Rust on a bike chain is not a bad thing, unless you don’t do something about it.
Rust implies the bike has been used in wet conditions, or the bicycle has been standing in an environment with high humidity. This could be a outside and exposed, but also a shed, or in the same room where you do your laundry.
Are bike chains rust proof?
No, bike chains are not rust proof. The far majority of bicycle chains are made of metal, and there’s really no reason to use any other material.
Metal is incredibly strong and exceptionally well-suited for bicycle chains, but it’s also prone to rusting.
Although chains might be nickel-plated on the outside, which is a rust-deterrent, most of the rust happens on the surface of the rollers. These areas get into contact with the cassette/sprocket and chainring wearing away any rust-protection.
What happens if you ride a bike with a rusty chain?
The most common reason your chain is rusty is because you’ve been riding in the rain. While rust is not a bad thing per se, riding with a rusty chain is. That’s because the chain no longer has any lubricants.
If you keep on riding with a non-lubricated, dirty, rusty chain, the wear on the chain, cassette, and chainring is about ten times as much as riding with a clean, well-lubricated chain.
How does a rusty bike chain affect a bike’s performance?
A rusty bike chain doesn’t impair a bike’s performance, unless the chain is rusted to the point where the individual links are stuck and no longer move. If that’s the case, they can no longer rotate around the rear sprocket and front chainring.
If you have a bike with a rear derailleur and cassette, the problems are much worse. The chain moves pretty tightly around the small wheels called derailleur pulleys. A rusted chain with badly moving individual links won’t move through the derailleur easily.
Apart from that, the biggest issue you will encounter is a bad shifting, because the rusty chain in combination with a dirty cassette won’t shift correctly.
How do you get rust off a bike chain?
If a dirty, rusty chain is bad for its lifespan, the obvious solution is to clean it.
There are many ways to clean your chain, with the most effective method using a dedicated chain cleaner tool.
A chain cleaner tool is placed onto the chain. By rotating the crank by hand the chain is moved through three internal brushes and cleaned.
A cheap plastic chain cleaner is about 30 USD. The chain cleaner I use is the Park Tool CM-25. This is a professional cleaner, which is significantly more expensive.
The upside of spending 3 times the amount you would pay for a cheap chain cleaner is that it’s more sustainable, because of the replaceable brushes and aluminum body.
If you don’t have a chain cleaner, or don’t want to buy one, you can use a rag and dishwashing brush. It’s the cheapest method I found for cleaning a chain.
What is the best lubricant for a bike chain?
After you’ve cleaned the chain you have to lubricate it.
Never ride with a non-lubricated chain.
Although this article is not about chain lubricants, I personally use various wax lubricants for all my bikes with a rear derailleur. I’ve written a separate article about reasons for using wax vs lube.
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