Rusted Shimano R9100P Crank spindle

My bottom bracket bearing was acting up so I took the crankset off. Only to find the spindle on the crankset had markings by the looks of friction from the bearing. Now I’m going to try to see if I am able to get a warranty claim from Shimano, however if I don’t. Has anyone else had similar issues before ? And do advice me on how I can fix it. Thank you

Maybe try sanding it down with some light emerypaper might be able to clean it up.

I was thinking of doing that but the steel is still bare will probably continue to corrode over time.

Sure, you will want to apply some grease at the very least, to protect a bit. You could look for some actual rust prevention covering too.

That looks like galling, not rust. Seems like it was just run too long with a bad bearing and/or improperly set preload.

I’d just keep it well greased, then keep an eye on the condition of the bearings and check the preload from time to time.

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I agree with the others that this looks like galling, I’ve never seen rust on a Shimano axle, what sort of conditions do you ride in?

I would clean that up with Emery cloth and grease the axle before refitting.

It raises further questions, what BB and frame do you have? Does the chainset require any force to fit / remove? If the chainset requires force to fit it could indicate some parallel misalignment which would explain the axle condition (I wonder about this because the drive side bearing landing looks perfect by comparison).

what kind of BB are you running? shimano BBs have a plastic sleeve between the bearing inner race and the crank spindle, such that the crank spindle is never in contact with the hard steel of the bearing.

So I took the bike to the Shimano service center, and surprisingly they have seen quite a few cases of this before. Currently waiting assessment from the warranty department. Anyway usually I run the Dura Ace Press Fit BB86. However I had to go with a different brand a year ago due to stock issues, the BB which was just removed were Wishbone Ceramics.

As for conditions, I currently reside in Malaysia where is hot and humid. When it does rain it really rains hard.

Will be updating the thread once I get more information from the shop.

Had the same thing happen to me, but mine was out of warranty and a dura ace English threaded bb that was cracked.