"Refurbish the wheels"? The actual wheels are made of sophisticated mixes of Polyurethane that usually wear out from use, before they get stale from aging. Old polyurethane is likely to get hard, brittle and less adhesive.
Regarding bearings, my only experience was with inline skates, and the 608 bearing size.
Few 608’s were made to take apart, some didn’t have shields on one side to facilitate easy cleanup in and re-greasing. The best technique is to soak the bearings in a jar full of cleaner, shake jar, remove bearings, wipe down, brush, then spin, soak and shake again. Let them completely dry, and apply new oil/grease at the inner edge of the shield. For speed, use lighter oil, but you need to lube more often, grease last longer and needs to be cleaned less often. Water is death on these bearings, they pit ant rust almost instantly. If they get wet, immediately saturate with WD-40, then clean and lube. Bearings precision is measured on the ABEC rating, usually odd numbers up to a rating of 9. Anything less than 5, simply replace rather than spend time and money cleaning. Precision is the accuracy of the ball and the raceway roundness, or how well machined they are. It does not imply speed of the bearing, many faster spinning bearings we made to be a bit "loose". Meaning that the diameter of the ball was smaller than the raceway, less tight, to facilitate easier less accurate spinning. Tighter bearings are better for machinery that need more precision, like CNC machines.
For many years I was a factory rep for Bauer inline skates, Hyper Wheels, and a few bearing companies.
PS: I am not a Skateboarder, but, I think the truck bushings/bumpers are also polyurethane and would likely harden over time.
Edited 1 time(s). Last edit at 08/24/2021 07:46AM by Ken Sp..