SRAM's choice for the bearing race material is stainless steel. To understand
why stainless is not well suited for for this application, one need only keep in mind one of the main reasons
for using ceramic balls in the first place: superior hardness. Ceramic balls are more than twice as hard as
steel balls. This increase in hardness results in longer bearing life and less ball deflection. The idea of "hybrid"
bearings is to get the best match possible between a ceramic ball and a non-ceramic race. This is why Enduro
Ceramic Hybrid bearings use a specially treated chromium steel (52100) for our races. Here are the hardness numbers
in Rockwell C-Scale:
Ceramic Ball (SI3N4) ............... 75-85 Hardness
Stainless Race ........................ 58-60 Hardness
52100 Race ............................ 62-64 Hardness
While a 2-6 point difference between the stainless and chromium steel may not sound
like a lot, the hardness scale is exponential, and this difference translates into a 15-20% increase in bearing life.
Since one of the main reasons to upgrade bearings is to reduce friction, ball
and race compatibility is critical. The grain structure of stainless steel will not allow it to take as fine a polish
as our treated chromium steel races.
Our jockey wheels weigh in at 9 grams for the top pully and 10 grams for the
lower pulley including our anodized dust covers. The SRAM pulleys come in at 12 grams each.
