Now, even a good seal cannot keep out water that’s exerting pressure on the seal. So if you’ve driven through hub deep water your bearings should be cleaned and repacked if they’re serviceable. If you have factory sealed ball bearings, you just need to watch for signs of premature failure.

Picture a bearing with balls between the inner and outer surfaces (called races). Traditional bearings use steel balls, either loose between the surfaces or sealed ball within some sort of container. Modern hybrid ceramic sealed ball bearings have ceramic balls inside steel races. Full ceramic bearings have the inner and outer races also in ceramic. The more ceramic components in a bearing, the greater the cost, but there are some advantages.

A look at the XD driver's three-pawl ratchet shows the stiff, flat springs and the unique, three-tooth engagement on each pawl. Threads on the driver (right) engage a sleeve inside the eleven-speed cassette. The driver has two sealed ball bearings. The outboard timken bearing protrudes about four millimeters and indexes the driver into a sleeve beneath the cassette's smallest cogs. 

Front sealed ball bearings, go in from the frint and push it against the first clip. Next part is seal, push in from the inside against the clip, flat part of the seal to the clip..There should be a shoulder or another clip to keep the inner bearing from moving forward and letting the crank web hit the case.  No reason for the seal if good sealed ball bearings are used on the crank..NSK brand with brown rubber seals....Beware of Chinese sealed ball bearings with black rubber seals, they can't hold the case pressure necessary

High quality lithium grease lubricated sealed ball skf bearings use specially tested. This grease can withstand the high temperatures of 120 degrees short time. If a stable working temperature reaches 70 degrees or higher, standard lithium grease life will be shortened.A close-up look at the X-Dome cassette(left) reveals the black-anodized splines of its inner sleeve. The cassette simply spins onto the threads of the XD driver using a Shimano-type freehub lock-ring tool. The XD driver's outboard bearing is visible inside the cassette. In real life, you'll need to install the driver first (right). Slide the XD driver over the axle stub and then turn it counter-clockwise to engage the ratchet. The endcap then snaps onto the axle stub.

Bearing failure analysis, in order to improve the reliability of the work surface important part of systems engineering bearing (bearing functions in the loss of its provisions, resulting in the failure or does not work as a failure of the phenomenon known as (bearing failure can be divided according to their normal life failure and two early failure, which is the main reason for pitting and fatigue leading to early nachi bearing failure analysis and recommend improvements to improve bearing life and reliability.

6879A 

6026MC3

3RT1035