Victor said:While swapping out a Shimano XT derailleur from a 2000 model year mountain bike, I noticed that
the pulleys had hardened dirt in the vicinity of the seals. While trying to clean this stuff out
with a toothpick, I noticed that the dirt was trapped in between the pulley and a rubber "seal"
that surrounds the bearing enclosure. The pulleys do not spin freely at all, at least not in the
same manner that I have observed on other of my derailleurs - recent comparisons include a brand
new Shimano 105 and a used Shimano STX. In the past, I have applied a drop or two of Triflow in
the vicinity of the bearing enclosure periodically thinking that this would actually make it to
the enclosed bearing surfaces. Words like "sealed" and "ceramic" appear on the pulley, for further
reference.
My questions, then, are how does one do the following:
1) clean the pulley assembly so that the pulley spins relatively freely on its bearings
2) periodically lubricate the bearings, if this has any meaning for "sealed" bearings.
My understanding of the term sealed is that seals exist, but the bearings are subject to injection
of foreign substances, be they for good or bad.
I do not think you can ever get a useful amount of lubricant in a pulley without dissassembly. And
TriFlo would not be on my list of useful lubricants, either.
In the case of derailleur rollers, most are now shipped dry, devoid of any lubricant whatsoever. You
should open them and add a drop or two of real oil [just about any type] or a smear of grease and
reinstall, taking care to fully tighten the fasteners. If yours have the overdesigned rubber seals,
note the orientation - they won't fit well backwards.
Modern index rollers are different top and bottom. The top assembly floats. In that case the top and
bottom should be opened separately so as not to mix parts. The derailleur cage is cut away at the
top inside. An amazingly high number of consumer disassemblies end up upside down, risking the inner
cage in the spokes and a degradation of shift response.
We notice a distinctive high-pitched whine from dry bushings, in all materials. Pulleys need
lubrication very infrequently, maybe every couple of years, but they do need some. The classic
aluminum cover is plenty sufficient even for wet conditions if you have even a minimal amount of
lubricant.
"Sealed" rollers are harmless but overkill. OTOH in many cases they are half the price of
manufacturer's spares and work as well or better. The Tacx particularly are easy to use, as they
come with sleeves to fit anything under the sun.
Steel-on-steel pulleys exhibit a uniquely bright red rust on opening. Anyone know why? I do not see
that color anywhere else in bicycles.
--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
