What about ABEC Ratings?
When all levels of ABEC are made with the same standard of quality, a ball-bearing in an ABEC 5 will spin faster because it has less room to move laterally, thus all it's energy is propelled forward. The unfortunate part is that not all bearings are made to a high standard. It is all a matter of quality. The better bearings are made perfectly round and smooth. The races and bearings in a good skate are honed and polished two or three times. In cheap bearings, the ball-bearings are very rough with many imperfections. There are other factors but it becomes more complicated. Just remember that if you purchase a skate with a good quality bearing you will roll along just fine. To illustrate this, one of the fastest consumer level bearings on the market is the Boss Swiss Bearing which is not even rated. Industry experts say it is probably an ABEC one or three. Racers will often use ABEC 1 bearings in their skates (these would sell for $160 plus).
My mate's bearings spin longer - are they better?
By Duncan Clarke
The simple answer is "Not necessarily". Let me explain.
The difference between spinning the wheel and seeing how long it takes to stop and actually using the bearings during skating is the loading on the bearings. When you are skating, there is a lot of force from all of your weight on those bearings. When you hold the skate up, the only load is the weight of 1 wheel.
Testing how well the bearings perform with no load will not tell you anything about how well they will perform loaded. Try this (or at least think about it):
Build a flat bank that can be made steeper and shallower
Put a pencil on the bank, it's axis perpendicular to the slope
Raise the bank until the pencil rolls down the bank, and note the angle.
Cover a ball-bearing with grease and repeat steps 1 to 3
Which do you think will need the steeper slope? This is the one that would spin longer unloaded. Which do you think would roll better with 80kg on it? That is the one that would make a better bearing.
Basically, the resistance caused by lubricant is unaffected by the load on the bearing. The resistance caused by irregularities in the bearing surface will increase with the load. As such, with no load; lubricant drag is the dominant force whereas with a large load surface quality is dominant.
This is why the spin test is of no use at all in determining how well the bearings will perform when you are skating.