This post is about why aluminium rims are shit.
The other day, I went to consult a bicycle fundi who is famous around these parts about the repairs and upgrades I could perform on a bicycle I happened to have on me at the time. The bicycle's frame is made of aluminium and the rims are made of steel. He quoted everything that I would require to put it in tip-top (not the petroleum jelly) shape and I said, "Yes. I will look for the money."
Two questions raised my suspicions, though. The first was whether he could perform said repairs bit by bit as the money streamed in, and he said, "No." The second time, he mentioned that he would like to replace my shiny steel rims with aluminium ones which he claimed would be lighter and "better". I said I preferred the steel rims and it is at this point that he mentioned that he likes to do a thorough job and that replacing the rims would necessarily be part of the job. I said that that would not be necessary because I liked the way the rims shone. He insisted. I ended up walking away from him permanently. At this point, I had not clearly thought about my preference for steel rims but now I can clearly outline the thought process from foundation to conclusion.
Aluminium is 13
Interestingly, just as stronger people are usually heavier than weak people, steel is stronger than aluminium. This is because, as chemists claim, there are a lot more electrons in steel which the atoms fight for. The atoms, being heavier, also pull more strongly at the electrons which partly contributes to the strength of steel. This is also the reason why aluminium wires are better than those made of steel.
Aluminium does not rust. This does not mean that it doesn't react with oxygen in the air. What happens is that the outer later of a piece of aluminium metal usually reacts with the oxygen in the air and forms a layer of aluminium oxide which does not wash off or dissolve in water. This makes it better than steel in that regard.
Since a steel rim is stronger than an aluminium rim, making it with a rectangular cross-section which is the most common cross-section does not easily jeopardise its ability to absorb the shocks thrown at it by the tyre or increase the chances of its breaking into two. Using a similar design on an aluminium rim is likely to subject it to cracking in a linear fashion along the line the spokes form. This has necessitated the manufacture of aluminium rims with triangular cross-sections which triangles are very, very strong.
If you want to manufacture a steel rim with a triangular cross-section, you might need to reduce the thickness of the rim, which also reduces its strength. A puncture repair will therefore damage such a rim by bending it inwards. This can also lead to the risk of the steel breaking along the spokes like in an aluminium rim with a rectangular cross-section.