Thanks for the help, I figured it out the end caps unscrew.They look like cartridge bearings and now I just have to figure out what size they are.Be careful. I had a Hope hub with sealed bearings. 3 popped out no bother, the 4th twisted round repeatedly so I couldn't just tap it out. No problem, I'll press it out in the vice. I've done this a thousand times with car bearings. Bang. One split hub. I should have cut up the old bearing with a Dremel and removed it in pieces.
That is simplistic: would you care to rephrase? (in the context of BB you mentioned). There will be wear (not caused by water and grit) between the BB inner bearing race and the crankset spindle. Tight tolerances will minimise that wear.the only thing that kills them is they get water and grit in and corrode or seize.
Rephrase? No, not really. Any bearing capable of 30,000 rpm will have such astonishingly tight tolerances and be so hard and wear resistant that when used at bike pedal speeds the wear rate as long as the system remains clean will be infinitesimally slow. Look at something like a car gearbox, it's sealed and all runs in oil. The bearings in it will last for thousands of hours at thousands of rpm without significant wear. Compare and contrast a bike wheel, my MTB being a case in point. 3 of the bearings are still clean and dry, they work perfectly. One got water in, probably because of a failed seal and it's 15+ years old, it has corroded, seized and failed. Cue one dead hub. This is after a few hundred hours use, tops. Many multiples less than our gearbox above. Why? Because water and dirt got in, the mating surfaces corroded, eventually the surfaces became so poor the bearings seized. Nothing to do with the tolerances, normal wear or the speeds used. If that single bearing had not got water and crud in it the wheel would still be in use, I know the others are all still perfect.That is simplistic: would you care to rephrase? (in the context of BB you mentioned). There will be wear (not caused by water and grit) between the BB inner bearing race and the crankset spindle. Tight tolerances will minimise that wear.
No, I still disagree. Bearings in all applications suffer axial forces, that's their job. No study of 4, study of millions. Pedal loading is minuscule compared to most industrial applications where the same bearings suffer thousands of hours at thousands of rpm with heavy loads without incident. Within the context of a BB I maintain the only thing that will kill an industrial bearing running in oil or grease in less than say 100 years is water and dirt.Study of N = 4 then @battered , and not in a BB bearing context (see my text you quoted).
A pair of bearings on either side of a hub do not suffer the cyclical loads that the spindle of a chainset (eg H2) exerts on the external BB bearings. In the context of BBs, it's that set of forces which 'kills' them, not grit and dirt. That's why I suggested that your assertion that " A friend of mine looked up the bearing spec he used for his bottom bracket . . . . the only thing that kills them is they get water and grit in and corrode or seize" was wide of the mark.
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