Grease on crankshaft splines

[Mojoman]

You can get tubes of copperslip from Midas, around R40 for a small(ish) tube.

[Johan Bornman]

SRAM says grease the splines in their instruction booklet.

 

Campagnolo says degrease square-taper spindles and never grease the bolt.

They say apply Loctite 222 thread sealant on the bolt for ultra-torque cranks.

 

This debate has raged on forums and before that, Usenet for years. I think the Italians got this one wrong.

 

I have two reasons for saying so:

 

1) Most parts such as BB axles are supplied with grease on them. To now remove all the grease is no easy task since a simple wipe won't do it. Even a good wipe with a solvent, usuallsy leaves a one or two molecule layer behind. In the world of grease, a single molecule layer is as good as a thick smearing. The interface can't distinguish. Therefore, only a complete and thorough degreasing will give you a clean surface and this is unlikely to happen and thus most Square Taper cranks are installed effectively greased.

 

Another way to see it is that he only scenario that can be gauranteed is a greased taper and therefore we grease. At least with grease we get a consistent installation position on the taper with a given torque applied to the bold.

 

2) Cranks forced onto square tapers squirm their way up the taper, not down it. If the taper is dry, the crank will have more residual stresses in it to allow it to squirm up than one that is greased. Therefore a dry taper installation has more chance of the crank bolt coming loose during use than one that is greased.

 

You guessed it, my vote is always to grease. However, the debate is moot since ST cranks and even ISIS and Octalink are largely extinct.

[HeartCoppi]

[HeartCoppi]

How do you think that Freddie would ride Darth: Greased or dry?

[HeartCoppi]

My problem with your argument "to grease" is as follows:

 

"deviation:

I have never had problem removing a crank (arm [just to piss you off])

Whether greased or dry they come off. There is never a threat of seizure."

 

In essence a buffer between the surfaces, irrespective whether the thickness is mere microns, is an interruption of perfect fit.

Should the buffer deteriorate or be removed, the presence of the "space" not corrected by re-tightening of the crank bolts will present movement on the taper.

 

Do not grease.

 

The residual stress thing?

[Johan Bornman]

My problem with your argument "to grease" is as follows:

 

"deviation:

I have never had problem removing a crank (arm [just to piss you off])

Whether greased or dry they come off. There is never a threat of seizure."

 

In essence a buffer between the surfaces, irrespective whether the thickness is mere microns, is an interruption of perfect fit.

Should the buffer deteriorate or be removed, the presence of the "space" not corrected by re-tightening of the crank bolts will present movement on the taper.

 

Do not grease.

 

The residual stress thing?

 

The issue is not in removing the crank - that's always easy and forms no part of my argument at all. The interruption of perfect fit is also not an issue. Provided no significant contaminants are at the interface, the alu will shape to fit. This of course requires a forced fit, not your hypothetical perfect fit at zero torque.

 

The issue is getting it to ride far enough up the taper to not allow it to lose contact at the trailing end of the taper when the crank is under extreme torque.

 

Visualise what happens when a square taper crank is put to work.

 

The leading edge of the taper sees an increase in pressure and the trailing edge a decrease. Standing on the crank with the left foot forward sees the reverse. Now, if there are residual stresses in the axial direction (not radial, that's stressed by definition) because of too much friction between alu and steel, this will be relieved in the process described at the beginning of this paragraph.

 

This has the effect that the crank rides higher up the taper. It can't go lower, since the bolt restrains it. As soon as it has ridder up higher and achieved equilibrium, the bolt is loose and can fall out without the crank coming loose.

 

With greasing this scenario is largely eliminated. And as I said, parts are greased at the factory and no-one degreases them completely. Therefore most square tapers are greased by default.

 

Only once Shimano introduced its disastrous Octalink system did the significant elasticity at crank/bb interfaces become evident to observant mechanics.

[FSA]

This debate has raged on forums and before that, Usenet for years. I think the Italians got this one wrong.

 

I have two reasons for saying so:

 

1) Most parts such as BB axles are supplied with grease on them. To now remove all the grease is no easy task since a simple wipe won't do it. Even a good wipe with a solvent, usuallsy leaves a one or two molecule layer behind. In the world of grease, a single molecule layer is as good as a thick smearing. The interface can't distinguish. Therefore, only a complete and thorough degreasing will give you a clean surface and this is unlikely to happen and thus most Square Taper cranks are installed effectively greased.

 

Another way to see it is that he only scenario that can be gauranteed is a greased taper and therefore we grease. At least with grease we get a consistent installation position on the taper with a given torque applied to the bold.

 

2) Cranks forced onto square tapers squirm their way up the taper, not down it. If the taper is dry, the crank will have more residual stresses in it to allow it to squirm up than one that is greased. Therefore a dry taper installation has more chance of the crank bolt coming loose during use than one that is greased.

 

You guessed it, my vote is always to grease. However, the debate is moot since ST cranks and even ISIS and Octalink are largely extinct.

Great Thanks for your input here. Would you say Teflon grease, or copper slip then?

[Johan Bornman]

Great Thanks for your input here. Would you say Teflon grease, or copper slip then?

 

I'll start witih a comment on Teflon grease. It is a foohfee with no application in cycling at all. Any grease is good enough for any application on a bicycle.

 

In this application just about anything from Vaseline through to olive oil will work. And although copper compound is not a lubricant, it will also work. The reason for this is that the lubricity is only required during the actual installation. Thereafter it serves no purpose. The grease needn't have any special properties, be it longevity or extreme pressure or temperature or whatever.