I used to skateboard, we cleaned our bearings all the time. Heres what we always did, made them like new.
1. take out the bearing, be careful not to scratch the center.
2. (only if your bearings have removeable sheilds) take the shields off and clean them
3. Place the bearings in a bath of WD40
4. take the bearings out, let the wd40 drip out, then wipe the down with a rag
5. use TELFON oil only put 1-3 drops in bearing
6. replace bearing into car/truck
(telfon oil can be bought at all sk8board shops, graphite work well also)
