J
Jobst Brandt
Guest
Right from the Shimano web site inder FAQ: http://www.shimano-europe.com/cycling/
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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.
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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
----------------------------------------------------------------------
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