I understand that as it is the bearings that rotate. Many manuals instruct to put on that thin layer of grease. I do as it does facilitate it going in and out. I was working on a buddies Kawasaki voyager he had just bought. Low miles... 30 year old bike. Came to removing the rear axle and if an axle is stubborn I have an oak dowl rod that I use to persuade it with and it hadnever failed me. Well, that splintered on me and no movement. He was watching me and I grabbed a metal rod and made sure it was a smaller diameter than the axle and beat on it four or five times. Grimacing each time. Finally it popped loose. It was dry and corrosion had basically almost welded it in place. Cleaned it up, lubed it and ever since it slides in and out beautifully. So now I guess I am biased towards lubricant!Technically the "Axles" do not require any grease or lube. There is nothing that actually pivots on them.
It is usually ok to wipe a very thin coating on them, only to prevent any corrosion but is not required.
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