Lubricating the bearings of Ivy's 1997 Shimano RD-M950-GS pulleys. The seals do a good job, keeping degreaser and gunk out through countless miles and chain cleanings. Still, since the seals are out, I decided to remove the old, stock grease, and replace it with premium grease from Finish Line. A grease gun makes the operation easier.
The bearings in the G-pulley are tiny, about 1.6 mm (a little under 63-thousandths of an inch) in diameter. If it drops out of its Delrin™ cage on the floor (or down the sink), you are up the creek without a paddle.
The G-pulley, short for the "Guide Pulley," is located closest to the cassette / gear cluster / cogs. Part of the Centeron™ mechanism, it is designed with some axial float (sideway "play") to compensate for imprecise derailleur adjustment.
The T-pulley, short for the "Tension Pulley," is mounted at the end of the derailleur cage. It has no axial float.
Flipping the pulleys over to reverse their general direction of operation slightly prolongs their life.
Weightweenies — and/or those with deep pockets — may wish to switch to pulleys with ceramic ball bearings. The ball bearings are supposedly 60% lighter than regular steel bearings.
More pointers found here: Pulley TLC II.
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