KCNC jockey wheels are excellent, BUT they need to be modified to get the best from them. The top hat/dust cover pair that supports the bearing also allows a certain amount of axial float in the pulley, like the floating guide pulley on all Shimano derailleurs, however, this prevents the dust sheild from doing its job and preventing moisture/dirt from reaching the bearing seal. Trick is to lap/file/machine material from the tophat inner faces, so that the bearing is held correctly by the shoulders of the inner race, and no longer floats. This will allow the dust sheild to do it's thing and the bearing cannot spin on the tophat. Also, generously smear the return on the inside of the D/S with grease to keep water and dirt from contacting the seal.
You must also make sure that the bearing has been fitted centrally in the pulley (flush both sides). None of mine have been right "out of the box".
This has given me excellent bearing life both on and off road, and the elimination of the axial float in the guide pulley gives a really positive shift though it still waits for the ramps. However, as there is no "compensation" your indexing/alignment must always be spot on.
