You’re building a bicycle and you want to buy an aluminum frame for it. However, you’ve also read or heard that bicycle frames made of aluminum aren’t very durable and will eventually crack.
Is that true? Do aluminum bike frames crack?
Aluminum bicycle frames are lightweight and affordable, but they’re also weak. An aluminum bicycle frame will fatigue within 5-6 years and the metal will start to crack. When that happens, the frame will need to be repaired or replaced.
Frame fatigue is real, and all bicycle frames inevitably wear out. In this post, we will talk about why aluminum frames wear out faster than their counterparts made of other metals and composites do—and what it means for you as a bike owner.
Do Aluminum Bicycle Frames Crack?
Think of your frame as your bicycle’s skeleton.
It’s there to hold everything together and support the combined weight of the bicycle and you, the rider.
The frame is connected to your bike’s wheels, with or without suspension, so it absorbs a great deal of the shocks and vibrations from the bumps, potholes, and pebbles you ride over on the road.
In the case of BMX (for smooth surfaces) and MTB bikes (for rough terrain), the frame is also stressed by jumping, pumping, climbing, riding downhill, sharp turns, and fast braking, putting a lot of strain on the material.
Add to that the occasional dent from your bike falling to the floor or you crashing with it, and it isn’t hard to understand why a frame would sooner or later wear out and need to be repaired or replaced.
When an aluminum bike frame reaches its final stage of wear and tear and/or is pushed to its limits, it cracks.
And Do They Crack Easily?
The answer depends as much on the rider and the terrain as it does on the frame.
Some riders can go for years, sometimes a decade without dinging, denting, cracking, or breaking their bicycle’s aluminum frame. Others, especially if they take their cycling to the extremes, can mangle their frame beyond repair in as little as a couple of years.
Aluminum is a good material for a bicycle frame because it’s lightweight, economical, and, unlike steel, it doesn’t rust and can be worked into all sorts of aerodynamic shapes (or, in the case of mountain bikes, shapes that require resilience and durability).
However, instead of softening the shocks and vibrations from the road, aluminum transmits them to you and to the bike’s parts. An aluminum frame feels “dead,” in a way, and can make your ride much more uncomfortable than a steel, carbon, or titanium frame.
For the same reasons, it wears out quicker than them.
Related: How Long Do Bicycle Frames Last?
If They Crack, Can They Be Repaired?
It depends on the severity and the location of the crack.
Each tube on a frame has its own purpose and is subject to different forces than its counterparts.
The top tube, for example, is subject to the force of compression and, when it’s weakened, dented, or cracked, is prone to buckling. The downtube is subject to tension, so it won’t buckle, but it can still crack.
If your frame gets cracked, don’t ride the bike and take it to an experienced framebuilder. They can help you weigh the ups, downs, cost, and risks of repairing the frame versus replacing it with a new one.
Related: Where Do Bicycle Frames Crack?
Aluminum frames can be welded, but the question is whether it’s even worth it. After a fall, crash, or years of wear and tear, it’s very likely that the crack isn’t the only place where the frame is damaged.
One of the advantages of building a bike with an aluminum frame is that it won’t break the bank. Which means you won’t feel guilty to swap it out with a new one if the frame cracks due to wear and tear or you crash the bike and it gets mangled beyond repair.
So Should You Get One?
When building a bike, everything is a trade-off. (And the frame is no exception.)
When it comes to the frame, your options are, from lowest to highest-priced, aluminum, steel, carbon fiber, or titanium. Aside from the price, which shouldn’t be the only factor, each frame material has its pros and cons that make it a good or bad choice for your needs.
Aluminum frames, as we already touched on, are cheap, lightweight, and aerodynamic. For most bikes, they’re the type of frame that does the job, and does it well enough and long enough to be worth the money.
Steel frames have been around since the bicycle was invented, and will probably be around for decades to come. They are stiff, strong, reasonably priced, and come as all sorts of alloys and designs for different kinds of cycling.
Carbon frames are made of a composite material—carbon fibers glued together with epoxy resin—and not metal. They don’t come cheap, but they’re light, deliver a smooth ride, and offer superior performance. They don’t crack; they break when worn and torn or subjected to stress.
Titanium frames are very expensive compared to other metals, so they’re not suitable for every cyclist. Those who can afford to splurge on titanium get a metal frame that’s lively, has just the right amount of bend and flex, and can last well over a decade without rusting.
Aluminum vs. Steel Frame
If you’re thinking about buying an aluminum frame for your bike, your nearest alternative, although pricier, will be a steel frame. Also, the frames are rarely made out of pure aluminum or steel.
Instead, they’re alloys because the main metal is mixed with other metals to make the frame lighter, give it more strength, and better protection against corrosion and/or rust (aluminum corrodes; steel corrodes and rusts).
A good rule of thumb is to go for aluminum if you want a frame that’s cheap and lightweight, and you’re not too concerned about durability. However, if you want a frame that’s sturdier and easier to repair, if heavier and pricier, opt for steel.
The Bottom Line
Aluminum bicycle frames can crack, but they can’t always be repaired.
Compared to steel, carbon, and titanium frames—all of which are more expensive—aluminum frames also wear out and need to be replaced quicker.
And yet, this doesn’t stop bicycle manufacturers and bicycle owners from opting for aluminum frames. They’re affordable, lightweight, and aerodynamic, and can be mixed with other metals in an alloy for extra strength and durability.