What features should I look for in a chain?

Question

I have noticed there are many manufacturers of chains and most have several different chains of varying cost in their lineup. How to select a chain from the huge amount of available chains?

Answer 1

The choice of chain is first of all determined by the type of drivetrain. For instance, a 11-speed derailleur requires an 11-speed chain. A bike with a single ring and single cog, fore and aft, respectively, requires either a wide 1/8" or narrow single speed chain.

If one is entirely overwhelmed by the choice of chains one cannot go wrong with taking a chain of the same manufacturer as their cassette (cluster of sprockets). For example, a Shimano road chain for Shimano equipped road bike.

Most manufacturers have different series of chains. In general the more expensive chains wear not as fast. This usually comes with reduced drivetrain losses. There may be exceptions to this generalisation, which can be found in tests.

For most gear options chains between the large manufacturers are interchangeable. At the moment these are Wippermann, Shimano, SRAM, and KMC. (An exception are 12 gear drivetrains where chain standards are proprietary.) There are quality and price differences between brands. Again, tests will help to determine the best option.

How long a chain lasts and how large drivetrain losses are predominantly determined by right lubrication. This is an enormous topic though: it changes widely between use-cases and weather conditions. (This entails also a massive lack of hard evidence and a thus fierce debates.)

As far as I know there are no significant differences in chain reliability between brands. Chain failures in well maintained and unworn chains are too rare to get enough test data in controlled tests.

tl;dr: When narrowed down the choice of chain to what works with a given bike one may choose a chain that is a compromise of costs and longevity.

Answer 2

There are two types of chains available for bicycles: bushing-type chains and bushingless chains. Bushing-type chains consist of five parts: outer links, inner links, pins, bushings and rollers. The bushingless chain remove the bushing from the parts (thus leaving only 4 parts) and replace the bushing by two half-bushings stamped into the inner links. Because the bushingless chain has 4 parts as opposed to 5, it is cheaper.

The bushing-type chain is more durable if properly taking care of the chain. Proper care means that you lubricate the chain only when necessary as lubrication has risk of carrying dirt into the innards of the chain, and clean the chain thoroughly before every lubrication event. The reason for the better durability is that bushing prevents dirt from getting inside the chain where it can do damage, and does a better job of retaining the lubricant inside the chain.

In contrast to the bushing-type chain that is more durable, the bushingless chain is stronger. So, if you are a heavy 120 kg rider riding an electric MTB with 22-tooth small chainring and clipless pedals, the combined pedaling and electric assist forces can cause very great tension in the chain through the small chainring. A bushing-type chain may not withstand this high chain tension. Also combine the fact that many bicyclists shift under load which the bushingless chain is better at withstanding, and you see why bushingless chain is predominant today.

The bushingless chain is so predominant that one cannot find bushing-type chains for derailleur geared bicycles anymore. This is rather unfortunate, as chain life with proper chain care has decreased due to bushingless chains.

After noticing that the manufacturers have already made the choice for the chain type and you cannot make the choice yourself (i.e. you must buy bushingless), the second choice is speed count. After 5/6/7/8 speed chains, which were the same size (except 7/8 speeds have shorter pin protrusion past the plates), each generation of speed count nowadays comes with new chain dimensions. The speed count must be chosen based on the number of rear sprockets. Higher speed counts have narrower chains. You might think they are therefore less durable, but actually the converse is true: improved manufacturing and materials make them more durable, but at a far greater cost.

Single speed or internally geared bicycles may use a wider 1/8" chain as opposed to the approximately 3/32" wide chain used by derailleur bicycles. However, there are single speed and internally geared bicycles using a derailleur bicycle chain as well.

After deciding what speed count to get, you must decide on proper chain length. This depends on the front and rear tooth counts for the biggest sprocket and chainring, and the chainstay length. Calculators are available. At least for Shimano, the longest cheap chain length is 116 links and in most cases you should select this, as chains can easily be shortened but lengthening a chain is tricky and requires purchase of two chains. It is unfortunate that today many bicycles are sold with excessively short chainstays, resulting in most sold chains being very short, so a long chainstay bicycle such as a touring bicycle might not have a normally priced chain available and must thus use the very expensive 138-link chain.

The most important part of the chain is the chain pin, as it is the part wearing the most. Unfortunately, information about the material quality of the pin is not easily available, so most people buying a chain cannot reasonably compare the quality of pins in two chains of different prices. Ideally the pins would be chrome hardened. Information about the presence or absence of a hardening process is very hard to obtain, but most name brand chains should have hardened pins.

An important consideration for chains is how to repair them with roadside emergency tools during a trip if a chain fails. Carrying a mini chaintool in the emergency tool kit is very useful. Ideally, chains would have reusable pins. However, the proliferation of shifting under load and the need to have very short pin protrusion past the side plates due to the ridiculously huge sprocket counts in modern bicycles has demanded chain makers to "punch" the pins for extra positive retention strength in a manner that makes them not reusable. They can be driven out, but not driven back in.

There are two approaches for allowing a chain with "punched" pins to be (re)connected:

• Reinforced connecting pin (used by Shimano)
• Quick link (used by many non-Shimano manufacturers such as SRAM and KMC)

The quick link chains are sold to buyers wanting reusability and tool-free disconnection, but fail to provide tool-free disconnection of the two. They have a number of drawbacks:

• A single quick link is more expensive than a single reinforced connecting pin, and the emergency tool kit should have several of the chosen connecting device to allow repairing many failures
• A single quick link is heavier than a single reinforced connecting pin, and the emergency tool kit should have several of the chosen connecting device to allow repairing many failures
• It is practically impossible to disconnect a quick link by hands in a dirty chain. When the chain is clean, it is possible, but dirt gets into the quick link mechanism necessitating either cleaning the chain or using pliers.

The only benefit of quick links is that they can be reused, but as they have pins that wear, ideally a new quick link is used for a new chain. Reinforced connecting pins are for single use only.

In theory, the reinforced connecting pin is a more secure connecting mechanism, but in practice we aren't seeing quick links snapping open en masse.

Most of the differences in various N-speed chains by a manufacturer are whether the chain is asymmetric / directional (more expensive but shifts better) and what cosmetic look the chain has. Even the cheapest chains today shift well enough for most purposes, so it may not make sense to pay the great recurring cost of an asymmetric / directional chain for such a fast-wearing part. Of the cosmetic finishes, some may prevent the outside parts of the chain from rusting. Cosmetic external rust in a chain is of no durability concern and an externally rusted chain works as well as a rust-free chain. Besides, this matters only if the bicycle is left in the rain for extended periods. Thus, the cheapest cosmetic finish is preferrable. It's in the inside where it matters, and if a chain is lubricated and left standing in the rain, the inside parts of the chain won't rust.