Balls are rated by their grade. A Grade 3 ball means that the ball is 3/1,000,000” tolerance of sphericity, and so is extremely round. In fact, the races of any bearing can't come close to this level of precision in their trueness, but every component being closer to perfect helps decrease friction. Another feature of Grade 3 is surface finish, which in this case is free of scratches or scuffs, and to a <0.003 micron fine finish. The lower the grade number, the better is the ball. Enduro Bearings only uses very high grade balls, whether steel or ceramic. Only 10 years ago, Grade 25 would be considered a very high grade ball, used in the best hubs and bottom brackets made. Enduro Bearings starts with Grade 10 balls and then Grade 5 or Grade 3 at the top.
Silicon Nitride Balls (Si3N4 material)
Made from pure Silicon Nitride material (Si3N4) with extreme high density from uniform compaction (3.25 g/cm3), the micro-structural elements of this material is second to none. In other words, it is extremely dense. There are several materials used for ceramic balls and races and we only use the best, Silicon Nitride. Other ceramic materials should not be considered because of their inferior characteristics. The high precision Grade 3 or 5, Si3N4 pure ceramic balls are 3 or 5/1,000,000” from exactly round in sphericity. 60% lighter weight and 7 times harder than steel, friction is reduced to near zero. Resistance to heat is 8 times greater than that of steel, tougher and less brittle than other ceramic materials. There is simply no comparison for corrosion resistance or magnetic problems with our Si3N4 balls.
A word about ball size:
Remember, increasing the diameter of a sphere by 2 times, increases the surface area by 4 times and the volume by 8 times. Refer to the diagram below for a better visual comparing the ball size of Enduro Bearings bottom bracket bearing to the 3 other competitors for the SAME sized bearing, 24 x 37mm. The red dot on each ball indicates the surface contact area that changes dramatically with the larger balls Enduro Bearings uses.
Further to this, it is easy to understand why we have developed our Angular Contact (A/C) designs for several levels of our bearing line. Compared to radial bearing design, you not only can use larger balls, but since A/C bearings are preloaded, all of the balls are always making contact in the races evenly. In the radial bearing diagram below, you can see how in certain situations for a radial bearing, only half the balls are making contact. And not always in the correct radial axis, since there is internal clearance or play between the balls and races. For A/C bearings, they are always loaded 100% of the time in an opposed 15º direction, carrying the load evenly and smoothly with more contact area. What this means is no wheel “flop” when you change direction on your bike, no rubbing of disc brakes to slow you down, and bearings running smoothly 2 ½ times longer than radial bearings.