MXA TEAM TESTED: RENTHAL TWINRING SPROCKET

WHAT IS IT? The Renthal Twinring sprocket combines a specially enhanced, 7075 T-6 aluminum-alloy center hub with a long-wearing, high-strength, nickel-coated, steel outer ring.

WHAT’S IT COST? $99.95.

CONTACT? www.renthal.com or (877) 736-8425.

WHAT STANDS OUT? Here’s a list of things that stand out with the Renthal Twinring sprocket.

(1) Production. How does Renthal attach the steel outer ring to the aluminum inner? The outer ring is expanded by being heated and then shrink-fit onto the cooler inner hub. Cold-rolled pins are then used to secure the two parts.

(2) Competition. Renthal cannot lay claim to being the innovator of this idea. It has been tried several times before, most notably by Supersprox, which has been building aluminum/steel hybrid sprockets since 2001. Many Vet riders will also remember the Sidewinder Stealth/Tri-Metal sprockets, which were private-labeled from Supersprox.

(3) Concept. The typical rear sprocket is made from lightweight aluminum but exhibits one major flaw—aluminum wears out quickly. And in the process of wearing out, the soft aluminum teeth engage the chain rollers improperly, stretching the chain. A steel sprocket lasts longer and mates to the chain better, but a solid steel sprocket is heavy—three times heavier than an aluminum sprocket. And that weight is not only unsprung but rotating. The solution (for Supersprox, Sidewinder and Renthal) was simple: bond a ring of durable steel teeth to a lightweight aluminum carrier.

(4) Lifespan. How much longer will a Twinring sprocket last than an aluminum sprocket? Approximately three times longer.

(5) Weight. How much heavier is the Twinring sprocket than a comparable aluminum sprocket? It weighs 12 ounces more than an all-aluminum sprocket and 12 ounces less than an all-steel sprocket.

(6) Price. How much more does a Twinring sprocket cost than an aluminum sprocket? A Renthal Ultralight rear sprocket has a suggested retail price of $69.95, which is $30 cheaper than a Renthal Twinring. But, the extra cost is made up for over time, as the Twinring lasts much longer than an aluminum sprocket.

WHAT’S THE SQUAWK? The two most common squawks are weight and price.