Square taper spindle/crank and greasing

[Artoi]

I read that there's a standing recommendation against greasing the
interface b/n a square taper BB spindle and the crank. Further, the
crank bolt shouldn't be greased as well.

Does anyone know the reason why? I initially thought that there's
concern that the crank may work loose and then someone pointed out that
it was to avoid the crank from getting too far up the taper and
potentially split the crank from the corners.

What's the truth? Anyone know the technical explanation for this
recommendation?
--

 

[Mike Jacoubowsky]

>I read that there's a standing recommendation against greasing the
> interface b/n a square taper BB spindle and the crank. Further, the
> crank bolt shouldn't be greased as well.

Don't go there. I am outspokenly against lubricating the square tapers, but
you'll find a number of others who say it makes no difference. You might as
well ask about helmets.

BUT...

Greasing the threads is pretty much universally accepted as the way to go.
You'll find few, if any, arguing that a bolt's surfaces should be dry.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA


"Artoi" <[email protected]> wrote in message
news:[email protected]...
>I read that there's a standing recommendation against greasing the
> interface b/n a square taper BB spindle and the crank. Further, the
> crank bolt shouldn't be greased as well.
>
> Does anyone know the reason why? I initially thought that there's
> concern that the crank may work loose and then someone pointed out that
> it was to avoid the crank from getting too far up the taper and
> potentially split the crank from the corners.
>
> What's the truth? Anyone know the technical explanation for this
> recommendation?
> --

 

[A Muzi]

Artoi wrote:
> I read that there's a standing recommendation against greasing the
> interface b/n a square taper BB spindle and the crank. Further, the
> crank bolt shouldn't be greased as well.
>
> Does anyone know the reason why? I initially thought that there's
> concern that the crank may work loose and then someone pointed out that
> it was to avoid the crank from getting too far up the taper and
> potentially split the crank from the corners.
>
> What's the truth? Anyone know the technical explanation for this
> recommendation?

Good arguments are made both ways. Here, we lube tapers and threads
because we lube every other thread and taper and assume cranks are not
different from other machinery.

There are respected mechanics who assemble tapers dry and report no
returns. Counterintuitive but there it is.

I know no professional mechanics who assemble threads dry.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Artoi]

So what's the rationale for keeping the taper joint dry?
--

 

[still just me]

On Thu, 31 Jan 2008 20:17:40 -0600, A Muzi <[email protected]>
wrote:

>I know no professional mechanics who assemble threads dry.

But torquing a bolt that is lubricated changes the whole torque
equation. If you're one of those guys who uses a torque wrench on
crank bolts, you need to insure that the specs are dry or wet and do
it appropriately.

FWIW - I've removed many crank bolts that had been in place 30 years
and never had an issue getting one loose. However, removing (ungreased
cranks that have been installed for 30 years is sometimes
difficult.

 

[[email protected]]

Artoi who? writes:

> I read that there's a standing recommendation against greasing the
> interface b/n a square taper BB spindle and the crank. Further, the
> crank bolt shouldn't be greased as well.

> Does anyone know the reason why? I initially thought that there's
> concern that the crank may work loose and then someone pointed out
> that it was to avoid the crank from getting too far up the taper and
> potentially split the crank from the corners.

> What's the truth? Anyone know the technical explanation for this
> recommendation?

http://www.sheldonbrown.com/brandt/installing-cranks.html

Jobst Brandt

 

[[email protected]]

On Feb 1, 8:50 am, [email protected] wrote:
> Artoi who? writes:
> > I read that there's a standing recommendation against greasing the
> > interface b/n a square taper BB spindle and the crank. Further, the
> > crank bolt shouldn't be greased as well.
> > Does anyone know the reason why? I initially thought that there's
> > concern that the crank may work loose and then someone pointed out
> > that it was to avoid the crank from getting too far up the taper and
> > potentially split the crank from the corners.
> > What's the truth?  Anyone know the technical explanation for this
> > recommendation?
>
> http://www.sheldonbrown.com/brandt/installing-cranks.html
>
> Jobst Brandt

How is one to avoid repeated re-tightening? After initial
installation, how many times and how often should the bolts be re-
tightened?

Joseph

 

[Peter Cole]

[email protected] wrote:
> On Feb 1, 8:50 am, [email protected] wrote:
>> Artoi who? writes:
>>> I read that there's a standing recommendation against greasing the
>>> interface b/n a square taper BB spindle and the crank. Further, the
>>> crank bolt shouldn't be greased as well.
>>> Does anyone know the reason why? I initially thought that there's
>>> concern that the crank may work loose and then someone pointed out
>>> that it was to avoid the crank from getting too far up the taper and
>>> potentially split the crank from the corners.
>>> What's the truth? Anyone know the technical explanation for this
>>> recommendation?
>> http://www.sheldonbrown.com/brandt/installing-cranks.html
>>
>> Jobst Brandt
>
> How is one to avoid repeated re-tightening? After initial
> installation, how many times and how often should the bolts be re-
> tightened?
>
> Joseph

I've never had to retighten a crank. I grease.

 

[Peter Cole]

Artoi wrote:
> So what's the rationale for keeping the taper joint dry?
> --

I don't think there is one.

 

[[email protected]]

On Feb 1, 1:31 pm, Peter Cole <[email protected]> wrote:
> [email protected] wrote:
> > On Feb 1, 8:50 am, [email protected] wrote:
> >> Artoi who? writes:
> >>> I read that there's a standing recommendation against greasing the
> >>> interface b/n a square taper BB spindle and the crank. Further, the
> >>> crank bolt shouldn't be greased as well.
> >>> Does anyone know the reason why? I initially thought that there's
> >>> concern that the crank may work loose and then someone pointed out
> >>> that it was to avoid the crank from getting too far up the taper and
> >>> potentially split the crank from the corners.
> >>> What's the truth?  Anyone know the technical explanation for this
> >>> recommendation?
> >>http://www.sheldonbrown.com/brandt/installing-cranks.html
>
> >> Jobst Brandt
>
> > How is one to avoid repeated re-tightening? After initial
> > installation, how many times and how often should the bolts be re-
> > tightened?
>
> > Joseph
>
> I've never had to retighten a crank. I grease.

A fine answer! I just replaced a square spindle BB, and I think I'll
pull the crank and reinstall with grease.

I've wondered if my retightening has been necessary due to temperature
changes. Is that plausible?

Joseph

 

[_]

On Fri, 1 Feb 2008 04:35:15 -0800 (PST), [email protected]
wrote:

> On Feb 1, 1:31 pm, Peter Cole <[email protected]> wrote:
>> [email protected] wrote:
>>> On Feb 1, 8:50 am, [email protected] wrote:
>>>> Artoi who? writes:
>>>>> I read that there's a standing recommendation against greasing the
>>>>> interface b/n a square taper BB spindle and the crank. Further, the
>>>>> crank bolt shouldn't be greased as well.
>>>>> Does anyone know the reason why? I initially thought that there's
>>>>> concern that the crank may work loose and then someone pointed out
>>>>> that it was to avoid the crank from getting too far up the taper and
>>>>> potentially split the crank from the corners.
>>>>> What's the truth?  Anyone know the technical explanation for this
>>>>> recommendation?
>>>>http://www.sheldonbrown.com/brandt/installing-cranks.html
>>
>>>> Jobst Brandt
>>
>>> How is one to avoid repeated re-tightening? After initial
>>> installation, how many times and how often should the bolts be re-
>>> tightened?
>>
>>> Joseph
>>
>> I've never had to retighten a crank. I grease.
>
> A fine answer! I just replaced a square spindle BB, and I think I'll
> pull the crank and reinstall with grease.
>
> I've wondered if my retightening has been necessary due to temperature
> changes. Is that plausible?
>

The difference in expansion between aluminium and steel is roughly 4
millionths of an inch per inch per degree. For a 3/4 inch square that
means that a 100 degree increase would result in the fit loosening by 3
ten-thousandths of an inch.

Taper angle is 4 degrees (both sides). That means that such a change in
fit would require the crank to move by about 4 one-thousandths of an inch.

Crank bolt pitch is (usually) 1mm. This means that such a change would
mean that the bolt would have to be turned about 35 degrees to match.

The above is all from mental calculation, with substantial rounding (and
averaging, in the case of co-efficients) of the actual figures; but it
gives an idea of the amount of change required if you install your cranks
outside in Minnesota instead of watching the Stupid Bowl, and then go for a
vacation ride in Guantanamo Bay. Anyone who needs more detailed arithmetic
should ask Bill Sornson - he need the practice.

 

[[email protected]]

On Feb 1, 2:21 pm, _ <[email protected]>
wrote:
> On Fri, 1 Feb 2008 04:35:15 -0800 (PST), [email protected]
> wrote:
>
>
>
> > On Feb 1, 1:31 pm, Peter Cole <[email protected]> wrote:
> >> [email protected] wrote:
> >>> On Feb 1, 8:50 am, [email protected] wrote:
> >>>> Artoi who? writes:
> >>>>> I read that there's a standing recommendation against greasing the
> >>>>> interface b/n a square taper BB spindle and the crank. Further, the
> >>>>> crank bolt shouldn't be greased as well.
> >>>>> Does anyone know the reason why? I initially thought that there's
> >>>>> concern that the crank may work loose and then someone pointed out
> >>>>> that it was to avoid the crank from getting too far up the taper and
> >>>>> potentially split the crank from the corners.
> >>>>> What's the truth?  Anyone know the technical explanation for this
> >>>>> recommendation?
> >>>>http://www.sheldonbrown.com/brandt/installing-cranks.html
>
> >>>> Jobst Brandt
>
> >>> How is one to avoid repeated re-tightening? After initial
> >>> installation, how many times and how often should the bolts be re-
> >>> tightened?
>
> >>> Joseph
>
> >> I've never had to retighten a crank. I grease.
>
> > A fine answer! I just replaced a square spindle BB, and I think I'll
> > pull the crank and reinstall with grease.
>
> > I've wondered if my retightening has been necessary due to temperature
> > changes. Is that plausible?
>
> The difference in expansion between aluminium and steel is roughly 4
> millionths of an inch per inch per degree.  For a 3/4 inch square that
> means that a 100 degree increase would result in the fit loosening by 3
> ten-thousandths of an inch.  
>
> Taper angle is 4 degrees (both sides).  That means that such a change in
> fit would require the crank to move by about 4 one-thousandths of an inch.
>
> Crank bolt pitch is (usually) 1mm.  This means that such a change would
> mean that the bolt would have to be turned about 35 degrees to match.
>
> The above is all from mental calculation, with substantial rounding (and
> averaging, in the case of co-efficients) of the actual figures; but it
> gives an idea of the amount of change required if you install your cranks
> outside in Minnesota instead of watching the Stupid Bowl, and then go for a
> vacation ride in Guantanamo Bay.  Anyone who needs more detailed arithmetic
> should ask Bill Sornson - he need the practice.

What about length of the bolt?

Joseph

 

[_]

On Fri, 1 Feb 2008 05:32:16 -0800 (PST), [email protected]
wrote:

> On Feb 1, 2:21 pm, _ <[email protected]>
> wrote:
>> On Fri, 1 Feb 2008 04:35:15 -0800 (PST), [email protected]
>> wrote:
>>
>>
>>
>>> On Feb 1, 1:31 pm, Peter Cole <[email protected]> wrote:
>>>> [email protected] wrote:
>>>>> On Feb 1, 8:50 am, [email protected] wrote:
>>>>>> Artoi who? writes:
>>>>>>> I read that there's a standing recommendation against greasing the
>>>>>>> interface b/n a square taper BB spindle and the crank. Further, the
>>>>>>> crank bolt shouldn't be greased as well.
>>>>>>> Does anyone know the reason why? I initially thought that there's
>>>>>>> concern that the crank may work loose and then someone pointed out
>>>>>>> that it was to avoid the crank from getting too far up the taper and
>>>>>>> potentially split the crank from the corners.
>>>>>>> What's the truth?  Anyone know the technical explanation for this
>>>>>>> recommendation?
>>>>>>http://www.sheldonbrown.com/brandt/installing-cranks.html
>>
>>>>>> Jobst Brandt
>>
>>>>> How is one to avoid repeated re-tightening? After initial
>>>>> installation, how many times and how often should the bolts be re-
>>>>> tightened?
>>
>>>>> Joseph
>>
>>>> I've never had to retighten a crank. I grease.
>>
>>> A fine answer! I just replaced a square spindle BB, and I think I'll
>>> pull the crank and reinstall with grease.
>>
>>> I've wondered if my retightening has been necessary due to temperature
>>> changes. Is that plausible?
>>
>> The difference in expansion between aluminium and steel is roughly 4
>> millionths of an inch per inch per degree.  For a 3/4 inch square that
>> means that a 100 degree increase would result in the fit loosening by 3
>> ten-thousandths of an inch.  
>>
>> Taper angle is 4 degrees (both sides).  That means that such a change in
>> fit would require the crank to move by about 4 one-thousandths of an inch.
>>
>> Crank bolt pitch is (usually) 1mm.  This means that such a change would
>> mean that the bolt would have to be turned about 35 degrees to match.
>>
>> The above is all from mental calculation, with substantial rounding (and
>> averaging, in the case of co-efficients) of the actual figures; but it
>> gives an idea of the amount of change required if you install your cranks
>> outside in Minnesota instead of watching the Stupid Bowl, and then go for a
>> vacation ride in Guantanamo Bay.  Anyone who needs more detailed arithmetic
>> should ask Bill Sornson - he need the practice.
>
> What about length of the bolt?
>

I did not include that; mental non-calculation indicated that it would be
such a small amount - but let's see.

If the bolt is one inch long, then a 100 degree change will make it about 4
ten-thousandths of an inch shorter after a 100 degree increase than the one
inch of the aluminium of the crank. This is one-tenth of the 1/250th of an
inch indicated above, and the effect is opposite. Perhaps you would need
to turn your bolt 30 degrees instead of 35.

The above does not take into consideration that most of the load in a
bolt-nut situation is taken by only a few threads; that would reduce the
effective length of bolt to be considered, and hence reduce the amount of
change of change. Perhaps you would need to turn your bolt 34 degrees
instead of 35.

 

[[email protected]]

On Feb 1, 1:50 am, [email protected] wrote:

> http://www.sheldonbrown.com/brandt/installing-cranks.html

I have one crank arm that was run loose and has given untroubled
service for years, with at least two further removals for service,
changing bikes and BB's. Heavy rider, hills.

I know of another that was run loose for a 20-mile trip back to town
<g>, and has since been reinstalled and is working just fine.

My problem resulted from retiring from a wrench-twisting job and
(years later) not using a torque wrench after the hand strength had
declined. I don't know about the other one.

In short, "always worth a shot" to inspect, clean, re-grease and put
back on (using the higher range of suggested torque settings); all
cranks are apparently not automatically ruined even after some use
when loose. --D-y

 

[A Muzi]

>> Artoi who? writes:
>>> I read that there's a standing recommendation against greasing the
>>> interface b/n a square taper BB spindle and the crank. Further, the
>>> crank bolt shouldn't be greased as well.
>>> Does anyone know the reason why? I initially thought that there's
>>> concern that the crank may work loose and then someone pointed out
>>> that it was to avoid the crank from getting too far up the taper and
>>> potentially split the crank from the corners.
>>> What's the truth? Anyone know the technical explanation for this
>>> recommendation?

> [email protected] wrote:
>> http://www.sheldonbrown.com/brandt/installing-cranks.html

[email protected] wrote:
> How is one to avoid repeated re-tightening? After initial
> installation, how many times and how often should the bolts be re-
> tightened?

Don't.
If it's properly installed, avoid repetitive tightening as the crank
will 'creep' up the spindle. See also 'cranks' here:
http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html

Riding a poorly installed undertorqued crank can destroy the arm as the
square broach becomes flared and/or rounded with normal cyclic pedal
pressures. All else being equal (or equally deficient) the left will
fail first.

My comments are for traditional square taper aluminum cranks
specifically; Other systems have their own foibles.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[[email protected]]

On Feb 1, 9:05 pm, A Muzi <[email protected]> wrote:
> >> Artoi who? writes:
> >>> I read that there's a standing recommendation against greasing the
> >>> interface b/n a square taper BB spindle and the crank. Further, the
> >>> crank bolt shouldn't be greased as well.
> >>> Does anyone know the reason why? I initially thought that there's
> >>> concern that the crank may work loose and then someone pointed out
> >>> that it was to avoid the crank from getting too far up the taper and
> >>> potentially split the crank from the corners.
> >>> What's the truth?  Anyone know the technical explanation for this
> >>> recommendation?
> >  [email protected] wrote:
> >>http://www.sheldonbrown.com/brandt/installing-cranks.html
> [email protected] wrote:
> > How is one to avoid repeated re-tightening? After initial
> > installation, how many times and how often should the bolts be re-
> > tightened?
>
> Don't.
> If it's properly installed, avoid repetitive tightening as the crank
> will 'creep' up the spindle. See also 'cranks' here:http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html
>
> Riding a poorly installed undertorqued crank can destroy the arm as the
> square broach becomes flared and/or rounded with normal cyclic pedal
> pressures. All else being equal (or equally deficient) the left will
> fail first.
>
> My comments are for traditional square taper aluminum cranks
> specifically; Other systems have their own foibles.
> --
> Andrew Muziwww.yellowjersey.org
> Open every day since 1 April, 1971

I don't use a torque wrench for cranks because I don't have the proper
adapter to use my 1/2" drive torque wrench. So I just use a regular
8mm allen key that is about 5" long I suppose. I crank it to where it
feels like the socket in the bolt is about to deform. This is right
about where it hurts more than I'd like to continue. Should I just do
that once and not ever touch it again?

Joseph

 

[[email protected]]

On Feb 1, 2:30 pm, "[email protected]"
<[email protected]> wrote:

> I don't use a torque wrench for cranks because I don't have the proper
> adapter to use my 1/2" drive torque wrench. So I just use a regular
> 8mm allen key that is about 5" long I suppose. I crank it to where it
> feels like the socket in the bolt is about to deform. This is right
> about where it hurts more than I'd like to continue. Should I just do
> that once and not ever touch it again?

The 1/2" (also 3/8") socket x 8mm hex tool you need is available here
in the USA in automotive supply places as a single tool. Sears, etc.
etc. also might be a source for singles. For "old Campy" users, they
_do too_ make a 7mm hex drive, and it was fun to have the guy at the
counter deny such a tool existed, and the woman employee who knew
better (and also a particular automotive use for that tool) go and
pluck one out of an incoming shipment for me.

The hex side is a little long in the non-bike-specific tools I've
seen, makes use a little cumbersome. But one advantage is, with the
long torque wrench handle, it doesn't hurt the operator <g>.

I've looked on the Park tool site but they don't seem to have a bike-
specific tool on offer.

After my dad explained a little about mfg. tolerances affecting torque
specs ("lube everything" was the word from him), he said "it's still
the best shot you have". Suffice to say, the time I didn't use the
torque wrench he bought me back then, my left crank "fell off". --D-y

 

[A Muzi]

>>>> Artoi who? writes:
>>>>> I read that there's a standing recommendation against greasing the
>>>>> interface b/n a square taper BB spindle and the crank. Further, the
>>>>> crank bolt shouldn't be greased as well.
>>>>> Does anyone know the reason why? I initially thought that there's
>>>>> concern that the crank may work loose and then someone pointed out
>>>>> that it was to avoid the crank from getting too far up the taper and
>>>>> potentially split the crank from the corners.
>>>>> What's the truth? Anyone know the technical explanation for this
>>>>> recommendation?

>>> [email protected] wrote:
>>>> http://www.sheldonbrown.com/brandt/installing-cranks.html

>> [email protected] wrote:
>>> How is one to avoid repeated re-tightening? After initial
>>> installation, how many times and how often should the bolts be re-
>>> tightened?

> A Muzi <[email protected]> wrote:
>> Don't.
>> If it's properly installed, avoid repetitive tightening as the crank
>> will 'creep' up the spindle. See also 'cranks' here:http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html
>> Riding a poorly installed undertorqued crank can destroy the arm as the
>> square broach becomes flared and/or rounded with normal cyclic pedal
>> pressures. All else being equal (or equally deficient) the left will
>> fail first.
>> My comments are for traditional square taper aluminum cranks
>> specifically; Other systems have their own foibles.

> I don't use a torque wrench for cranks because I don't have the proper
> adapter to use my 1/2" drive torque wrench. So I just use a regular
> 8mm allen key that is about 5" long I suppose. I crank it to where it
> feels like the socket in the bolt is about to deform. This is right
> about where it hurts more than I'd like to continue. Should I just do
> that once and not ever touch it again?

Thats' right.
Jobst's FAQ entry referenced above is quite good on this subject.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[John Henderson]

[email protected] wrote:

> I don't use a torque wrench for cranks because I don't have
> the proper adapter to use my 1/2" drive torque wrench. So I
> just use a regular 8mm allen key that is about 5" long I
> suppose. I crank it to where it feels like the socket in the
> bolt is about to deform. This is right about where it hurts
> more than I'd like to continue. Should I just do that once and
> not ever touch it again?

Yes, but after torquing with 70 lb pressure on that 5" of
leverage. You may not be achieving anything like that though.

John

 

[Artoi]

In article <[email protected]>,
[email protected] wrote:

> Artoi who? writes:
>
> > I read that there's a standing recommendation against greasing the
> > interface b/n a square taper BB spindle and the crank. Further, the
> > crank bolt shouldn't be greased as well.
>
> > Does anyone know the reason why? I initially thought that there's
> > concern that the crank may work loose and then someone pointed out
> > that it was to avoid the crank from getting too far up the taper and
> > potentially split the crank from the corners.
>
> > What's the truth? Anyone know the technical explanation for this
> > recommendation?
>
> http://www.sheldonbrown.com/brandt/installing-cranks.html
>
> Jobst Brandt

Thanks. Originally I thought it was Sheldon's words, but then found that
you were the author.
--