7005 is an aluminium alloy used bicycle frames, due to its relative ease of welding it does not require expensive heat treating – it is however harder to form making manufacture more challenging.

It has an Ultimate Tensile Strength of 350MPa, a Fatigue Strength of 150MPa and a density of 2.78g/cm³ compared to a Ultimate Tensile Strength of 310MPa and Fatigue Strength of 96.5 MPa and a density of 2.70g/cm³ for 6061 aluminium alloy.

It does not need to be precipitation hardened, unlike 6061, but can be cooled in air.

There are two main reasons why 6061 and 7005 are the most used aluminum alloys in cycling industry: their availability and their properties. Two other alloys, 6066 and 6069 are also used, but on a smaller scale, at least nowadays. Even scandium frames were actually aluminum frames alloyed with a small amount of scandium, and still remained too expensive. There are also other types of aluminum, such as 7075 and 2014 which are very strong, but almost impossible to weld.

6061 is an alloy that consists of aluminum, magnesium and silicone and is considered to be superior to 7005, made of aluminum and zinc, although the latter appears to be more resistant. 7005 aluminum has a resistance to failure of 51,000 psi, compared to the 45,000 psi recorded for 6061 aluminum while also being more resistant to squeeze.  However, these are just laboratory obtained data, after tests performed on different aluminum tubes. When it comes to bicycles frames, the differences between the levels of resistance are also influenced by factors such as welding quality, tube shaping and thickness.

Experience has proved that there are indeed differences between 6061 and 7005 alloys but they are hardly to be taken into account. It’s very unlikely that a usual cyclist will ever put his frame to such pressure that the limits of the two alloys will come into play.

But then, why is 6061 considered superior to 7005? Because the 6061 alloy is easier to handle, reducing frames production costs. Basically, 6061 aluminum allows manufacturers to obtain lighter frames which are also better designed. And last but not least technologies and machinery needed to process 6061 alloys have become cheaper in recent years, which has some obvious implications.