Bearing Types

[BenDL]

In a cycling environment it would appear to me that the biggest enemy of a bearing is the moist / dusty / muddy conditions the ebarings are subjected to. So bearing sealing is quite important?

 

As I understand it, the indicators combined with a bearing number, designates the sealing method (e.g. 6805 2RS):

 

2RS - 2 Rubber Seals

ZZ - bearings sealed with aluminium caps - for use in dry areas.

DD - ?? new to me, RS-Components refer to it as double contact seals.

 

Questions -

 

1) Why do bicycle manufacturers use ZZ bearings in their suspension components where it will get wet? Why not 2RS or DD?

2) Anybody have experience with the DD seals? e.g. for Shiamno external hub bearings? Are they worth the additional costs?

3) Enduro bearing claim superiority due to no cages in their bearings & thus more balls fitted. Is the premium cost justified?

4) What grease to use? Is marine grade justified and does it really aid in keeping moisture out of the bearing?

 

Thanks!