Shimano Road Rear Derailleurs


The lightest Shimano rear derailleur at 207.5 grams. It is SIS compatible using the Double Servo-Panta Mechanism and can be used in a 6, 7, or 8 speed shifting system. This changer is made of aluminum where ever possible. Only the mounting and pivot bolts holding it together and the pivot points are made of steel. Shimano has made efforts to seal all the points of dirt contamination including; sealed link pivots (the four stainless steel pins that the body revolves on) using tiny flanges, sealed pulleys achieved by using interlocking seals surrounded by a rubber o-ring, and a sealed axle bracket (the threaded bolt and housing that fasten the derailleur to the frame dropout) using an o-ring seal. The guide pulley has an aluminum outer wheel that the chain runs around increasing it's life over the standard plastic pulleys. The pulleys use interlocking seals to seal them against contaminates,

and where the bolt holding the pulley in the cage passes through the pulley, there is a small ceramic bushing that revolves inside a larger ceramic bushing sleeve to reduce friction. This ceramic bushing arrangement is Shimano's alternative to using precision sealed bearing cartridges to reduce friction, but lets remember that engineers continue to talk about making car engines out of ceramics because they are lightweight and have reduced friction over steel to steel construction. The cage is constructed with a chain retainer to prevent the chain from being removed accidentally and the front facing edges of the cage have been rolled to prevent them from catching spokes in the event of an overshift. Included in the adjustments you can make are; the return spring force, high and low gear, B-Tension adjustment and there is a convenience adjuster to take up cable slack. The steel mounting, pivot and pulley bolts can be replaced with SRP Titanium versions and are writen about at the end of this article. A 5mm hex wrench installs and cinches the cable. The Dura-Ace rear changer will accept a maximum rear cog of 26 teeth and a minimum rear cog of 12 teeth. The greatest difference in size between the two front chainwheels can't exceed 14 teeth and the Total Capacity for this derailleur is 26 teeth.
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