6 Open Secrets Of Aluminum Bike Frames


Aluminum bicycle frames are strong, light, and practically rust free. It is stiff enough to handle the rigors of pot-holed traffic lanes, humid summer days, rocky mountain trails, and even the weight of a small child in the backseat carrier. But like everything in life, aluminum is not indestructible. It will corrode and eventually break.

How long do aluminum brakes last in the first place?

Aluminum bike frames typicall last 8-15 years in normal use and typical weather and road conditions. A bike is reaches its end of life when the frame is dented or cracked, especially if this happens at a critical sress point. Riding your bike subjects the frame to cyclical stress, which weakens the aluminum and eventually leads to braking.

Let’s see how an aluminum bike frame ages and how much beating it can take.

Aluminum will corrode. It will not bend and reform like steel can. Aluminum does have a breaking point, and stress is handled differently with this metal, in that it holds its shape well while maintaining lightness, absorbing shock and vibration, reacting quickly to applied torque. But like everything in life there are pros and cons. Let’s take a look.

Do aluminum bike frames wear out?

Aluminum will wear out. It will break. It will corrode and it will certainly not last forever. This doesn’t mean that aluminum is a poor choice when picking out a new or used bike. It simply behaves differently than carbon fiber or steel. It also just goes to prove that time is the ultimate winner in this case: nothing lasts forever, even carbon fiber.

Do aluminum bike frames rust? 

Metal has and always will corrode. Sure, aluminum will not corrode as quickly as steel, but when it does it’s called aluminum oxide. It’s hard to notice to the naked eye. The oxidation process takes on a completely different color when compared to iron.

What we commonly refer to as rust is called iron oxide. Since aluminum doesn’t contain any iron, aluminum bikes don’t rust the same way as steel bikes do (which contain iron), but they do corrode, which results in aluminum oxide. This is a slow process, and it usually starts where the paintjob of the bike is damaged.

Its rate is largely affected by the amount and the chemical components of the water frame is exposed to. Riding in the winter affects the aluminum more than dry weather does.

Aluminum oxide transforms into an aluminum-like color, not orange or red like iron oxide. And it’s splotchy, it doesn’t flake or crumble. Aluminum is also more brittle than steel and so a dent would cause more of a compromise—like a crack—on an aluminum frame than on one made of steel. 

Flexed, dented and cracked aluminum frames

There is a scientific way of measuring the strength of a metal called the tensile strength tests. It shows how much stress metal can withstand before becoming compromised, e.g., breaking.  When discussing tensile strength, the yield is the maximum point to where metals can bend and reform to normalcy without entering the point of no return, what we call, deformation.

For example, you could be descending a steep road and hit a nasty pothole and keep on riding without noticing any damage to the wheels or frame even though they flexed and reformed while absorbing those impacts. You might get a pinch-flat, but the wheel would hold true. This is the tensile yield coming into action. The wheels did flex and bend on a small level but not to the point where they permanently deform. It’s sort of like the elasticity of a rubber band. The rubber band will stretch to a point. 

Under extreme load a bicycle rim will literally flex and reform to a perfect circle; this goes back to that tenisle strength test. If your rim goes out-of-whack after hitting a curb there’s a good chance it can be “trued” back to original shape by simply tightening and loosening the spokes.

Remember riding bmx as a kid and someone getting a taco rim? Most times you would replace some spokes to pull the wheel back to its true shape. Bike frames undergo a similar but different deformation.

How much your bike frame flexes and where its breaking point is depends on the bikes tubular wall thickness, the quality of the weld, the weight of the rider, and let’s not forget the terrain.

It is possible to weld a cracked or broken aluminum frame and to but it back into shape, but this is usually a very complicated and expensive process, which results in a weaker bike frame than the one you had in the first place. Reputable manufacturers offer lifetime guarantee on their bike frames, which means that you’re best off checking with them if they can replace the entire frame for you.

Dented aluminum bike frame: can I ride it, can I fix it?

Whether you can ride a bike with a dented frame, inspect the size and the location of the dent. If you have a golf ball-sized dent in the frame, it might prove faulty and mostly likely fail. If the dent isn’t too noticeable, like a pea-sized dent, and not residing in a key stress point, such as the top or down tube, just keep an eye on it and take it easy.

Inspect the dent, measure its length, compare it to pictures posted online of other dented aluminum frames. Remember, aluminum is not as malleable as steel. So dents and kinks are public enemy number one. And obvious signs of compromise are cracking and more bending of the tube.

At the end of the day keep an eye on it. If symptoms worsen consult your LBS (local bike shop) or start searching for a new or used frame. They are a dime-a-dozen. Remember, aluminum is the most abundant metal in the world. 

How much weight can an aluminum bike frame hold

An average aluminum bike is tested and guaranteed to hold between 275 and 325 lbs (125 – 147 kg) including the weight of the bike, rider and the cargo. The exact weight limit is usually found in the bike’s manual. Bikes made of other materials such as carbon, titanium or steel are usually designed with similar weight limits in mind.

My average work commute is around 65-85 miles a week. I weigh in at 215 lbs. and carry an additional load of about 15 lbs. (work clothes, food, water, and accessories and tools needed to repair on the side of the road in case of blowouts, broken cables, and loose spokes) I ascend and descend 4500 feet a week. The total weight is in the ballpark of about 250 lbs.

My aluminum Trek hasn’t failed me in any such way over the last 11-years. I’ve subjected that bike to over 5000 miles and counting. It’s gone through everything. From the muddy and rocky ravines of Iowa, to the road shrapnel of Connecticut, my bike has survived.

I will occasionally tighten and loosen my rear spokes after putting my 3-year old in the carrier—and with that said I’d increase the total load to 275 lbs. Still, it operates how it should with no signs of sag or creak. Keep in mind I often provide weekly maintenance including cleaning and oiling the drivetrain and tightening down various bolts as well as giving it a good bubble bath from head-to-toe.

Of course, the durability of your aluminum frame varies. As well as different variables: what is your intention with the bike? Just like steel and titanium frames, aluminum frames are welded in key stress points which hold a substantial amount of force. A poorly welded frame will result in a faulty joint, thus a compromised frame. 

Conclusion

An aluminum bike reacts quickly, carries itself lightly, and holds up against the worse mother nature can dish out. Aluminum oxide takes longer to occur than rust on iron. This is also a great time to dive yourself into cycling as gas prices rise.

There have also been so many technological advancements made in cycling and the traditional design of a bicycle has not changed for more than 100 years, but the materials and way in which the bicycle is made and assembled has, and for the better. This is literally the golden age of cycling, and aluminum frames are just as dependable and fun as any other material. Maybe except a wooden bike, but that’s a whole other article.

Happy Pedaling!

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