Shimano HG (Hyperglide) chains The chain transfers the force from the chain ring to the sprocket of the rear hub. It's exposed to extreme loads and weather conditions. Chains vary in length depending on the conditions of use, but each must be replaced sooner or later. Replacing the chain in time is the only way to protect the chainrings and sprockets from excessive wear. To get the best possible performance from the Shimano HyperDrive system, it's important to use original Shimano HG chains.