Aluminum might be the best frame material

In the tradition of frame materials, steel is romantic, titanium is magic and carbon fiber is a super material. Aluminum, on the other hand, is… what? While aluminum is widely used — from sub-$100 balance bikes to $10,000 e-cargo bikes — it’s often cast in a negative light: it’s cheap, it’s tough, it’s tough. is brittle or not durable. And that’s not fair, because aluminum is a miracle material that deserves some respect.

“It’s a combination of materials and engineering, design and technique”

Even Richard Sachs, perhaps the most renowned living steel frame builder in the world, is a fan of aluminum frames. Sachs had an aluminum Gaulzetti Corsa – “had” because the frame was damaged when Sachs and an SUV met at Asbury Park. The bike had big aluminum tubes, a sloping top tube, BB30, integrated seat mast, carbon fork, and “one of those wacky big headsets.” Even though it was entirely different from the bikes he builds, Sachs loved Gaulzetti. And not because it was or wasn’t aluminum; Sachs liked it because it fit well and rode well. “It was so opposite to everything I do, but the actual ride was a mirror image of what I do for myself. It was the touchpoints of my riding position merged with a rational frame design As for how the Corsa behaves compared to his bikes, Sachs says: “I couldn’t tell or feel any difference.” That’s a statement that is likely to make the jaws of traditionalists drop the world over.

Improving strength and durability in weld areas, without overloading the rest of the frame, is key to making a great aluminum frame.

Trevor Raab

All frame materials have their upsides and downsides. But even among common materials, aluminum is unique. It is plentiful and reasonably priced. When used correctly it has a great feel and it has a mix of properties well suited to bike frames. Aluminum frames have won everything from the Tours de France to the Downhill World Championships.

At 1/3 the density of steel and about half the density of titanium, aluminum is a popular material in any application where weight matters. Airplane — aluminum all day. The Saturn V rocket that took astronauts to the Moon? Mainly aluminum. So it’s only natural that cyclists – who have an obsession with weight – also find it an attractive frame material.

Although aluminum is light, weight is only one property, and the other metallurgical properties of aluminum require different design approaches than steel. You may be surprised to learn that early aluminum frames – Alan and Vitus for example – were flexible. This is because aluminum is less stiff than titanium or steel, so when builders of the day learned about the diameters of steel tubing and substituted aluminum tubing, the resulting frames were soft.

Aluminum’s elongation (how far can it bend before breaking) and its endurance limit (how many times it can bend before breaking) are also lower than those of titanium or aluminum. steel. But aluminum’s low density helps it compensate for deficits in other properties. Because it is less dense, you can use more of it to compensate for its lower stiffness and strength without adding much weight.

The next big evolution came when Cannondale and Klein increased tube diameters well above steel standards. Aluminum frames have become stiffer and stronger. This is when aluminum became famous for its stiffness and infamous for its harsh ride feel.

Although it had a rocky start, aluminum’s light weight, combined with its relatively low cost and ease of manufacture, was an irresistible attraction. People have continued to experiment and improve aluminum frame designs and technologies.

go sprint
The Specialized Allez Sprint is one of the most advanced aluminum frames.

Trevor Raab

One of the names most associated with modern aluminum bike frames is Chuck Teixeira. Since 2011, he has been a senior concept engineer at Specialized; helping to develop products made of multiple materials, including the new Allez Sprint aluminum frame. Prior to Specialized, Teixeira spent 28 years at Easton, before becoming director of engineering, specializing in aluminum products. His tasks included product development, process development and thermal development. It was Teixeira who developed the revolutionary Easton ProGram and Taperwall aluminum tube sets, which in their day reached new heights in terms of weight, comfort, stiffness and durability. He knows aluminum better than anyone.

During our interview, Teixeira admitted, “Old opinions die hard,” regarding the stereotypical disadvantages of aluminum. We spent a lot of time discussing the importance of proper design and how aluminum – more so than titanium or steel – requires proper design and execution or it will “bite you in the ass”.

“It’s not just the material,” he said. “It’s a combination of materials and engineering, design and techniques.” It is a better design brought about by the accumulation of knowledge, as well as technological advancements. As a result, today’s aluminum bikes have little in common with original aluminum frames: “We understand the system better. We use more advanced techniques.

The challenge of building a large aluminum frame, Teixeira says, comes down to the welds. In steel or titanium, weld areas can be almost as strong as the tubes themselves. But when you weld aluminum, you lose strength in that area. “You lose a lot in that – you have to engineer for that. That’s why you do butting, that’s why you do hydroforming, that’s why you do complex gussets and other techniques to buttress this,” he said.

Teixeira explained that the low density of aluminum provides designers with plenty of materials to work with. “You can move it around the system. You have a weak point or a high stress point, and you can put a lot of material there. With titanium and steel, when you’re dealing with a density two to three times that of aluminum, you don’t have much to do. You run out of materials because the thing will get too heavy.

More than other metals, aluminum has benefited from the adoption of butted or variable-wall-thickness tubing. This puts more material where it’s needed for strength, but removes material where strength is less of a concern. The adoption of butted tubing was a huge step forward for aluminum, not because it made aluminum frames lighter or stronger, but because it added more flexibility in less stressed areas, which improved driving. Another huge leap in aluminum performance came with the advent of hydroforming (using pressurized oil to create complex tube shapes). Hydroforming (combined with the ease of machining aluminum) puts it second only to carbon in its ability to be shaped and tuned. That’s why aluminum frames can approach the performance and weight of carbon fiber, but at lower prices.

black heart allroad al
The BlackHeart Allroad AL is a great value and great road bike.

Trevor Raab

A frame’s head tube and bottom bracket have the highest strength requirements. So in these areas, an aluminum frame must be stiff (to reduce flex that leads to fatigue failure) and oversized (due to loss of strength after welding). But many other areas of the framework do not have these requirements. “In the middle of the tube is where the magic and the science really happens,” Teixeira said.

Of former Kleins and Cannondales, Teixeira says, “[Those tubes] were reinforced, hard, stiff and strong everywhere. Multiply that by the seven tubes of the bike and all of a sudden you have a losing combination. It might be light and strong enough, but it’s just tough. In contrast, today’s aluminum bikes only have this stiffness, strength and reinforcement in the areas of the tube where it’s needed, while the rest of the tube “can be flexible, it can be soft, it can be anything you want it to be because strength and stiffness aren’t as important,” he said.

The diversity of styles and prices also affects the perception of aluminum. Because it’s so ubiquitous, some view the material as cheap, not high-tech. That—because it’s used to make beer cans and $99 balance bikes—is somewhat substandard material for a $3,300 Cannondale CAAD13. This perception apparently doesn’t stick with steel, even though it’s the material of choice when you want to build inferior bikes. But there are different aluminum alloys (and steels), different levels of engineering and craftsmanship, and more or less attention to detail.

All the work that Teixeira and others have done, and the resulting evolution and advancement of knowledge, has paid off. Even lower-cost bikes are reaping the benefits of all the work that goes into improving aluminum: a $560 Giant Escape 3 has a butted aluminum frame, something that was once an exotic tube set for top performing bikes. Today’s aluminum frames are stronger and ride smoother while maintaining low weight and high stiffness (the right kind of stiffness). It bears mentioning again that because aluminum is plentiful, inexpensive, and easy to handle, aluminum is the most common and diverse frame material today, both in terms of price and style of bike.

So I’m here to tell you to stop picking on aluminum. Modern aluminum is underrated and doesn’t get the respect it deserves. After researching it, thinking about it, and riding it on a ton of bikes, I think aluminum is – from low end to high end, and balance bikes to cargo bikes and everything in between – the best material for bicycle frames.

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