As the distributors for Enduro bearings, people ask us all the time "what do the bearing codes mean?" or "what does the 2RS stand for?". Well, bearing manufacturers don't simply use these numbers to confuse you, they actually use these numbers to categorise bearings in a way in which from a glance its easy to know what a hearing is typically used for, how robust it is, and if its suited to the application its intended for. Whats even better, is that if used properly, these codes transcend manufacturers, so if you're looking for a bearing and have the standard code it doesn't matter what the make is. Here is a little quick reference guide that explains these bearing codes in detail.
Lets use a 6902 as an example:
S 6902 2RS
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Prefix Code Suffix
(6)902 - This first number relates to the bearing type, typically most bicycle bearings will be a “6” which is a “Deep Groove”. Occasionally you will find a “7” bearing which is a “Single Row Angular Contact”
6(9)02 - This second number relates the bearing series, which reflects the robustness of the bearing. As you go up the scale below from 9 to 4 the inner and outer race thickness will usually increase along with the ball size, this will be to help cope with extra load.
69(02) - The 3rd and 4th digits of the bearing number relate to the bore size of the bearing, numbers 00 to 03 have a designated bore size depending on the number.
*Note: Numbers over 03 simply have a bore size which is 5 times that of the 3rd and 4th digit.