THE wheels on bikes haven’t been reinvented  though the chains are getting an update.

Those clinking roller chains that are now standard on most bicycles have long had a drawback known to any cyclist: they become grimy, and can soil a pants leg or a skirt. That’s because the metal links must be oiled regularly, and the oil attracts dirt.

Now companies are developing new designs and materials to replace these chains with grease-free alternatives like polymer cables or belts toughened with carbon fibers.

The Gates Corporation in Denver, a maker of industrial and auto parts, offers belt-driven systems for biking that, unlike chains, require no lubrication, said Frank Scurlock, its global business development manager. The belts, made of polyurethane and shot through with carbon cords to give them tensile strength, have teeth on one side that engage with metal pulleys to turn the belt as the pedals rotate. Other companies offering belt-drive systems for bicycles include Schlumpf Innovations in Vilters, Switzerland, and CycleDrive Systems in Foxborough, Mass.