How important is the sleeve?

Just got a Shimano XT 760 crankset that came installed on the frame.
Unfortunately, the installer dicked up the plastic sleeve that runs between
through the BB shell between the two cups, crushing it toward one end and
cracking it, thereby negating whatever seal it was intended to provide.
Anyone know how important this sleeve is to the longevity of the bearings in
the cups? I can't find anyone selling the sleeve separately, so I'm
guessing it may not be all that significant.

Cal

"CEarly" wrote:

Just got a Shimano XT 760 crankset that came installed on the frame.
Unfortunately, the installer dicked up the plastic sleeve that runs between
through the BB shell between the two cups, crushing it toward one end and
cracking it, thereby negating whatever seal it was intended to provide.
Anyone know how important this sleeve is to the longevity of the bearings in
the cups? I can't find anyone selling the sleeve separately, so I'm
guessing it may not be all that significant.

Cal


Your guess is correct, in my opinion. Any sealing provided by those
sleeves is only effective for chunks of dirt, twigs and small birds.
Such things can get into well ventilated BB shells, those on fancy bikes
with a lot of metal carving in the area. The real problem with those
"seals" is water which enters and then doesn't leave, which is the
rationale for well-ventilated BBs.

--
Ted Bennett

CEarly wrote:
Just got a Shimano XT 760 crankset that came installed on the frame.
Unfortunately, the installer dicked up the plastic sleeve that runs between
through the BB shell between the two cups, crushing it toward one end and
cracking it, thereby negating whatever seal it was intended to provide.
Anyone know how important this sleeve is to the longevity of the bearings in
the cups? I can't find anyone selling the sleeve separately, so I'm
guessing it may not be all that significant.

Cal

VERY important to keeping the bearings happy. The person that installed
one owes you a sleeve...

Just out of curiosity, where do you derive this information? I could
find no reference to it anywhere from Shimano. I figure, if they don't
think it's important enough to mention, it must not be critical.

Oh, could you elaborate on the "VERY important" nature?

Thanks,
Robin

Robin Hubert wrote:

Just out of curiosity, where do you derive this information? I could
find no reference to it anywhere from Shimano. I figure, if they don't
think it's important enough to mention, it must not be critical.

Oh, could you elaborate on the "VERY important" nature?

If this is the conventional type, it keeps the cups apart and prevents
you from destroying the bearings with huge side loads when installing
the unit. If the new "outside" type, I have no idea.

"Zog The Undeniable" wrote in message
news:43666bca.0@entanet...
Robin Hubert wrote:

Just out of curiosity, where do you derive this information? I could
find no reference to it anywhere from Shimano. I figure, if they don't
think it's important enough to mention, it must not be critical.

Oh, could you elaborate on the "VERY important" nature?

If this is the conventional type, it keeps the cups apart and prevents you
from destroying the bearings with huge side loads when installing the
unit. If the new "outside" type, I have no idea.

Nah, it's a piece of plastic and could never resist any significant force.
This kind of "BB" consists of two separate "cups" that hold the cartridge
bearings for the pipe spindle, 2-piece crank to run on. The cups seat
against the outside of the BB shell. The plastic sleeve has O-rings that
seal against the inner surfaces of the cups. There's no rotation involved
between the cups and the sleeve, so I'm presuming it could provide a pretty
effective seal against water getting into the bearings after coming in via
the seat tube or elsewhere. BTW, the frame doesn't have a hole on the
bottom of the BB shell, so I guess the frame manufacturer is extremely
confident that water will never get in there, but that hasn't been my
experience with many different frames over many years. So, I'll rev up my
trusty drill and make one where it should be. Of course, this voids the
warranty, blah, blah, blah. BTW, I've never heard a good argument for why a
BB shell shouldn't have a hole in the bottom of it for water to get out.
Anyone who's a no-hole-in-the-BB-shell believer want to try to convert me?
I'd be interested in hearing why anyone thinks there shouldn't be a hole
there.

Cal

CEarly wrote:
"Zog The Undeniable" wrote in message
news:43666bca.0@entanet...
Robin Hubert wrote:

Just out of curiosity, where do you derive this information? I
could find no reference to it anywhere from Shimano. I figure, if
they don't think it's important enough to mention, it must not be
critical. Oh, could you elaborate on the "VERY important" nature?

If this is the conventional type, it keeps the cups apart and
prevents you from destroying the bearings with huge side loads when
installing the unit. If the new "outside" type, I have no idea.

Nah, it's a piece of plastic and could never resist any significant
force. This kind of "BB" consists of two separate "cups" that hold
the cartridge bearings for the pipe spindle, 2-piece crank to run on.
The cups seat against the outside of the BB shell. The plastic
sleeve has O-rings that seal against the inner surfaces of the cups.

You answered your question right there.

There's no rotation involved between the cups and the sleeve, so I'm
presuming it could provide a pretty effective seal against water
getting into the bearings after coming in via the seat tube or
elsewhere. BTW, the frame doesn't have a hole on the bottom of the
BB shell, so I guess the frame manufacturer is extremely confident
that water will never get in there, but that hasn't been my
experience with many different frames over many years. So, I'll rev
up my trusty drill and make one where it should be. Of course, this
voids the warranty, blah, blah, blah. BTW, I've never heard a good
argument for why a BB shell shouldn't have a hole in the bottom of it
for water to get out. Anyone who's a no-hole-in-the-BB-shell believer
want to try to convert me? I'd be interested in hearing why anyone
thinks there shouldn't be a hole there.

You answered your question right there. The bottom of the BB shell has very
little stress on it. Someone had a link to BB shells that were nicely
sculpted out in the frame maker's name. A whole lot of material had been
taken out of some of them.

--
Phil, Squid-in-Training

Robin Hubert wrote:
Just out of curiosity, where do you derive this information? I could
find no reference to it anywhere from Shimano. I figure, if they don't
think it's important enough to mention, it must not be critical.

Oh, could you elaborate on the "VERY important" nature?

Thanks,
Robin

By looking at the design. I don't often look to shimano for anything of
importance. Water will go into the back of the bearing w/o the sleeve,
just like it did on a cup and ball BB, w/o the little crud guard.

With the sleeve, it won't, pretty simple actually.

"Qui si parla Campagnolo" wrote in message
oups.com...

Robin Hubert wrote:
Just out of curiosity, where do you derive this information? I could
find no reference to it anywhere from Shimano. I figure, if they don't
think it's important enough to mention, it must not be critical.

Oh, could you elaborate on the "VERY important" nature?

Thanks,
Robin

By looking at the design. I don't often look to shimano for anything of
importance. Water will go into the back of the bearing w/o the sleeve,
just like it did on a cup and ball BB, w/o the little crud guard.

With the sleeve, it won't, pretty simple actually.


That's how it looks to me, too.

Cal