Bearings sit in the wheel hubs and are what allow the wheels to roll in the skates. Most bearings are rated using the ABEC rating system. The higher the bearing rating, the better the bearing is. The ABEC rating has nothing to do with the bearing quality; it is only a rating system.
ABEC stands for Annular Bearing Engineers Committee. It is not a brand of bearing. This committee works to determine the standards for bearings for the anti-friction bearing manufacturers association. (AFBMA). The ABEC scale classifies different accuracy and tolerance ranges for bearings. There are five ratings in the ABEC scale:
The ABEC rating of a bearing is determined by the following: (for a 608 size bearing)
How close the bore is to 8mm in microns
How close the outer diameter is to 22 in microns
How close the width is to 7mm in microns
The rotating accuracy in microns.
The ABEC rating of a bearing does not affect the speed of your skates, unless you are planning on skating at 330mph. That’s based on a 608 bearing limiting speed of 32,000rpm. Only in extremely high speed applications like ultra high speed motors and precision measuring instruments can bearings above ABEC 1 affect performance. Regardless of how fast you plan to go, speed is affected first and foremost by the choice of lubricant.
As far as tolerances are concerned, the fit of your wheels and axles have a much greater effect on performance than the ABEC rating of your bearings. Wheels and axles for inline skates have extremely loose fits that allow you to press the bearings into the wheel by hand. This masks the benefits of a higher precision bearing by allowing it to slip on the axle or in the wheel. Slippage between the mating parts results in energy lost. Lost Energy is lost speed! How fast you go is up to you and your ability. Higher rated bearings will not make you go faster but you do have more Roll Out. Another way to put this is how long it takes for the wheels to stop spinning, higher rated bearings will spin longer after you stop pushing.
The real qualities of the bearings are the components. Bearings consist of Races, Balls, Cages, and Shields. Chrome steel races are far superior to cheaper carbon steel races and this is the basic difference between good quality bearings for roller skates and cheap imitations. The carbon steel bearings will roll more freely if there is no pressure on them, but after a few times on the skates, they tend to slow the bearings considerably.
There are two common types of lubricant for bearings, grease and oil. Grease is basically oil with a thickener or soap. The thickener acts like a sponge to soak up the oil when not in use. Lubricants keep the metal parts from wearing against one another and dirt away from the sensitive inner workings.
Grease VS. Oil
Prevents Material Wear / Prevents Material Wear
Helps keep dirt out / Can suspend contaminants
Has low torque / Increases torque
Requires little servicing / Requires frequent servicing
Does not last as long / Lasts a long time
From the above you can see that a greased bearing requires little servicing yet cannot run as fast as an oiled bearing. An oiled bearing is susceptible to dust and contamination so it needs to be services more often. As grease is thicker it acts as a seal against dirt, but at the same time it can increase torque and slow down the bearing. A bearing lubricant or cleaner is recommended vs. using any household chemicals to lubricate or clean them. Household cleaners may seem like they are doing the job, but in reality, they are slowing the bearings down.