Shimano derailleur pulleys
Joel Rubinstein
I have a Shimano Deore XT rear derailleur (RD-M739 SGS). The
pulleys are narrower than older Shimano pulleys and use 14 mm
long pulley bolts instead of 16 mm. The guide pulley has
ceramic bearings. That is, a ceramic sleeve is permanently
attached to the plastic pulley, and another ceramic sleeve
slides between the pulley and the pulley bolt. The tension
pulley uses metal sleeves instead.
Problem: The guide pulley ceramic sleeve (the one that comes
free) has cracked into a lot of little pieces.
Questions:
Why does Shimano use ceramic instead of metal?
If I replace the ceramic sleeve with metal, are there any consequences?
If I replace both pulleys with standard wider ones from
another derailleur, is this ok? (I'd have to use the other
derailleur's pulley bolts too.)
What third-party sealed bearing pulleys work with derailleurs
which use 5 mm x 14 mm pulley bolts? Are they any better than Shimano?
Please respond to me directly, as my ISP is sloppy about UseNet posts.
Joel Rubinstein
Sheldon Brown
[posted and mailed]
Joel Rubinstein wrote:
> I have a Shimano Deore XT rear derailleur...The guide pulley has
> ceramic bearings. That is, a ceramic sleeve is permanently
> attached to the plastic pulley, and another ceramic sleeve
> slides between the pulley and the pulley bolt. The tension
> pulley uses metal sleeves instead.
>
> Why does Shimano use ceramic instead of metal?
The ceramic is longer wearing. They use metal on the tension (lower)
pulley because a bit of slop in the tension pulley will not have any
effect on shifting.
> If I replace the ceramic sleeve with metal, are there any
> consequences?
It won't last as long. The cheaper models of Shimano derailers use
metal bushings on both pulleys, only the fancier ones use the ceramic
bushing.
> If I replace both pulleys with standard wider ones from
> another derailleur, is this ok?
Sure. Many derailer pulleys that look similar are actually specific to
their position. Typically, if one pulley has wide, blunt "teeth" and
the other has beveled "teeth", the blunt one goes on top, where it can
guide the chain more precisely into position, while the beveled one goes
down below, where it is better able to handle chain misalignment, as
when using the "criss-cross" gears.
> What third-party sealed bearing pulleys work with derailleurs
> which use 5 mm x 14 mm pulley bolts? Are they any better than Shimano?
All third-party pullieys work with Shimano derailers. I like the ball
bearings, but some people prefer the Shimano jockey (upper) pulleys
because of their "Centeron" (floating) design, which may make them
slightly more forgiving of mis-adjustment.
Sheldon "Jockeying For A Tension" Brown
Newtonville, Massachusetts
+-----------------------------------------------------+
| Always be sincere, even when you don't mean it. |
| --Irene Peter |
+-----------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-1040 FAX 617-244-1041
http://www.sheldonbrown.com/harris
Bike Doc
Sheldon I have found the ceramic pulley's do not last longer. I have
had three Shimano
ceramic pulley bushings of mine that have cracked, two Durace, one XTR.
Riders should check these bushings on a regular basis for cracks.
I have since replaced these with non-ceramic pulleys for this reason.
--
Neither cold, rain, snow or dark of night will keep
a serious rider off their bike. Ride on !!!
Bike Doc
*************************************************************
To reply by e-mail remove {NOSPAM} from address.
Absolutely no advertisements, junk mail, spam, etc..
Opinions in news groups are for entertainment
purposes only.
*************************************************************
Sheldon Brown wrote in message <34B24A24...@sheldonbrown.com>...
Pechs1
When i asked Wayne Stetina about the pulleys he suggested that I take any
pulley w/ a ceramic insert and take apart and lube when new w/ a little grease
and throw away the draggy little rubber seals and the pulleys will last
longer-i have seen many ceramic inserts 'dissolve into dust'-poor design-
The new 9 speed ones are much better altho directional-not only top and bottom
but also left/right BUT....D-A and Ultegra are different-very
'shimano'
Pietro
John Everett
In article <34B24A24...@sheldonbrown.com>, Capt...@sheldonbrown.com
says...
>
>All third-party pullieys work with Shimano derailers. I like the ball
>bearings, but some people prefer the Shimano jockey (upper) pulleys
>because of their "Centeron" (floating) design, which may make them
>slightly more forgiving of mis-adjustment.
I don't know about all replacement pulleys, but Bebop Disk Jockeys also have
a floating jockey wheel design. Although the design is significantly
different from the Shimano, it accomplishes the same thing; slight side to
side freedom of movement.
--
jeve...@wwa.DEFEAT.UCE.BOTS.com (John Everett) http://www.wwa.com/~jeverett
^^^^^^^^^^^^^^^
Things have gotten so bad I feel the need to disguise my email address.
And I don't like this explanation because I just hate long signatures.
Chris Neary
jeve...@wwa.DEFEAT.UCE.BOTS.com (John Everett) wrote:
>
>I don't know about all replacement pulleys, but Bebop Disk Jockeys also have
>a floating jockey wheel design. Although the design is significantly
>different from the Shimano, it accomplishes the same thing; slight side to
>side freedom of movement.
So do the Gorilla Billet pulleys.
Chris Neary
dia...@aimnet.com
"It doesn't get any easier - you just go faster" - Greg Lemond
nbce...@delphi.com
"Bike Doc" <gzaid{NOSPAM}@chicagonet.net> writes:
>Sheldon I have found the ceramic pulley's do not last longer. I have
>had three Shimano
>ceramic pulley bushings of mine that have cracked, two Durace, one XTR.
>Riders should check these bushings on a regular basis for cracks.
>
>I have since replaced these with non-ceramic pulleys for this reason.
did not have a service life anywhere near what I have come to expect from
other brands such as Campy. I replaced them with TNT sealed bearing pulley
units....very nice! Lets hope these last.
Brian Lafferty
Propeloton
I too have seen a lot of ceramic pulleys disappear into dust-poor design but
probably cheaper to produce.
Peter
ProPeloton
nbce...@delphi.com
went bad were DA circa 1990 or 91 with only 8 to 10 thousand miles.
Brian Lafferty
Propeloton
Some of their ders. still have the ceramic crap but D-A , Ultegra, XTR all have
very unique to each model sealed pulleys-not only top and bottom models but
lalso directional...I don't think these 'engineers' at shimaNO could have made
it more diffucult if they tried.....FWIW-I got a Nexus hub to build a wheel for
a friend-not assembled-w/ a little plastic bag full of an odd assortment of
spacers, notched things, little painted things....those same engineers are
probably getting a real yuck when us lowly american mechanics try to put their
stuff together......
Peter'would rather walk than use shimaNO' at propeloton