Love for bikes

Aluminium bike restoration: worth restoring?

When you look around for restored bikes on the ‘net, you may be surprised to see that almost all of them are steel – yes, steel bikes look better, and aluminium bikes are relatively new. But is it just that ? Why people are shying from aluminium bikes, or at least, restoring them?

Aluminium bikes are mass produced since 1970s, though not as much, but there are still wonderful examples worth salvaging, like Yeti Ultimate, Nishiki Alien, even Gary Fishers that are relatively new.

Unfortunately, aluminium bikes are harder to restore compared to steel, even carbon fiber (if not shattered completely). This sounds absurd, given how cheap aluminium bikes can be, and produced almost anywhere in the world. Aluminium bikes are not always repairable, or can be a huge challenge. So, let me sum up why aluminium bikes are so unpopular when it comes to restoration:

1. Aluminium bike frames are harder to repair

Steel bikes are easier to repair for cracks, because welding steel is much more easier. In fact, most of the time, you can get away with welding altogether, and braze it. For very old, cheap steel bikes,

Triple butted top tube dimensions, taken from Colombus website. These tubes are very lightweight, strong, and easier to weld or braze due to thicker ends.

it’s even easier: no butted tubes, tubes are heavier gauge so even with mediocre welding skills, they are on the safer side to weld. Most old, cheap steel bikes does not have very complex, special alloy tubing, compared to high-end steel bikes that use special tubing like Reynolds or Colombus.

I’ve even seen some very skilled people welding steel frames with a stick welder! Of course, this is less then ideal, but it works.

Aluminium welding, even under very ideal conditions, is hard. I stick weld myself, which is nearly impossible with aluminium. I have never welded aluminium, tried MIG welding on steel with pretty decent results, and after seeing people welding aluminium, I can see it is HARD. Aluminium is not forgiving. With steel, you can determine when it’s going to melt, judging by the color. Aluminium does not change color under heat. Having much lower melting point, you quickly past the melting point, with almost no prior warning.

That doesn’t stop there. The majority of aluminium bikes have butted tubes, which are extremely thin except for the ends, and hydroformed into weird shapes. If you have a heavily damaged tube on a steel bike, you can remove it and weld another tube. With hydroformed, weirdly shaped tubes, you cannot find a replacement, even if you have the tools and skill to weld aluminium. Another problem with aluminium is finding the correct electrode to weld it. There are lots of aluminium alloys, and good luck finding the correct rod. Even if it goes well, you also need to temper it, which is another skillset to have.

Aluminium corrodes badly, which is more pronounced for older frames, due to heavier use of steel parts and poorer metallurgy. So, before you get into such endeavor, you have to check at least the frame internally. Corrosion happens where different metals mate, so check bottom brackets, seat tube and head tube for powdery residues. Another problem corrosion causes is, sticky parts: especially, seized bottom brackets. If you’ re lucky, heat, elbow grease, even impact hammers can remove stuck bottom brackets. You may end up with damaged threads, worst case, damaged tubes.

Look for dents: if the frame has butted tubes, even small dents can greatly compromise structural integrity. It’s like standing on a soda can with one foot: a small dent in the can will lead it to crush easily, while the flimsy soda can with no dents on it carry a considerable load. Same with aluminium frames…

2. Aluminium is harder to paint

Aluminium is surprisingly hard to paint, due to oxidation: Aluminium has an oxidised layer on top which you can’t see, unlike steel. This is basically “rust”. Most people use spray cans to paint bikes. Spray on primer is generally acrylic filler primer. Such primers won’t adhere to aluminium. You’ll need an etching primer, which includes acids, hence the name “etching”. Or, epoxy. I’ve never seen

This is a pretty cheap, MTB frame made by God-knows-who Chinese maker. The original paint was crap, so I removed it completely, which revealed a “surprise”: smooth welds, with body filler. Normally, this is done by filing / sanding the first bead line, then re-welding over it. I think this is more robust then re-welding over the weld. This particular frame has nothing special, no sentimental or technical value. I just have lots of parts lying around, and need a “backup” MTB, so I decided to repaint it. Then it becomes a “project”, as I also have a very old Rock Shock SID needs huge amounts of “service”.

epoxy primer in a can. I doubt they ever exist, because epoxy primers are mixed with hardeners prior to use.

I know one etching primer in spray can form, made by Sikkens, and it was very expensive at the time. They are rare, and surprisingly hard to find. Most of it, due to, older-generation etch primers are super toxic. Newer generations are using different chemicals obviously, that’s why they are so expensive. Epoxy is not better. If you have a compressor and a paint gun, you have more alternatives. Much more. I paint almost anything with rattle cans with varying success – mostly due to each type of rattle can is different. It’s the inconsistency that matters; which I hate most about rattle cans. They are also inferior compared to automotive grade paint, in every sense, and they are more expensive.

If you still want to restore an aluminium bike, at least get one with a “decent enough” paint job: you can lightly sand the old paint, prime and paint – that way, you don’t have adhesion problems, at least.

3. Aluminium frames won’t last

This is the saddest part. Of all materials used in bikes, only one is doomed to fail, and that is, aluminium. Most people believe they’ll last forever because they don’t rust. But it’s flawed from the beginning. It’s the same thing that kills otherwise perfect planes, that is metal fatigue.

A bicycle frame is a perfectly stable structure, made up of 2 trusses, used in steel railroad bridge construction. On the other hand, it still flex, making it susceptible to metal fatigue. Steel has a very strict fatigue limit, meaning when you stress it, it breaks. Up to that point, steel deforms like spring, but not weakens. At least, theoretically. For aluminium, each deformation cycle weakens it, and it will break eventually.

This is a hugely debated subject, and that does not mean steel is not entirely fatigue-proof. I’ve seen huge springs break, under years of repeated loads. There are aluminium frames with better longevity, too. But the real problem is, every material will eventually break: metals from stressing, or composites like carbon fiber from either stress, or some other condition, like ozone attacking resins, or prolonged UV exposure. However, both steel and even carbon fiber is very repairable, while aluminium is not, for the reasons I talked about.

I’ve seen people complaining about their frames losing its stiffness over time, but I suspect they either get stronger to flex the bike, or just got fatter. Anyway, it will eventually fail – some say good MTB aluminium frames are only good for 10.000 kms. I doubt that for many reasons. An MTB ridden to home from work will not stress much as the one used for cross country. Tire pressure, suspension stiffness, rider weight, road conditions, and even where you store your bike matters.

4. They look like each other

I probably wouldn’t notice the difference if someone gets my bike, and replaces the frame from some other manufacturer of the same era, replicating the paint job. There are not so much distinct frames made up from aluminium. Almost every brand outsourced the production to China or Taiwan, Merida and Giant makes frames for premium brands we all know.

In the past, bikes were more utilitarian things. It was not strange to find eyelets and mounts for chain guards, mudguards, and other usual stuff, even in the high-end bikes. Components were heavier and generally lasted longer, so it was worthwhile to make them look nicer. Your aluminium bike probably doesn’t look like a nice vintage bike. Also, a vintage bike restomod would be even more fruitful; combining gorgeous look of a vintage bike and versatility of modern components.

Shimano and SRAM almost wiped away every other major component maker beginning from the start of the millennium. Luckily, there seems to be more choice these days, thanks to boutique brands and Chinese manufacturers gaining traction. But regarding 2000’s were almost flooded with look-alike hardtails and road bikes, it’s not easy to find an aluminium bike that is worth the effort.


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