Updated: SRAM to launch clutch style rear mech

By James Huang, tech editor, in Boulder, USA | Thursday, January 26, 2012 10.00am

After SRAM posted a 'spy shot' on their Facebook page with the caption "can you spot anything interesting?" we set our intrepid technical editor James Huang off to do some digging, and he found that SRAM are, in fact, quite close to launching their own clutch equipped rear derailleur.

The visual differences are subtle but the P-knuckle and pulley cage are clearly different. SRAM aren't revealing much detail but have all-but-explicitly confirmed to BikeRadar that it's a new clutch-equipped rear derailleur, similar in concept to Shimano's heralded XTR Shadow Plus design.

"It's a new prototype – well, it's obviously a little more than a prototype," SRAM drivetrain product manager Chris Hilton told BikeRadar. "It's certainly not the end of what that product will be. There are some things that are missing but it's something that will be available this model year. When guys start building high-end bikes, that's when it'll be available."

SRAM's prototype (left) looks markedly different from the current x0 mech (right): sram's prototype (left) looks markedly different from the current x0 mech (right)

SRAM's prototype (left) looks markedly different from the current X0 mech (right) in the p-knuckle area

The derailleur's finished look suggests it's not far off from production, and Hilton says it's already undergone a lot of field testing. In fact, he raced an earlier version at the Finale Ligura Super Enduro this past October and there have been "significant improvements" made since then.

Technical information regarding exactly how SRAM are controlling the pulley cage movement isn't yet available – Shimano use an adjustable steel band lined with friction material and clamped around the pulley cage pivot – but the company did send us a few blurry images that at least reveal how the system will be turned on and off. 

While Shimano opt for a little lever, SRAM use a simple push button, marked with the familiar padlock icon borrowed from RockShox. Weight and cost specifics haven't yet been released, but we expect modest jumps in both categories as compared to a standard X0 unit.

Users will be able to engage and disengage the pulley cage clutch with this push-button switch. the image is intentionally blurry so we unfortunately can't make out the text at top right:

Users will be able to engage and disengage the pulley cage clutch with this push-button switch. The image is intentionally blurry so we can't make out the text at bottom left

New brake on the way, too?

Also spotted in the background of Hilton's bike is an as-yet-unannounced four-piston Avid hydraulic disc brake caliper – either a successor to the current Code or a more powerful variant of the company's versatile Elixir range. As compared to a conventional two-piston setup, four smaller pistons would theoretically allow for more carefully tuneable pressure distribution on the pad backings along with more efficient heat transfer from pad to caliper for improved cooling.

We have no information from SRAM regarding this development but the image  confirms details that include a two-piece caliper design (long said by SRAM to be stiffer than one-piece bodies due to the steel bolts), top-loading pads, a rotating banjo with stainless steel fittings and, curiously, direct post mount type mounting with no trademark CPS gimbaled washers in sight.

Also spotted in the image are new four-piston brake calipers from avid:

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Also spotted in the image is a new four-piston brake caliper from Avid

Stay tuned for more information but we expect to receive full details no later than the Sea Otter Classic, held 19-22 April.

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