Bike greases questions

[it's_a_wonderful_world]

Hello, I have a few questions about the bearing greases article:

I don't understand the format of the DIM label. This image illustrates my confusion:

Where is Mark 2?

Secondly, what does "infrequent access" and "narrow clearances" mean in Table 6, comparing the different solid state lubes?

Thank you for your hard work to crease and maintain such a detailed guide.

 

[BikeGremlin]

Hello, I have a few questions about the bearing greases article:

I don't understand the format of the DIM label. This image illustrates my confusion:
View attachment 128

Where is Mark 2?

Secondly, what does "infrequent access" and "narrow clearances" mean in Table 6, comparing the different solid state lubes?

Thank you for your hard work to crease and maintain such a detailed guide.

Hi Luke,

Very good questions. That's not clearly explained in the tables.

Please let me know if these explanations clarifiy the dilemmas, so that I can add the info to the article (I've already updated the DIN section it with a brief explanation and a link to this discussion).

​

DIN marks​

Mark "2" is used only if a grease has some of the extra qualities listed in that column.

For example, Molybdenum disulphide grease has the solid MoS2 particles, so its DIN mark would contain the letter "F" from the "Mark 2" column, and a typical MoS2 grease's DIN mark would look like this:

DIN KF 2 N-25

Unlike the "Mark 2a," "Mark 2" is obligatory to use and note, if the grease has any of those properties.

Edit:
The low temperature value ("-25") is also not listed in the table, but it is a realistic value for the given grease type and intended application.

"Infrequent access" and "narrow clearances"​

"Infrequent access" refers to places where cleaning and re-greasing regularly is not practical (not affordable or not possible). Some things cost time or money, and generally, the cost of lubrication should not exceed the cost of parts (rough, generalization that is often true and taken into account for maintenance procedures).

Motorcycle suspension linkage pivots are probably a decent (though not perfect) example.

"Narrow clearances" refers to space between two materials whose interface is lubricated. Ball bearings usually have a negative clearance (i.e. preload, they are not loose in the least), but they are rolling and get re-lubricated as they roll (though bicycle headset bearings on a fast descend is a good example of ball bearings not turning nearly enough to get re-lubricated as the vibrations displace the lubricant).

Some other assemblies though do have some (positive) clearance. That clearance can be very tight, very narrow, approaching zero (but not quite). Think various linkages and rods.

Relja

P.S.

For any readers coming here from Google, this is the article we are talking about:
"Bicycle bearing greases – explained"

 

[it's_a_wonderful_world]

Ah, that makes a lot more sense now. I fully understand the DIN labelling system now.

Your definitions of "narrow clearances" and "infrequent access" also make complete sense, but that leads to another question.

As one of the disadvantages of PTFE, you mention that it has a "short life time". This makes sense, but then why would it be the best for infrequent access? Surely the short life time would mean that it needs to be re-lubed more than MoS2?

 

[BikeGremlin]

Ah, that makes a lot more sense now. I fully understand the DIN labelling system now.

Your definitions of "narrow clearances" and "infrequent access" also make complete sense, but that leads to another question.

As one of the disadvantages of PTFE, you mention that it has a "short life time". This makes sense, but then why would it be the best for infrequent access? Surely the short life time would mean that it needs to be re-lubed more than MoS2?

I believe that's my mistake in the section 4.1.2.

Don't know why I wrote it (phrased it) like that.

Technically, PTFE is very stable, long-lasting. It easily shears under load, so it won't last long in high-load applications, but apart from that use-case, it should be a good long-lasting lubrication additive.

For what it's worth, in practice, I only use MoS2 solid-lubricant-additive greases for stuff I can't relubricate very often, like suspension linkage (low-rpm, high-load applications).

PTFE coating is seen in bicycle suspension sliders (wide contact area so no high shear loads, back-forth movement, and kept clean thanks to seals and additional oil and grease lubrication), but I don't use any PTFE greases as such.

I need to double-check and re-write that paragraph.

Relja.

 

[it's_a_wonderful_world]

Thank you for your clarification. I think that paragraph would benefit from being clarified in the article. I will be using MoS2 for these applications thanks to your recommendation, but it is very useful to know the advantages and disadvantages of PTFE and other less used greases, so that I can be certain to avoid them in cases where they would not be the best choice.

Thanks,
Luke