Originally Posted by
noglider
Can anyone comment on Shimano's rationale for going with cartridge bearings in BBs but traditional bearings in hubs? I don't disagree, but I'd like to understand it. And what is Shimano making headsets out of these days?
Angular ball bearings are designed for combination radial and axial loading... so I'd guess that Shimano believes that wheel hubs undergo more axial force than a BB. Beyond that, I imagine that it's cheaper to go cup&cone vs an angular cartridge bearing. Other hub manufacturers don't seem to care and just use a standard cartridge (which is a system I'm starting to embrace, since the spare bearings will always be available unlike some of Shimano's older cones which are now unavailable). Actually, I think that having parallel (offset?) cartridge bearings may act in a similar way as an angular cartridge, but I'm not certain without some research.
Originally Posted by
John E
I used to keep a spreadsheet for bicycle maintenance, as I do for the cars, but at least with the cars I have some guidance regarding lubricant and other vital fluid change intervals. I can recommend a good usage-dependent oil change interval for a turbocharged Audi engine with an undersized sump, to avoid the infamous "sludge" problem, but I honestly no good idea how long, in miles and/or in years, bicycle hub grease should hold up.
I think it's different for bikes because they never see the high temps which tend to cause oxidation which breaks grease down... so the limiting factor will be contamination by water or dirt which would vary from one rider to another... hard to give some definitive maintenance schedule for a bicycle bearing.