Race Face has developed a new Era chainring that is said to be the first of its kind. Chainrings can be into three parts, the teeth crank interface, and the spider. These all have specific demands on materials, to create the best chainring possible Race Face has used multiple materials when designing the Era chainring.
Steel is hard-wearing but adds a lot of weight, alloy is durable but would wear quickly, and carbon, well carbon has a time and a place, and areas of high wear are not one of those.
