46 mm upright fork. You should know the inner tube outer diameter, metal outer diameter, and bottom case inner dimensions.
Despite not having been serviced in years, it’s this clean. I thought it was a well-balanced modern fork.
It’s natural that the inner tube outer diameter varies considerably from top to bottom. What matters is the sliding surface, but even where the plating has peeled, the dimensions haven’t reduced that much. New tubes can sometimes be thinner than used ones.
There’s almost no oil leak based on outer diameter dimensions. I believe the seal has been damaged for some reason.
Inner tubes are basically not shiny. (Some are shiny, but…)
I suspect the secret is subtle lateral honing-like polishing.
When you wrap a paper wipe around the inner tube in a degreased state and stroke it, the wipe stops at the shiny spots. Those who regularly clean and oil the inner tube are fine, but without lubrication, the seal drags and wears at those spots, or so I imagine.
To avoid wearing down the inner tube and oil seal, we want smooth operation. We use SKF fork seals. When leaks occur with these, it almost always means inner tube replacement.
