Grease BB spindle?

[Jobst Brandt]

Right from the Shimano web site inder FAQ: http://www.shimano-europe.com/cycling/
----------------------------------------------------------------------
Question:

Do I have to use some grease on the spindle of a square bottom bracket?

Answer:

No this is not recommended to do so. Reason for this is that the square bottom brackets have a
tapered spindle, so in case you would assemble and disassemble the crankset a few times, assemble it
with grease again and tighten the crankbolt, the crank will be pushed onto the spindle more and
more. The stress on the square hole of the crank will become so high that it might break. Tightening
torque for the crankbolt should be 35-50 Nm.

On the other hand, for the splined bottom brackets we do recommend to apply some grease onto the
spindle. As this type of spindle does not have a tapered spindle, there is no risk of stress on the
hole of the crank for assembly with grease.
----------------------------------------------------------------------

There you have it. I am amazed at the blinders the authors of this advice must be wearing, oblivious
to material science and prestressed interfaces. Their description makes the crank appear to be made
of a plastic material rather than an metal. Just the idea that the crank is loaded to its yield
stress, the stress where permanent deformation takes place, is absurd. At that stress the crank
would fail in less than a hundred miles of use.

Who are these people!

Jobst Brandt [email protected] Palo Alto CA

 

[The Pomeranian]

[email protected] wrote:
>
> Right from the Shimano web site inder FAQ: http://www.shimano-europe.com/cycling/
> ----------------------------------------------------------------------
> Question:
>
> Do I have to use some grease on the spindle of a square bottom bracket?
>
> Answer:
>
> No this is not recommended to do so. Reason for this is that the square bottom brackets have a
> tapered spindle, so in case you would assemble and disassemble the crankset a few times, assemble
> it with grease again and tighten the crankbolt, the crank will be pushed onto the spindle more and
> more. The stress on the square hole of the crank will become so high that it might break.
> Tightening torque for the crankbolt should be 35-50 Nm.
>
> On the other hand, for the splined bottom brackets we do recommend to apply some grease onto the
> spindle. As this type of spindle does not have a tapered spindle, there is no risk of stress on
> the hole of the crank for assembly with grease.
> ----------------------------------------------------------------------
>
> There you have it. I am amazed at the blinders the authors of this advice must be wearing,
> oblivious to material science and prestressed interfaces. Their description makes the crank appear
> to be made of a plastic material rather than an metal. Just the idea that the crank is loaded to
> its yield stress, the stress where permanent deformation takes place, is absurd. At that stress
> the crank would fail in less than a hundred miles of use.
>
> Who are these people!

They are the ones you've been meaning to write that email to, about colletted cranks. Good
luck, sucker.

 

[Phil Holman]

<[email protected]> wrote in message news:[email protected]...
> Right from the Shimano web site inder FAQ: http://www.shimano-europe.com/cycling/
> ----------------------------------------------------------------------
> Question:
>
> Do I have to use some grease on the spindle of a square bottom bracket?
>
> Answer:
>
> No this is not recommended to do so. Reason for this is that the square bottom brackets have a
> tapered spindle, so in case you would assemble and disassemble the crankset a few times, assemble
> it with grease again and tighten the crankbolt, the crank will be pushed onto the spindle more and
> more. The stress on the square hole of the crank will become so high that it might break.
> Tightening torque for the crankbolt should be 35-50 Nm.
>
> On the other hand, for the splined bottom brackets we do recommend to apply some grease onto the
> spindle. As this type of spindle does not have a tapered spindle, there is no risk of stress on
> the hole of the crank for assembly with grease.
> ----------------------------------------------------------------------
>

Not an accurate discription of the spindle which does have a tapered portion. I estimate the splines
bottom out well within the elastic range of the crankarm's tapered interface thus precluding the
possibility of running it too far up the taper.

> There you have it. I am amazed at the blinders the authors of this advice must be wearing,
> oblivious to material science and prestressed interfaces. Their description makes the crank appear
> to be made of a plastic material rather than an metal. Just the idea that the crank is loaded to
> its yield stress, the stress where permanent deformation takes place, is absurd. At that stress
> the crank would fail in less than a hundred miles of use.
>
> Who are these people!

The same people I wrestle with to get DSL running on my computer :-(

Phil Holman

 

[John Stevenson]

[email protected] wrote:

> Who are these people!

Marketing.

--
John Stevenson [email protected]

 

[Qui Si Parla Ca]

jobst-<< I am amazed at the blinders the authors of this advice must be wearing, oblivious to
material science and prestressed interfaces.

<< Who are these people!

Why don't you ask them why they say what they do? Instead of posting on a NG that you yourself call
'wreck'....

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

[Steve Shapiro]

Campy also says don't grease the square spindle or hole. In fact, they say to be careful to
de-grease these areas. You can read all about it by downloading their crankset instructions. But
I've used grease all my life (60 now.) Habit, I guess probably from the days of cottered cranks. I
always reach for lube when assembling metal bike parts. I've never broken a crank, nor have I had
one loosen during a ride. It's too late for me to change my errant ways.

Steve Shapiro

John Stevenson <[email protected]> wrote in message news:<[email protected]>...
> [email protected] wrote:
>
> > Who are these people!
>
> Marketing.

 

[Tim McTeague]

> Who are these people!
>
> Jobst Brandt [email protected] Palo Alto CA

I just read a news story about the shuttle disaster. It seems that during the investigation into the
last one the folowing information came out. When asked what the odds were of a shuttle catastrophe,
NASA engineers said "1 in 100 launches", NASA managers responded "1 in 10,000"! Seems the tech guys
were about right all along.

In the field of audio, I read an article where an author, writing a review of a power amp, mentioned
that he believed most well made amps sounded the same. The marketing people were furious with him.
When he spoke with the guy who designed the amp, he was not supprised and agreed with the claim. It
seems, the closer he got to the sales dept the more they were conviced of the audible superiority of
their product.

Maybe we should ask the guys who design cranks for their opinion and bypass management altogether.

Tim McTeague