper road bikes below $500 like the kind you find at a department store will use high tensile steel. The biggest quality you’ll notice with this type of steel is its immense weight.
Higher-end steel bikes use what’s known as Chromoly steel, which is referred to as CroMo for short. This is alloyed steel that has better strength properties than high tensile steel and, similar to aluminum, can be butted to make frames lighter.
It’s also surprisingly compliant as steel will flex while carbon and aluminum are much more rigid. Like aluminum, steel frames are joined through a welding process. Steel frames can also be brazed together, which is a process that involves using a filler material to join the tubes together.
Lugs, which serve as connectors at the joints of the frames, are an older process that is also still used today to give steel frames a classic look.
It’s important to note that not all steel and aluminum frames are the same. Advancements in aluminum and steel alloys have made many aluminum frames more compliant and some steel frames stiffer.
While you can rely on these general parameters in ride quality for steel vs. aluminum frames, expect ride quality to vary somewhat from one steel frame to another and from one aluminum frame to the next.
- Aluminum. For starters, because aluminum is a much stiffer material, expect the ride on an aluminum bike to be harsher. You’ll feel more of the road, but you’ll also get much more productivity with each pedal stroke because of that stiffness.
- Steel, in comparison, is much more compliant. Steel has flex to it and will bend. As such, steel does a much better job of providing shock absorption. This also means that your pedal strokes won’t be as productive because you’ll lose energy to flex.
Strength and Weight
Weight, of course, is very important when it comes to bikes. A heavier bike will be harder to propel forward and can be more difficult to handle. Climbs, especially, will be more challenging.
Steel is the heavier of the two frames. Aluminum is less dense than steel, making it lighter.
That said, advancements in both aluminum and steel technologies have decreased that weight. The two biggest steel tubing manufacturers, Reynolds and Columbus, have developed their own super steels, which are dramatically lighter than traditional steel frame bikes.
As for strength, there is a reason that soda cans are made from aluminum, and bridges are made from steel. Aluminum is not as strong as steel. In order to compensate for this lack of strength, aluminum frames are larger and thicker.
What’s the difference?
A steel frame is always cylindrical in shape and ranges between 1” to 1.5” in diameter while an aluminum frame might be a variety of different shapes ranging from round to triangular and are typically greater in diameter than 1.5”.
The strength and weight properties of steel frames vs. aluminum frames go a long way toward dictating their use.
Lightweight aluminum frames are better for race cyclists, who value speed and handling, while steel frames are better for touring cyclists, who value strength.
Durability and Repairability
The properties of both metals dictate their durability and repairability. Steel is not only the stronger of the two but also the more durable.
- Aluminum is more brittle than steel and is much more likely to break in a crash.
- Steel, on the other hand, is malleable and is much more likely to bend in the event of a crash. For these reasons, steel is significantly more durable.
In the event the frame is damaged, steel is also more easily repaired as it can simply be bent back into place.
Aluminum, when damaged, will crack, making it much more difficult to repair. And while a cracked aluminum frame is unrideable, steel frames will usually maintain their integrity through dents, scratches, and even bends.
That said, steel does have its Achilles heel, and that comes in the form of rust. Steel oxidizes much more quickly than aluminum. This factor is important to consider, especially if you live in a humid coastal area.
From an aesthetic point of view, aluminum and steel frames have considerable differences.
- Steel offers a classic racing look with narrow tubes and straight lines. They’re also characterized by a perfectly horizontal skinny flat top tube and have a distinctly old-school look.
- Aluminum. In comparison, most aluminum frame bikes have thicker tubs with varying shapes. As such, aluminum frames are more modern and sporty looking than their steel counterparts.
As most aluminum bikes are designed for racing, expect to top tubes that angle or slope downwards from the head tube to the seat tube. With advancements in aluminum technology, also expect to see more curves in aluminum frames.
As aesthetics are purely subjective, which frame is better really depends on which is more appealing to you.
Types of Bikes
So, what types of bikes can you expect to find with steel frames and aluminum frames?
Steel’s durability and strength make it the frame material of choice for touring bikes.
Touring bikes are designed to be fitted with bike racks and panniers. This means added weight. Steel frames are strong enough to handle the addition of racks without failing. Steel bikes are also more compliant, which means a more comfortable ride, which is a must for long bike tours.
That’s not to say that all steel frames are relegated to the touring class. Boutique bike manufacturers such as Pegoretti, Speedvagen, and Volare make custom steel frames.
Volare has even found a way to make a steel-framed bike light enough to earn its way back into serious race competition. The Madison-Genesis team used its Volare 953 just a couple of years ago.
Read More : Should I Get A Custom Bike?
Aluminum bikes, in comparison, are sort of a middle child among bike frame materials. Aluminum is lighter and stiffer than steel bikes, making it more appropriate for racing, but not as light or as stiff as carbon.
And while there have been recent advancements in aluminum technology that have seen a resurgence in aluminum frames at the higher end, you’ll rarely see an aluminum racing bike used in serious competition.
As such, aluminum frames are largely reserved for low to mid-range road bikes as they offer performance features for ride bike enthusiasts at a price that is much cheaper than carbon frames.
Aluminum frames have also become more popular with the rising interest in gravel bikes and bike packing. This is largely due to their lightweight and ability to carry racks and panniers.
Which Material is Right for You?
Well, it depends on what you’re looking to get out of your bike.
If you’re looking for an entry-level bike to introduce you to the world of serious road riding, then aluminum, with its lightweight and stiffness, is the choice for you.
If you’re looking for a bike to commute from point A to point B, or if you’re interested in longer rides that involve the use of bike racks and panniers, then you need the comfort and compliance of a steel frame.