Originally Posted by
El Chaba
Whatever the stated grade of bearing, it pays to know the manufacturer and origin of the bearing. Under no circumstances will I use Chinese bearings in any bike part that I value at all. The quality control is just too poor.
Very true. You can never trust grading of anything coming out of China. Since a good micrometer only measures to .0001", you would be hard put to tell if you were truly getting real grade 25 loose balls and who knows what alloy they would be. To make matters more confusing, bearing assemblies are graded differently than loose balls. From my understanding, bicycle standards are grade 25 loose and grade 5 for assemblies. I don't know how ceramic bearings are rated.