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Spotted: Prototype SRAM cyclocross single chainring

SRAM appears to be testing a cyclocross-oriented single chainring that does not require a chain watcher or tensioner — and the move could be indicative of big things to come for the Chicago-based manufacturer. Ryan Trebon (Cannondale-Cyclocrossworld.com) competed at the Trek U.S. Gran Prix Deschutes Brewery Cup earlier this month on a 1×10 drivetrain similar to the XX1 1×11 mountain group.

The Cannondale-Cyclocrossworld.com team has a history of testing and debuting SRAM cyclocross components. Tim Johnson rode the Chicago-based manufacturer’s Avid BB7 disc brakes to a win at Jingle Cross Rock in November 2011 and earlier this month debuted the new HydroR disc brakes at CXLA.

At the Bend, Oregon, stop of the USGP, Trebon was aboard his typical lime green Cannondale Super X disc bike, but instead of the standard 46-39 chainrings, he ran a single front chainring without any type of chain watcher. That he was running a single ring is of no great interest in itself; but running a single without a chain watcher requires some alterations to the rear derailleur, chainring, or chain to ensure that the chain won’t pop off.

Oddly, the rear derailleur on Trebon’s bike appeared to be a standard Red 2012 rear derailleur, still with 10 speeds, and does not have a clutch mechanism to limit chain slack like in SRAM’s XO Type 2 rear derailleur — so that option for secure chain retention is off the table. It is possible that Trebon’s Cannondale mechanic Dusty Labarr retrofit a stronger spring to the Red derailleur to keep chain slack taught. When asked, Labarr said he could “neither confirm nor deny any derailleur retrofitting.”

With no chain watcher and, at least to the naked eye, no alterations to the rear derailleur, the only remaining method of chain retention falls with the chainring itself.

Trebon’s chainring teeth look similar to those of SRAM’s XX1 crankset, which, thanks to its extra tall teeth and special chain, does not require a chain watcher to keep the chain on the rings. Even if the Cannondale mechanics did perform some modification to the rear derailleur, Trebon would likely want the added insurance this tooth profile provides. When asked whether Trebon was running an XX1-style front chainring married to his Red drivetrain, SRAM’s Michael Zellmann also said he “can neither confirm nor deny that.”

The mystery chainring appears to be in the early stages of development. The look is unfinished, still a raw silver aluminum color that doesn’t match the rest of Trebon’s Red drivetrain.

The ring indicates potential changes to the way SRAM looks at its ’cross, and possibly even road, groupsets. If SRAM’s next ’cross group were to be modeled after the mountain XX1 group, and this ring is a persuasive clue that it might be, then we would expect a move to a wide range cassette and 11 rear cogs just like XX1, which uses an 11-speed 10-42 cassette mounted to a special freehub. With the move towards 135mm rear spacing on disc ’cross bikes, SRAM may even try to pack in 12 cogs out back.

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