I’ve always been suspicious since he’s called out what looks like brinnelling as “under rotation”.
When he started critiquing welds I really started getting skeptical.
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This popped up in my suggested feed…
I enjoyed that. Summary. The current riders are mostly clean but certain people in past were definitley motor doping…
“Under-rotation” sounds like another way to refer to false-brinelling to me? Not sure what context he was talking about that in.
He had a video about some titanium frame a while ago and his critique on the welds/alignment/fab were way off. I haven’t really watched any of his stuff since then except for this website response video.
Same thing here:
I’m not convinced the bearing is locking up enough to cause this wear.
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Jobst is rolling in his grave: I mean fretting, not brinnelling.
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Yeah, wtf?
That explanation doesn’t make any sense to me.
The end conclusion that bearing misalignment causes the problem is correct. The mechanism being “under-rotation” ie. the inner race spinning on the shaft doesn’t make sense, especially with the wear pattern shown. Fretting would be the mechanism there IMO.
False-Brinelling is fretting, just in the context of the actual bearing race. Brinelling would be impact damage of the balls against the race.
I had one bearing in a cheap BSA30 bb seize after riding in the wet and leaving it sit for a few weeks. The amount of effort required to turn the crank with axle turning inside the inner race was significant. If that was happening intermittently while riding it would be really obvious and the damage would be more significant on the aluminum shaft from galling.
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The wear in that video looks like it only happens on the left side power stroke, not both sides. I suspect the fretting is coming from axial movement, not radial.
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Regardless if cause I feel like that wear pattern is present on the vast majority of 30mm spindle cranks I’ve ever pulled out of a frame.
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If you imagine a shaft going through misaligned bearings like this -/- as the shaft turns the contact points of the inner race on the shaft is going shift from one side to the other with each rotation so that it sort rubs axially. No rotational slip necessary.
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Makes perfect sense.
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The same movement can also make noise, which can be mitigated by greasing the crank axle but then the fretting action displaces the lubricant over time and then it makes noise again.
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He said ‘shaft’!
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He wants to grease your crank shaft
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Has what dentists crave. I think it’s a smart move.
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Make bikes toys again!
lol holy shit are people mad about that on Instagram.
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