Originally Posted by
3alarmer
I'm a little uncertain how the ability to readjust preload at the spindle is going to significantly extend life once those cartridge bearings start to wear ...the races are internal to the cartridge. But I'll take your word for it.
I don't know if external bearings have radial contact or angular contact like cup and cone bearings, but I think the latter because axial preload (as explained in my previous post) takes out any radial slack. With any slack in the bearings, the pedal forces are transmitted from inside race to outside race via only 2 or 3 balls at the bottom of the bearings (on each side) at any given time. With proper preload, that rises to almost 180 degrees of the bottom bearings, or almost half, and this reduces the peak bearing loads greatly, and that prolongs bearing life. Internal cartridge bearings, whether radial contact or angular contact, cannot readjust the preload as they loosen up over time, and that loosening not only affects the bearings, but also can stretch the seals from more radial movement by the inner race, which may let in more contaminents.
The counter to the above issue of peload, is as stated, some feel that internal cartridges may be better off-road, because (my theory) the seals are not right against the crank, such that dirt between might grind the seal.