kenfreeman096@gmail.com writes:
I'm not sure I get the point about the '30s roadster. It sounds like it had old hardened grease in it, and it was rough possibly because fo dirt, but certainly because balls were running on hardened clumps of grease. That isn't brinelling, if I understand your story. Presumably it could have lead to brinelling, but I guess I really can't say.
That was more to dispute Jobst Brandt's argument about lubrication failure being the cause of denting. That bike had no lubrication left at all, and the headset was totally stiff. I assumed it was in bad shape and probably dented or possibly misaligned, but when I overhauled it, it was shiny smooth on the races, and it adjusted up perfectly smooth when I reassembled it, with no misalignment. One of the nicest pieces of machining I have seen too. Just stiff because the grease now acted like glue. I forgot to mention that it had 28 x 1 3/4 tires and about a 69 degree head angle which supports my ideas that high pressure tires and steeper head angles contribute to denting.
Brinelling isn't really a word of course, but it refers to the Brinell hardness test in which they hammer a surface with a ball bearing and seeing what force is required to dent it. So you can't really call the wear that Jobst Brandt calls fretting, brinelling.
Anyway, I appreciate the comments. I like a lively discussion that presents new ideas. I had actually never heard of the theory of lubrication failure causing the denting, so I looked up Jobst to see if he had weighed in on the subject, which of course he had, and in depth. Jobst presents a good case, and I usually believe what he says, but I am not yet convinced in this case. Too much speculation involved and not enough testing. And my anecdotal experience is hard to ignore.
Bob Freeman
Elliott Bay Bicycles
2116 Western Ave
Seattle, WA 98121
206-441-8144
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