Chain guards are a must-have component on bicycles that are ridden primarily for transportation. Chain guards keep clothing from getting caught in the drivetrain, keep grease off of street clothes, and in some cases, protect the chain from the elements. There are three general types of chain guards, each with their respective advantages and disadvantages.
Full Chain Cases
Advantages — Full chain cases completely enclose the chain, front chainring, and rear cog. They fully protect the rider’s clothing from the drivetrain while also offering the major advantage of protecting the drivetrain from rain and road grime.
Disdvantages — Full chain cases are relatively heavy, they’re not compatible with front derailleurs, and some designs can make repairing flats on the roadside difficult. The best insurance against being stranded because of a full chain case is running highly puncture-resistant tires and tubes combined with liquid sealant.
Chain cases are commonly spec’d on European utility bikes, but they’re rarely seen in the U.S. One of the few bikes from a U.S. supplier that comes outfitted with a full chain case is the Breezer Uptown 8 shown in the above photo.
Partial Chain Guards
Advantages — Partial chain guards cover the upper run of the chain from approximately 3 o’clock on the front chainring back to the seat stay. When most people in the U.S. think of a “chain guard”, this is what they’re thinking of. Like full chain cases, partial chain guards protect the rider’s clothing from being soiled or caught in the drivetrain. Partial chain guards typically weigh less than full chain cases and they provide unrestricted access to the rear wheel for roadside repairs.
Disdvantages — Partial chain guards are not compatible with front derailleurs and they don’t protect the drivetrain from the elements.
Advantages — Chainwheel discs are essentially chainrings without teeth that take the place of a second or third chainring on a double or triple crank. They provide a fair amount of protection, they’re lighter than either partial chain guards or full chain cases, and they provide unrestricted access to the rear wheel for roadside repairs. Their greatest advantage is that they allow the use of a front derailleur. The chainwheel disc shown in the photo replaces the third chainring on a triple crank, providing some protection while still enabling shifting between the inner and middle chainrings.
Disdvantages — Chainwheel discs don’t protect the drivetrain from the elements and they only partially protect the rider’s clothing from the drivetrain.