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ceramic bearings



 
 
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  #1  
Old April 10th 08, 06:04 AM posted to rec.bicycles.tech
Rick Roof[_2_]
external usenet poster
 
Posts: 2
Default ceramic bearings

Just installed ceramic bearings in my front wheel. The original
bearings seem much smoother. Is this just because the ceramics are
not broke in? They just don't seem as smooth as the bearings I took
out. I ended up putting the originals back in for now. Any info
would be appreciated. Thanks.

Rick

"We don't slow down because we get old. We get old because we slow
down."

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  #2  
Old April 10th 08, 06:25 AM posted to rec.bicycles.tech
Dave Mayer
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Posts: 97
Default ceramic bearings


"Rick Roof" wrote in message
...
Just installed ceramic bearings in my front wheel. The original
bearings seem much smoother. Is this just because the ceramics are
not broke in?


If there was a difference in 'smoothness' between steel and ceramic
bearings, it would be so infintesimal so as to be immesurable with real
equipment. Difference in watts power usage on the bike?? Basically zero.
Aerodynamics is many orders of magnitude more important.

The only possible positive of ceramics is that they may survive a little
longer in a hub that is contaminated with grit and water. Maybe.

But this brings up the bigger question as to why not just appropriately
maintain your hubs? An even better solution would be to get a hub that has
a grease injection port. Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.



  #3  
Old April 10th 08, 07:41 AM posted to rec.bicycles.tech
Lou Holtman
external usenet poster
 
Posts: 86
Default ceramic bearings


"Dave Mayer" wrote in message
news:rxhLj.168159$pM4.160323@pd7urf1no...

"Rick Roof" wrote in message
...
Just installed ceramic bearings in my front wheel. The original
bearings seem much smoother. Is this just because the ceramics are
not broke in?


If there was a difference in 'smoothness' between steel and ceramic
bearings, it would be so infintesimal so as to be immesurable with real
equipment. Difference in watts power usage on the bike?? Basically zero.
Aerodynamics is many orders of magnitude more important.

The only possible positive of ceramics is that they may survive a little
longer in a hub that is contaminated with grit and water. Maybe.

But this brings up the bigger question as to why not just appropriately
maintain your hubs?


Agreed

An even better solution would be to get a hub that has
a grease injection port.


That is the second stupiest way to maintain a hub. The first is not to
maintain the hub at all. You have to inject a ton of grease to push out the
old dirty grease through the seal. Not very healthy for the seal. Choose a
hub that is easy (take apart and adjust afterwards) to maintain. Then you
maintain it more often. I vote for Campy hubs.

Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.


Lou


  #4  
Old April 10th 08, 07:54 AM posted to rec.bicycles.tech
Dre[_2_]
external usenet poster
 
Posts: 13
Default ceramic bearings

"Lou Holtman" wrote in message
...

"Dave Mayer" wrote in message
news:rxhLj.168159$pM4.160323@pd7urf1no...

"Rick Roof" wrote in message
...
Just installed ceramic bearings in my front wheel. The original
bearings seem much smoother. Is this just because the ceramics are
not broke in?


If there was a difference in 'smoothness' between steel and ceramic
bearings, it would be so infintesimal so as to be immesurable with real
equipment. Difference in watts power usage on the bike?? Basically
zero.
Aerodynamics is many orders of magnitude more important.

The only possible positive of ceramics is that they may survive a little
longer in a hub that is contaminated with grit and water. Maybe.

But this brings up the bigger question as to why not just appropriately
maintain your hubs?


Agreed

An even better solution would be to get a hub that has
a grease injection port.


That is the second stupiest way to maintain a hub. The first is not to
maintain the hub at all. You have to inject a ton of grease to push out
the
old dirty grease through the seal. Not very healthy for the seal. Choose a
hub that is easy (take apart and adjust afterwards) to maintain. Then you
maintain it more often. I vote for Campy hubs.

Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.


Lou


I vote for sealed bearing hubs, ie, no maintenance You just ride until
they **** themselves, then replace. I haven't had to replace one yet and I
have a couple of hubs that have had an absolute kaning (in the mud and
water).

I cant wait till the XT hubs on my SS die so I can replace them with some
nice DT's, then I never ever have to worry about those stupid shimano
setups, such a pain to set, especially when I have to replace *yet* another
busted freewheel assembly

Cheers Dre (talking about mtb hubs here though)


  #5  
Old April 10th 08, 08:08 AM posted to rec.bicycles.tech
Werehatrack
external usenet poster
 
Posts: 1,416
Default ceramic bearings

On Thu, 10 Apr 2008 05:25:43 GMT, "Dave Mayer"
may have said:

But this brings up the bigger question as to why not just appropriately
maintain your hubs? An even better solution would be to get a hub that has
a grease injection port. Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.


Too much grease increases drag, at least until enough is forced back
out for the grease packs to shear and develop gaps. The amount that
would be present after pumping in enough to actually repack the
bearings would be in that range easily.

Pumping in more grease also does not remove the contaminated grease
that's already present.

Proper maintenance begins with "Clean".

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.
  #6  
Old April 11th 08, 08:08 AM posted to rec.bicycles.tech
Ryan Cousineau
external usenet poster
 
Posts: 4,044
Default ceramic bearings

In article ,
Werehatrack wrote:

On Thu, 10 Apr 2008 05:25:43 GMT, "Dave Mayer"
may have said:

But this brings up the bigger question as to why not just appropriately
maintain your hubs? An even better solution would be to get a hub that has
a grease injection port. Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.


Too much grease increases drag, at least until enough is forced back
out for the grease packs to shear and develop gaps. The amount that
would be present after pumping in enough to actually repack the
bearings would be in that range easily.


If you can demonstrate it takes more than seconds of operation for this
to happen, I'll be impressed. The first time the bearing is operated,
the balls go through the grease like, well, a bunch of bowling balls
through soft butter. If grease needs to be displaced for the balls to
move, it happens almost immediately. The grease has virtually no ability
to resist this displacement. It's also incompressible, and has little
propensity to flow or rebound, so it doesn't return to the bearing track
except as a thin film.

Pumping in more grease also does not remove the contaminated grease
that's already present.


That's exactly what it does. Typical grease-injection hubs have a port
in the hub shell that admits grease into the axle area. the grease can
only flow from there through the bearing and then out the seals. When
clean grease is coming out of the outer seal, there is no place for
contaminated grease to be.

You don't have to believe me. Grease-ported hubs are cheap: pump and see.

--
Ryan Cousineau http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."
  #7  
Old April 11th 08, 08:19 AM posted to rec.bicycles.tech
Lou Holtman
external usenet poster
 
Posts: 86
Default ceramic bearings


"Ryan Cousineau" wrote in message
]...
In article ,
Werehatrack wrote:

On Thu, 10 Apr 2008 05:25:43 GMT, "Dave Mayer"
may have said:

But this brings up the bigger question as to why not just appropriately
maintain your hubs? An even better solution would be to get a hub that

has
a grease injection port. Then, maintenance would amount to a minute

per
year to squeeze some grease into the hub shell and wipe up the old

stuff.

Too much grease increases drag, at least until enough is forced back
out for the grease packs to shear and develop gaps. The amount that
would be present after pumping in enough to actually repack the
bearings would be in that range easily.


If you can demonstrate it takes more than seconds of operation for this
to happen, I'll be impressed. The first time the bearing is operated,
the balls go through the grease like, well, a bunch of bowling balls
through soft butter. If grease needs to be displaced for the balls to
move, it happens almost immediately. The grease has virtually no ability
to resist this displacement. It's also incompressible, and has little
propensity to flow or rebound, so it doesn't return to the bearing track
except as a thin film.

Pumping in more grease also does not remove the contaminated grease
that's already present.


That's exactly what it does. Typical grease-injection hubs have a port
in the hub shell that admits grease into the axle area. the grease can
only flow from there through the bearing and then out the seals. When
clean grease is coming out of the outer seal, there is no place for
contaminated grease to be.


Not true. The pumped in grease seeks the easiest way out. If you see clean
grease comming out there is still contaminated grease inside in the hidden
corners.

You don't have to believe me. Grease-ported hubs are cheap: pump and see.


You don't have to believe me either.

Lou


  #8  
Old April 11th 08, 10:44 PM posted to rec.bicycles.tech
Werehatrack
external usenet poster
 
Posts: 1,416
Default ceramic bearings

On Fri, 11 Apr 2008 07:08:38 GMT, Ryan Cousineau
may have said:

In article ,
Werehatrack wrote:

On Thu, 10 Apr 2008 05:25:43 GMT, "Dave Mayer"
may have said:

But this brings up the bigger question as to why not just appropriately
maintain your hubs? An even better solution would be to get a hub that has
a grease injection port. Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.


Too much grease increases drag, at least until enough is forced back
out for the grease packs to shear and develop gaps. The amount that
would be present after pumping in enough to actually repack the
bearings would be in that range easily.


If you can demonstrate it takes more than seconds of operation for this
to happen, I'll be impressed.


How much are you offering to pay for the bench time? The drag is
small, but everything-weenies being what they are, it would matter to
them. (Probably nobody else, though.) Choice of grease and design of
component might have a lot to do with the clearance time.

The first time the bearing is operated,
the balls go through the grease like, well, a bunch of bowling balls
through soft butter. If grease needs to be displaced for the balls to
move, it happens almost immediately. The grease has virtually no ability
to resist this displacement. It's also incompressible, and has little
propensity to flow or rebound, so it doesn't return to the bearing track
except as a thin film.


Unless, of course, the entire cavity is filled, in which case the
incompressibility means that the balls are running in a viscous
semifluid instead of freely. This is one of the reasons why
pump-lubed hubs are not as common as they used to be, while
aftermarket ball-and-socket joints typically still get supplied with
grease fittings. (The big reason, of course, is that with modern
lubricants and components, the bearings don't require the frequency of
re-lube that old ones needed.)

I recall being told that this used to be a topic in MechE studies;
point being that one should always allow clearance room for the excess
lube to exit. Merely adding a grease fitting to a conventional hub
design is not going to meet the spec.

Pumping in more grease also does not remove the contaminated grease
that's already present.


That's exactly what it does. Typical grease-injection hubs have a port
in the hub shell that admits grease into the axle area. the grease can
only flow from there through the bearing and then out the seals. When
clean grease is coming out of the outer seal, there is no place for
contaminated grease to be.


You've never taken one apart, then? It would be educational. The
contaminated grease will be everywhere that wasn't an active loaded
surface, and the clean grease will have flowed right past it.

You don't have to believe me. Grease-ported hubs are cheap: pump and see.


I used to work on them. I'm glad that modern hubs don't have grease
fittings.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.
  #9  
Old April 12th 08, 01:12 AM posted to rec.bicycles.tech
Camilo
external usenet poster
 
Posts: 183
Default ceramic bearings

On Apr 9, 9:04 pm, Rick Roof wrote:
Just installed ceramic bearings in my front wheel. The original
bearings seem much smoother. Is this just because the ceramics are
not broke in? They just don't seem as smooth as the bearings I took
out. I ended up putting the originals back in for now. Any info
would be appreciated. Thanks.

Rick


I'm wondering if anyone is going to even remotely answer your question
instead of highjacking it for a totally irrelevant discussion. Often
the argument starts with at least a disagreement on actual advice.
Didn't even get that far! I'm curious about your question so I will
stand by (but not hold my breath).
  #10  
Old April 12th 08, 06:46 AM posted to rec.bicycles.tech
Ryan Cousineau
external usenet poster
 
Posts: 4,044
Default ceramic bearings

In article ,
Werehatrack wrote:

On Fri, 11 Apr 2008 07:08:38 GMT, Ryan Cousineau
may have said:

In article ,
Werehatrack wrote:

On Thu, 10 Apr 2008 05:25:43 GMT, "Dave Mayer"
may have said:

But this brings up the bigger question as to why not just appropriately
maintain your hubs? An even better solution would be to get a hub that
has
a grease injection port. Then, maintenance would amount to a minute per
year to squeeze some grease into the hub shell and wipe up the old stuff.

Too much grease increases drag, at least until enough is forced back
out for the grease packs to shear and develop gaps. The amount that
would be present after pumping in enough to actually repack the
bearings would be in that range easily.


If you can demonstrate it takes more than seconds of operation for this
to happen, I'll be impressed.


How much are you offering to pay for the bench time? The drag is
small, but everything-weenies being what they are, it would matter to
them. (Probably nobody else, though.) Choice of grease and design of
component might have a lot to do with the clearance time.

The first time the bearing is operated,
the balls go through the grease like, well, a bunch of bowling balls
through soft butter. If grease needs to be displaced for the balls to
move, it happens almost immediately. The grease has virtually no ability
to resist this displacement. It's also incompressible, and has little
propensity to flow or rebound, so it doesn't return to the bearing track
except as a thin film.


Unless, of course, the entire cavity is filled, in which case the
incompressibility means that the balls are running in a viscous
semifluid instead of freely. This is one of the reasons why
pump-lubed hubs are not as common as they used to be, while
aftermarket ball-and-socket joints typically still get supplied with
grease fittings. (The big reason, of course, is that with modern
lubricants and components, the bearings don't require the frequency of
re-lube that old ones needed.)

I recall being told that this used to be a topic in MechE studies;
point being that one should always allow clearance room for the excess
lube to exit. Merely adding a grease fitting to a conventional hub
design is not going to meet the spec.

Pumping in more grease also does not remove the contaminated grease
that's already present.


That's exactly what it does. Typical grease-injection hubs have a port
in the hub shell that admits grease into the axle area. the grease can
only flow from there through the bearing and then out the seals. When
clean grease is coming out of the outer seal, there is no place for
contaminated grease to be.


You've never taken one apart, then? It would be educational. The
contaminated grease will be everywhere that wasn't an active loaded
surface, and the clean grease will have flowed right past it.


Hm... Okay, I have a lot to learn here, but does this apply to Bearing
Buddy designs, too?

My sense is that at least in the local (rain-dominated) environment,
loss of grease is the fundamental killer of bearings. Lots of grease
prevents water from getting in.

You don't have to believe me. Grease-ported hubs are cheap: pump and see.


I used to work on them. I'm glad that modern hubs don't have grease
fittings.


--
Ryan Cousineau http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."
 




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