Originally Posted by
Ghrumpy
Moving metal parts or interfaces generally have a film of protective wax or oil on them to prevent rust in transit. It is not generally intended to be used as a functional lubricant.
While Shimano (unlike Campagnolo) give no explicit instruction to degrease the taper prior to installing the cranks in their tech docs, they do explicitly instruct that grease be used on the threads of their BB cups: "Apply grease to the bottom bracket before installing it." With a pictogram of a little grease tub and an arrow pointing towards the cup threads.
As no such explicit instructions are given for greasing the tapers, I infer that they do not want that.
If, however, a crankset came factory-prepped with grease in the tapers, I would use it. Again, I am open to exceptions when manufacturer-specified.
That's the thing -- the instructions are so specific as to whether to use grease on the cups (ixnay on the plastic ones!) and exactly what torque range to use when installing, that by not saying anything about the tapers, I've wondered if they don't think it matters that much in the long run.
I've read so many well-reasoned arguments in favor of dry or greased tapers over the years that I gave up and decided to shoot for the middle: a very very thin "wetting" of oil or grease on the tapers, torqued to the middle of the specified torque range, checked again after a ride or two, and then that's it. No problems to report like cranks coming loose or "riding up" from this practice, but then I only ride about 3000-5000 miles per year, so it might take a long time to find out if I'm ruining anything.
