The first round of the World Cup series in Pietermaritzburg, South Africa, is likely going to be ground zero for a number of new, prototype bikes and parts that will be put to the test under the world's best riders. Included on that list is Trek World Racing's Aaron Gwin, who's Session 9.9 race bike was observed sporting what is clearly a prototype Shimano rear derailleur. Gwin ran away with last year's World Cup overall, taking a record five wins in the process, but besides being incredibly fast and consistent he is also known for providing great feedback about the gear he is using. He was one of the few riders last season who was making use of Shimano's prototype Saint brake calipers, so it made sense when PB photographer Fraser Britton spotted what looks to be a prototype 2013 Saint rear derailleur bolted to his bike. Our questions to Shimano went unanswered, but there is plenty to be learned from the photo below.
Aaron Gwin's Trek Session 9.9 had this prototype Shimano derailleur, likely a 2013 ten speed Saint unit in testing, attached to it. A Shadow+ friction clutch is hidden underneath the black cover that adds a considerable amount of tension to the derailleur's cage pivot, thereby increasing chain's tautness.
The prototype unit, with its handmade and unfinished appearance, clearly stands out from the current model year Saint derailleur's black and gold colours, but it doesn't take a magnifying glass to see that there is much more going on here. Spot that black cover held in place with three screws directly over where you would normally expect to see the main cage pivot? The not-so-mysterious cover is hiding the derailleur's friction clutch, likely a very similar unit to what is found on the current XTR derailleur, as well as on the upcoming 2013 XT and SLX models. That much is for certain, but what does come as a surprise is the prototype's complete lack of a 'clutch lever' (the anodized gold switch on the Shadow+ XTR derailleur
) that would allow the friction mode to be engaged and disengaged. This begins to make more sense when you consider that quick wheel changes, a job that would benefit from disengaging the derailleur's clutch, won't overly concern the majority of downhillers. The prototype derailleur's clutch is still likely to employ an adjustment feature, though, via an internal friction nut that is turned to alter the cage's resistance.Pinkbike's Take:
|So how does the Shadow+ friction clutch work, and why it make sense on a downhill bike? The clutch provides friction in only one direction so the pulley cage can't swing forward until a shift overcomes the clutch pressure - that keeps the chain from becoming slack between the derailleur and the chain ring. This is said to work wonders for keeping chain noise down, as well as lessening the chance of losing a chain over rough trails, on bikes that use a front derailleur, and that may have excess chain slack in certain gear combinations, but it could also make sense on downhill bikes due to their long travel suspension and the speed at which they can cover ground. Chain retention is a fairly dialled art these days, with riders rarely losing a chain with the proper setup, but the added tension provided by the Shadow+ clutch will likely lower the chances of it occurring to close to zero. - Mike Levy|