Shimano Mountain Bicycle ATB Rear Derailleurs
SHIMANO XTR / M900 (Not Light Action) REAR DERAILLEUR
The XTR rear is a part of Shimano's eXTRa expensive group of components. The XTR rear derailleur in a way has more in common with the Dura-Ace rear than the XT rear. The XTR has the same even dull cast that the Dura-Ace has only in a Silver color. Both have the pulley cage made of aluminum plates for the front and the back. (Remember the XT uses a steel plate to create the rear most part of the pulley cage.) The XTR group, was the first 8 speed system designed for mountain bikes, this is for use as a 6, 7, or 8 speed rear derailleur and is STI compatible. All the linkages and the pulley cage are made of aluminum to reduce weight. The XTR uses a 5mm allen wrench to mount and fasten the derailleur cable. The cable fastening bolt on both the XT and the Dura-Ace rear use a separate nut that is replaceable for the bolt to fasten to. The link pins fastening the left and right links to the derailleur body, and the mounting bracket/mounting bolt assembly are sealed, (using small recessed plates) against contamination, to reduce friction. The high and low gear cam adjustment screws are on the left side requiring a small Phillips screwdriver for adjustment.
There is also a "B-tension" adjustment screw that moves the entire rear derailleur front to back to add tension to the chain. The XTR also has an adjustment screw for the return spring which adjusts the force used to push the derailleur back from the high to the low geared cog. The convenience adjuster, (this permits you to adjust, without tools, the cable tension as the cable stretches), is easy to grip with a large grey plastic jacket around a steel bolt, with detent at each quarter turn. The guide pulley on the XTR uses a ceramic bushing for the "bearing assembly" that it revolves on. At the core of a nylon-like pulley a white ceramic outer sleeve is pressed into it. Inside this outer sleeve, a greased inner ceramic sleeve slides. The ceramic assembly is surrounded (both front and back) with a rubber gasket that has a stamped aluminum plate in the shape of a cup to shield the guide pulley from dirt contamination. The tension, (or idler pulley), actually has a precision sealed cartridge bearing. This is the first occasion for Shimano, even the Dura-Ace rear doesn't include precision sealed pulley bearings. The pulley cage includes several levels of protection against spoke damage from an overshift. Caution, on the XTR rear, the cable fastening bolt threads into a tapped hole on the body. If you over-tighten this bolt and strip the threaded body there are no replacement provisions, nor is there space for a small after market nut, replacing the derailleur would be necessary. The steel mounting, pivot and pulley bolts can be replaced with SRP Titanium versions and are writen about at the end of this article. Described by Shimano as "middle cage" length, the XTR rear will accept cogs up to 32 teeth in size and is rated at a 33 tooth capacity. It weighs 225.5 grams. Made in Japan.
Price in Catalog
SHIMANO M737 DEORE XT REAR DERAILLEUR
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