More about Length
Most of the chains sold today are in stock length. It means they are sufficient for the majority of bike applications. The correct number of links has to be taken out before any installation is done. This is required for the drive train to work without a hitch. There is a pin joining the links. A chain utility can be used to push these. This is necessary when the links have to be shortened or new ones added.
With derailleur gears, the chain will be quite lengthy. In fact they can be shifted to the biggest chain ring up front. They can also be placed on the biggest rear sprocket with no jamming. The length can be adjusted.
When the ring is moved from the smallest rear sprocket and smallest front chain ring, the back derailleur cannot take the remaining slack up. These requirements can only be met if the derailleur at the rear works with the paraphernalia used for the bicycle. This will be apparent when you study a bike chain size chart.
Single Speed Bikes
The situation is different with these bikes and hub gears. Here the chain has to correspond with the distance between the rear hub and crank. It must also match the rear sprocket and front chain ring sizes. These bicycles usually come with a device for making minute modifications. These usually include track ends and horizontal dropouts. Other bikes have unique mechanisms at the bottom bracket or rear hub. In some cases, a chain half-link is required.
A bike chain is used for transmitting the power from the pedals on the bike drive wheel. This action propels the bike. The majority of chains are built of alloy steel or plain carbon. However, there are now some chains with nickel-plating. This feature is usually used for aesthetic reasons. But it can also serve to prevent rust. The presence of nickel also gives it some amount of self-lubrication.
If you are studying a bike chain size chart, remember to check the efficiency. A well made chain can have a proficiency level of over 98%. However, lubrication will not be a factor. The best drive performance comes from big sprockets.