Do plastic BB cups need to be greased?
Andre Jute
does one just let them sit there without service until the BB gives up
the ghost?
Andre Jute
I'm not a know-all. I don't need to be. I know whom to ask.
RobertH
> Do plastic bottom cups need to be greased at the annual service? Or
> does one just let them sit there without service until the BB gives up
> the ghost?
The plastic cup is not supposed to be greased ever. I don't think it
really matters that much whether you do or not though.
Kerry Montgomery
"RobertH" <r15...@aol.com> wrote in message
news:65431f23-aac1-4440...@f14g2000pre.googlegroups.com...
But,
There are some plastics that are not compatible with some greases = the
grease attacks the plastic and degrades it.
Kerry
Jobst Brandt
>> Do plastic bottom cups need to be greased at the annual service?
>> Or does one just let them sit there without service until the BB
>> gives up the ghost?
I don't know about "sit there" but rotating requires lubrication.
> The plastic cup is not supposed to be greased ever. I don't think
> it really matters that much whether you do or not though.
In that perspective, what serves as a lubricant? These units use ball
bearings, and balls, to have contact area, must run in a curved race.
Geometry makes clear that the center of a contacting ball moves faster
than its edge, requiring the balls to partially slide, for which there
must be a lubricant.
A thorough treatise about this can be found in the corner stone of
bearing analyses:
"Rolling Bearing Analysis" by Tedric A. Harris.
Jobst Brandt
Andre Jute
bearings on plastic. They're merely threaded holder rings for a metal
shell which contains sealed bearings. The greasing I refer to is
between the plastic thread of this holder ring and the bottom bracket
shell which is part of the frame. If I misled you by careless
terminology, I apologize. -- AJ
landotter
You want a slight bit of nose grease from a gypsy.
Andre Jute
Occasionally you do get something nearly right, Maxine. But the nose
grease is from the sweat glands and is used in watchmaking. Old
jewelers would touch their noses and then the innards of your watch
for a reason. -- Andre Jute
Jobst Brandt
>>>> Do plastic bottom cups need to be greased at the annual service?
>>>> Or does one just let them sit there without service until the BB
>>>> gives up the ghost?
>> I don't know about "sit there" but rotating requires lubrication.
>>> The plastic cup is not supposed to be greased ever. I don't think
>>> it really matters that much whether you do or not though.
>> In that perspective, what serves as a lubricant? These units use
>> ball bearings, and balls, to have contact area, must run in a
>> curved race. Geometry makes clear that the center of a contacting
>> ball moves faster than its edge, requiring the balls to partially
>> slide, for which there must be a lubricant.
>> A thorough treatise about this can be found in the corner stone of
>> bearing analyses:
>> "Rolling Bearing Analysis" by Tedric A. Harris.
> Hold your horses, Jobst. These cups I mention don't carry ball
> bearings on plastic. They're merely threaded holder rings for a
> metal shell which contains sealed bearings. The greasing I refer to
> is between the plastic thread of this holder ring and the bottom
> bracket shell which is part of the frame. If I misled you by
> careless terminology, I apologize.
Oops, this seems to be more a matter of stating the problem than how
to solve it. The description didn't appear to be anything but a BB
spindle bearing mechanism. I guess it wasn't, but in that event,
forces great enough to destroy threads in steel BB shells are great
enough to make plastic flow. I haven't seen one of the devices
apparently being discussed so my comments have no value for the OP.
Jobst Brandt
Tom Sherman °_°
> Andre Jute wrote:
> [...]
>> Hold your horses, Jobst. These cups I mention don't carry ball
>> bearings on plastic. They're merely threaded holder rings for a
>> metal shell which contains sealed bearings. The greasing I refer to
>> is between the plastic thread of this holder ring and the bottom
>> bracket shell which is part of the frame. If I misled you by
>> careless terminology, I apologize.
>
> Oops, this seems to be more a matter of stating the problem than how
> to solve it. The description didn't appear to be anything but a BB
> spindle bearing mechanism. I guess it wasn't, but in that event,
> forces great enough to destroy threads in steel BB shells are great
> enough to make plastic flow. I haven't seen one of the devices
> apparently being discussed so my comments have no value for the OP.
>
> Jobst Brandt
I believe something like this is what is being discussed:
<http://images.jensonusa.com/large/bb/bb309f05blk.jpg>.
--
Tom Sherman - 42.435731,-83.985007
RobertH
> But,
> There are some plastics that are not compatible with some greases = the
> grease attacks the plastic and degrades it.
Yeah but the thing is going to break in about two months anyway. Also
when it breaks it will probably work about as well as it does
unbroken. Therefore I conclude not to worry too much about getting
grease on the plastic thing.
Jobst Brandt
>>> Hold your horses, Jobst. These cups I mention don't carry ball
>>> bearings on plastic. They're merely threaded holder rings for a
>>> metal shell which contains sealed bearings. The greasing I refer to
>>> is between the plastic thread of this holder ring and the bottom
>>> bracket shell which is part of the frame. If I misled you by
>>> careless terminology, I apologize.
>> Oops, this seems to be more a matter of stating the problem than how
>> to solve it. The description didn't appear to be anything but a BB
>> spindle bearing mechanism. I guess it wasn't, but in that event,
>> forces great enough to destroy threads in steel BB shells are great
>> enough to make plastic flow. I haven't seen one of the devices
>> apparently being discussed, so my comments have no value for the OP.
> I believe something like this is what is being discussed:
http://images.jensonusa.com/large/bb/bb309f05blk.jpg
... and further, what that device is is completely unclear to those
who do not have one in hand. This plastic item with a large external
flange appears to waste much BB width on a toothed recess for
installation and removal. The bearing that it apparently adjusts is
not shown, nor is a cross section of how it works. That returns this
subject to the outset where nothing was known nor can be advised.
Jobst Brandt
Tom Sherman °_°
These two pictures should edify.
<http://www.evanscycles.com/product_image/image/d7d/5d3/12b/27919/product_page/shimano-un54-bottom-bracket.jpg>
<http://www.evanscycles.com/product_image/image/e1f/dd4/a2e/27920/product_page/shimano-un54-bottom-bracket-e-type.jpg>
Your LBS likely has a couple dozen of these cartridge bottom brackets
you can examine. I have a couple around with junk bearings I could send
to you to dissect and examine, if you wish, and your LBS could likely
provide you with the same if you ask.
Jobst Brandt
>>>>> Hold your horses, Jobst. These cups I mention don't carry ball
>>>>> bearings on plastic. They're merely threaded holder rings for a
>>>>> metal shell which contains sealed bearings. The greasing I refer to
>>>>> is between the plastic thread of this holder ring and the bottom
>>>>> bracket shell which is part of the frame. If I misled you by
>>>>> careless terminology, I apologize.
>>>> Oops, this seems to be more a matter of stating the problem than how
>>>> to solve it. The description didn't appear to be anything but a BB
>>>> spindle bearing mechanism. I guess it wasn't, but in that event,
>>>> forces great enough to destroy threads in steel BB shells are great
>>>> enough to make plastic flow. I haven't seen one of the devices
>>>> apparently being discussed, so my comments have no value for the OP.
>>> I believe something like this is what is being discussed:
http://images.jensonusa.com/large/bb/bb309f05blk.jpg
>> ... and further, what that device is is completely unclear to those
>> who do not have one in hand. This plastic item with a large external
>> flange appears to waste much BB width on a toothed recess for
>> installation and removal. The bearing that it apparently adjusts is
>> not shown, nor is a cross section of how it works. That returns this
>> subject to the outset where nothing was known nor can be advised.
> These two pictures should edify.
> Your LBS likely has a couple dozen of these cartridge bottom
> brackets you can examine. I have a couple around with junk bearings
> I could send to you to dissect and examine, if you wish, and your
> LBS could likely provide you with the same if you ask.
Yes that makes the outside of the BB unit clear and that they believe
plastic can support the load. Even though the right side is steel, I
am not convinced that the left side is adequate in plastic. The
difference is that there is no direct chain load on the left but there
is chain load from leverage across from the right. That the left side
can survive with a right hand thread indicates that the transferred
chain load is not large, although if the lock ring isn't tight, the
left hand cup could unscrew if it had a left hand thread. Aren't we
lucky on that side.
As you see, with some conical pieces, other people have given this
sore point some attention. I believe they have not yet found a
durable design.
Jobst Brandt
Lou Holtman
This plastic item doesn't adjust no bearings. The bearings and spindle
are held in a separate shell/cartridge. This plastic item along with
another one on the other side keep this cartridge in place in the
bottom bracket shell. It can be made out of plastic but I prefer the
metal one that is common with the more expensive versions. If you like
I can take a picture off one I have in my spare part bin.
Lou
Andre Jute
> Yes that makes the outside of the BB unit clear and that they believe
> plastic can support the load. Even though the right side is steel, I
> am not convinced that the left side is adequate in plastic. The
> difference is that there is no direct chain load on the left but there
> is chain load from leverage across from the right. That the left side
> can survive with a right hand thread indicates that the transferred
> chain load is not large, although if the lock ring isn't tight, the
> left hand cup could unscrew if it had a left hand thread. Aren't we
> lucky on that side.
>
> As you see, with some conical pieces, other people have given this
> sore point some attention. I believe they have not yet found a
> durable design.
>
> Jobst Brandt
You must admit, Jobst, that is bizarre when a bicycle component
designer like you appears to be ignorant of the commonest form of
bottom bracket, and the adaptors that fit it to the frame. (Help us
out here, Carl: when was the sealed bottom bracket invented, and when
did it become a routine, commonplace fitment?)
The bottom bearing in question in my original post is a Kinex with
*plastic cups both sides*. It is made by quality bearing-makers who do
not make novice mistakes:
http://www.kinex.sk/english/index.php
You can see an exploded drawing of their bottom bracket, including the
adaptor cups on p8ff in their catalogue:
http://www.kinex.sk/dokumenty/1238655918.pdf
Kinex bottom brackets are fitted by top European makers including
Utopia, Pedersen, Koga Miyata, Gazelle, the usual upmarket German and
Swiss makers, and so on. The plastic cup models are particularly
treasured by makers who make IGH bikes because they have a certain
amount of flex built into the lip which does not destroy full
chaincases as the metal adaptor cups do. Since these are people with
their minds in gear, who give long guarantees (ten years on a couple
of my bikes where I remember the guarantee term offhand) and must keep
their reputations pristine if they want to keep charging a premium for
their bicycles, you may assume that they find the Kinex more than good
enough. There is absolutely no evidence that the plastic cups are not
more than good enough, or break, or give any trouble whatsoever.
Andre Jute
Not everything in materials is dreamt of in Timoshenko
AMuzi
>> But,
>> There are some plastics that are not compatible with some greases = the
>> grease attacks the plastic and degrades it.
RobertH wrote:
> Yeah but the thing is going to break in about two months anyway. Also
> when it breaks it will probably work about as well as it does
> unbroken. Therefore I conclude not to worry too much about getting
> grease on the plastic thing.
I disagree.
These have been around for over twenty years and experience
has shown otherwise.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
Tom Sherman °_°
Problems with the plastic cups does not seem to be reported. Maybe one
or more of the LBS proprietors that frequent RBT will share their
experience on this common bottom bracket design.
AMuzi
carry ball
>>>> bearings on plastic. They're merely threaded holder rings for a
>>>> metal shell which contains sealed bearings. The greasing I refer to
>>>> is between the plastic thread of this holder ring and the bottom
>>>> bracket shell which is part of the frame. If I misled you by
>>>> careless terminology, I apologize.
>>> Oops, this seems to be more a matter of stating the problem than how
>>> to solve it. The description didn't appear to be anything but a BB
>>> spindle bearing mechanism. I guess it wasn't, but in that event,
>>> forces great enough to destroy threads in steel BB shells are great
>>> enough to make plastic flow. I haven't seen one of the devices
>>> apparently being discussed, so my comments have no value for the OP.
> Tom Sherman wrote:
>> I believe something like this is what is being discussed:
>> http://images.jensonusa.com/large/bb/bb309f05blk.jpg
Jobst Brandt wrote:
> ... and further, what that device is is completely unclear to those
> who do not have one in hand. This plastic item with a large external
> flange appears to waste much BB width on a toothed recess for
> installation and removal. The bearing that it apparently adjusts is
> not shown, nor is a cross section of how it works. That returns this
> subject to the outset where nothing was known nor can be advised.
Imagine something roughly like a Phil Wood BB cartridge but
with nylon sleeves to mount it:
http://pic.pimg.tw/ss923/normal_1199895046.png
The ACH model shown has steel or aluminum mounts but the
dimensions (and bearing unit) are the same as the earlier
nylon version.
Jobst Brandt
>>>>> Hold your horses, Jobst. These cups I mention don't carry ball
>>>>> bearings on plastic. They're merely threaded holder rings for a
>>>>> metal shell which contains sealed bearings. The greasing I
>>>>> refer to is between the plastic thread of this holder ring and
>>>>> the bottom bracket shell which is part of the frame. If I
>>>>> misled you by careless terminology, I apologize.
>>>> Oops, this seems to be more a matter of stating the problem than
>>>> how to solve it. The description didn't appear to be anything
>>>> but a BB spindle bearing mechanism. I guess it wasn't, but in
>>>> that event, forces great enough to destroy threads in steel BB
>>>> shells are great enough to make plastic flow. I haven't seen one
>>>> of the devices apparently being discussed, so my comments have no
>>>> value for the OP.
>>> I believe something like this is what is being discussed:
http://images.jensonusa.com/large/bb/bb309f05blk.jpg
>> ... and further, what that device is is completely unclear to those
>> who do not have one in hand. This plastic item with a large
>> external flange appears to waste much BB width on a toothed recess
>> for installation and removal. The bearing that it apparently
>> adjusts is not shown, nor is a cross section of how it works. That
>> returns this subject to the outset where nothing was known nor can
>> be advised.
> Imagine something roughly like a Phil Wood BB cartridge but with
> nylon sleeves to mount it:
http://pic.pimg.tw/ss923/normal_1199895046.png
> The ACH model shown has steel or aluminum mounts but the dimensions
> (and bearing unit) are the same as the earlier nylon version.
I notice that none of these web sites show a cutaway drawing from
which one might see whether these are 1/4" balls as the ones they
replace, or whether they are angular contact, something needed
for axial loads that are large in the BB.
The whole subject strikes me as a dodge and weave exercise, relying on
bicyclist's belief in the superiority of cartridge bearings. I
believe that Shimano threadless head bearings have demonstrated the
need for job specific angular contact bearings on bicycles, and that
classic high speed radial ball bearings have no place with the
relatively high loads and low speeds on bicycles.
Jobst Brandt
thirty-six
You should install the unit without greasing the threads using a tight
fitting spanner. The heat generated will conform the plastic threads
to an accurate fit in the bracket shell. Greasing the threads
actually can make installation more tiring because the thread
maintains an excessive resistance. So, no. Without daily wet weather
use, you should get at least four years out of one of those units. If
you want longer, drill the centre and pump fluid grease after two
years.
RobertH
> > "Kerry Montgomery" <kamon...@teleport.com> wrote:
> >> But,
> >> There are some plastics that are not compatible with some greases = the
> >> grease attacks the plastic and degrades it.
> RobertH wrote:
> > Yeah but the thing is going to break in about two months anyway. Also
> > when it breaks it will probably work about as well as it does
> > unbroken. Therefore I conclude not to worry too much about getting
> > grease on the plastic thing.
>
> I disagree.
> These have been around for over twenty years and experience
> has shown otherwise.
My 20-year experience with these is that they break frequently and
often, and that it usually doesn't matter too much if they do. If 100
people went out and removed their BBs I'd bet about 70 of them would
find the plastic cup completely cracked through already without their
knowledge.
Andre Jute
Last year I rode that bike 2227km. I reckon a bottom bracket should
last ten years minimum with my light use; there are probably dozens of
correspondents here who ride that sort of mileage every couple of
months and you just don't hear of them fitting new bottom brackets
every few months. I'm not impressed with the disdain on RBT for the
cheaper bottom brackets like the UN26. The attitude may have historic
roots among a generally aging (and sometimes bizarrely luddite)
newsgroup population, but the number of quality manufacturers who fit
such bottom brackets to even their most expensive models tells a
different story. Unless the bicycle's application and use is extreme,
anything more expensive than a UN54 seems overkill.
>If
> you want longer, drill the centre and pump fluid grease after two
> years.
How do I drill the bottom bracket without getting metal shavings in
the gubbins? (This is a hypothetical question. A bottom bracket for
under 25 euro is clearly a modular chuck and replace unit.) How do I
even get the grease to the bearings? That's the point of a sealed
unit, Trevor. Check the cutaway drawing in the Kinex PDF the URL of
which I posted above a few hours ago, and you'll see what I mean: it
appears that there is no way to reach those bearings.
Andre Jute
"By definition, the presence of a cam tells you it's not 2-stroke."
-- "jim beam", internet ignoramus, proving his "competence"
thirty-six
> How do I drill the bottom bracket without getting metal shavings in
> the gubbins?
Carefully with a hand drill and grease on the bit.
(This is a hypothetical question. A bottom bracket for
> under 25 euro is clearly a modular chuck and replace unit.)
The work involved in making it an everlasting unit is less than that
required for replacement.
How do I
> even get the grease to the bearings? That's the point of a sealed
> unit, Trevor. Check the cutaway drawing in the Kinex PDF the URL of
> which I posted above a few hours ago, and you'll see what I mean: it
> appears that there is no way to reach those bearings.
Unless you drill the centre to permit re-pressurisation by topping up
with grease.
Chalo
>
> Problems with the plastic cups does not seem to be reported. Maybe one
> or more of the LBS proprietors that frequent RBT will share their
> experience on this common bottom bracket design.
Plastic retaining rings are only trouble when you go to remove them,
and they break (which is relatively commonplace in my shop). Before
that time, they work fine. There is little reason to remove a
cartridge BB before it develops play in its bearings-- at which time
it must be replaced anyway.
I always grease the plastic retaining rings, not so much to lubricate
them but rather to help prevent corrosion in dry frame threads.
Cartridge BBs are generally more reliable and trouble-free than
traditional cup and cone units. At the low end of the price range,
they make good sense because they outperform similarly cheap cup and
cone BBs. Expensive, high quality BBs are probably better as cup and
cone versions, because their adjustability and maintainability are
likely to give them significantly longer life.
My biggest misgiving with cartridge BBs is their large and unnecessary
amount of overhang at the spindle ends. This makes cranks mounted on
them noticeably more flexible than the same cranks mounted on cup and
cone BBs.
When it matters, cup and cone BBs are often preferable because they
can be had with stronger nutted spindles. These are much less likely
to break compared to spindles that are drilled for bolts, as are all
square taper cartridge BBs.
Chalo
Chalo
>
> The whole subject strikes me as a dodge and weave exercise, relying on
> bicyclist's belief in the superiority of cartridge bearings.
Inexpensive cartridge BBs seem to have a better chance at decent
longevity than the inexpensive cup and cone BBs of yore, and in the
interim they require no maintenance whatsoever. For most people, that
represents a good bargain.
A scrupulously adjusted, well sealed, and adequately maintained
traditional BB will outlast an equivalent cartridge unit. But such
BBs have always been the exception.
Chalo
Peter Cole
I agree, having several bikes with both designs. When a cup & spindle BB
goes, I always try to replace it with a cartridge type, most often a
UN54. It costs the same, and you don't have to worry about finding a
spindle compatible with your cups, nor do you have to fuss with preload.
I have never had much trouble with the plastic adapters. Sometimes they
get stuck enough that the age-brittle plastic teeth break at removal
time, but they're easy enough to hack out. It wouldn't hurt to lube the
plastic threads, but it's hardly necessary. I'd use regular anti-seize,
mostly because that's what I'd use on the other side (metal on UN54),
but if you're concerned about degrading the plastic with oil, use
silicone (e.g. dielectric grease). I have never greased the plastic, but
I might if both sides were made of it.
The other "standard" BB thread treatment is teflon tape. I'm not sure
how well that would work, as my memory is that the plastic threads don't
seem to have much clearance, being soft enough to conform to the BB
shell threads.
>> If
>> you want longer, drill the centre and pump fluid grease after two
>> years.
>
> How do I drill the bottom bracket without getting metal shavings in
> the gubbins? (This is a hypothetical question. A bottom bracket for
> under 25 euro is clearly a modular chuck and replace unit.) How do I
> even get the grease to the bearings? That's the point of a sealed
> unit, Trevor. Check the cutaway drawing in the Kinex PDF the URL of
> which I posted above a few hours ago, and you'll see what I mean: it
> appears that there is no way to reach those bearings.
My memory is dim, but I recall one time adding grease to a UN54 type
without removing it. I think I pried up the seal and replaced it after
greasing. It was only a temporary measure on a dying unit, because, as
you point out, maintenance defeats the purpose of these units. I suppose
those more frugal than myself (hard to imagine) could do that regularly
with a needle adapter on a grease gun, drilling a small hole in the
seal if necessary.
Peter Cole
> My biggest misgiving with cartridge BBs is their large and unnecessary
> amount of overhang at the spindle ends. This makes cranks mounted on
> them noticeably more flexible than the same cranks mounted on cup and
> cone BBs.
I'll take your word for it, but I'm surprised, given how much flex there
is usually in the BB shell/frame. I have noticed my Cannondales feeling
significantly stiffer under hard pedaling, and I like the feeling, but
I'd have a hard time arguing that it's a big improvement for any
practical reason.
> When it matters, cup and cone BBs are often preferable because they
> can be had with stronger nutted spindles. These are much less likely
> to break compared to spindles that are drilled for bolts, as are all
> square taper cartridge BBs.
I often get spalling on my spindles, maybe that reflects on their
quality, my size, or both, so the only thing I'm retaining in a rebuild
is the cups. Given the fatigue consequences, perhaps it's not such a bad
thing to discard spindles after a finite service period.
Jay Beattie
The "well sealed" part was a problem in days of yore, being that the
Campy NR had no seals, and neither did the hubs (except for "dust
caps"). Some of the Japanese manufacturers added wipers, but at about
that time, the market started shifting to cartridge bearings, IIRC.
For Jobst, SKF does offer a cartridge BB with roller bearings, but
most use conventional ball bearings. -- Jay Beattie.
Jobst Brandt
They do that for good reason. Rollers want to run in smooth
cylindrically aligned races, but a BB spindles flex enough to cause
roller misalignment and overload failures. We had roller bearing BB's
more than 20 years ago and they all failed in a hurry. The bait and
switch of that may be from lack of technical understanding, but it
plays on the concept that rollers can carry more load than balls and
because they roll and don't slide as balls in ball bearings do, give
lower drag... they don't!
Jobst Brandt
Michael Press
<df2478c4-d659-459f...@z4g2000yqa.googlegroups.com>,
Chalo <chalo....@gmail.com> wrote:
> When it matters, cup and cone BBs are often preferable because they
> can be had with stronger nutted spindles. These are much less likely
> to break compared to spindles that are drilled for bolts, as are all
> square taper cartridge BBs.
Do drilled spindles break at the drilling?
I thought they mostly break at external stress risers.
--
Michael Press
Andre Jute
> Do plastic bottom cups need to be greased at the annual service? Or
> does one just let them sit there without service until the BB gives up
> the ghost?
>
> Andre Jute
> I'm not a know-all. I don't need to be. I know whom to ask.
Thanks to all for opinions and advice. In summary:
1. The only good reason for greasing plastic adaptor cup threads is so
that dry threads in the bottom bracket shell do not corrode (Chalo).
2. There is in fact no good reason for me to remove this bottom
bracket with a plastic cup each end until it fails, and then the
materials of the new bottom bracket will determine whether I need to
apply grease.
Chalo
>
> Chalo wrote:
> >
> > My biggest misgiving with cartridge BBs is their large and unnecessary
> > amount of overhang at the spindle ends. This makes cranks mounted on
> > them noticeably more flexible than the same cranks mounted on cup and
> > cone BBs.
>
> I'll take your word for it, but I'm surprised, given how much flex there
> is usually in the BB shell/frame. I have noticed my Cannondales feeling
> significantly stiffer under hard pedaling, and I like the feeling, but
> I'd have a hard time arguing that it's a big improvement for any
> practical reason.
True BB sway in the frame is more or less a matter of taste. Flex in
the BB spindle affects front shifting, a lot. And my observations
lead me to believe that there is more flex in a typical square taper
crank and spindle than there is in a typical frame around the BB
shell.
If you were to install a tubular CrMo BMX crank on a traditional
diameter lugged steel frame, I think you'd find it to feel stiffer
overall than an older big-tube Cannondale with an aluminum square-
taper crank. It sure would do a lot less grating on the front
derailleur.
I remember when cartridge BBs first made the scene in 1992. I was
working at my first bike shop job, mostly doing original assembly of
new bikes. The first cartridge BBs I saw came in on the Specialized
Rockhoppers we had gotten as replacements for the rental fleet. At
the time, I was riding a Cannondale MTB with 196mm Bullseye cranks, so
that's what I was used to. But I did a lot of test riding of
different bikes in the process of checking out repairs and new builds,
so I was familiar with other things too.
When I finished assembling the first of these cartridge BB equipped
Rockhoppers, I went out to test it. With my first couple of hard
pedal strokes, I thought I had broken the bike, because the pedals
swayed so far underneath the BB. It was really unnerving to me, and I
curtailed the test ride.
I gave up riding on square taper cranks after breakages and a serious
injury, but I have never been sure whether the additional flex in a
cartridge BB would make it more likely or less likely to fracture at
the root of the square taper. I'm thinking it might be a little less
likely because of the broader distribution of stress in the part. But
the broken ones I see at the shop these days (fatigued and snapped in
the same old way by large, strong riders) are all cartridges, because
that's mostly what folks are using now.
> > When it matters, cup and cone BBs are often preferable because they
> > can be had with stronger nutted spindles. These are much less likely
> > to break compared to spindles that are drilled for bolts, as are all
> > square taper cartridge BBs.
>
> I often get spalling on my spindles, maybe that reflects on their
> quality, my size, or both, so the only thing I'm retaining in a rebuild
> is the cups. Given the fatigue consequences, perhaps it's not such a bad
> thing to discard spindles after a finite service period.
That seems like a good and prudent practice. All the same, I have yet
to see a nutted spindle that broke off at the end the way bolted ones
do every so often.
Chalo
Peter Cole
Good to know. As Sheldon used to say -- it's good to learn from one's
mistakes, better to learn from others...
These days, I may ride fast and may ride out of the saddle, but not so
much at the same time any more.
thirty-six
> Tom Sherman wrote:
>
> > Problems with the plastic cups does not seem to be reported. Maybe one
> > or more of the LBS proprietors that frequent RBT will share their
> > experience on this common bottom bracket design.
>
> Plastic retaining rings are only trouble when you go to remove them,
> and they break (which is relatively commonplace in my shop). Before
> that time, they work fine. There is little reason to remove a
> cartridge BB before it develops play in its bearings-- at which time
> it must be replaced anyway.
Or live with it. Doesn't seem quite so bad when the bike is stolen
and there is a part that needs replacing.
>
> I always grease the plastic retaining rings, not so much to lubricate
> them but rather to help prevent corrosion in dry frame threads.
Petroleum based lubricants (mineral oil/grease) will deteriorate
petroleum based polymers (plastics).
Zinc and castor oil cream would be OK if you wish to use gunk.
>