Discoloured balls?

[scotsbikester]

+1.

You'd be talking many hundreds of degrees to cause such discolouration, which would likely have seen the hub's lubrication boiling.

Also, bearing preload is applied across the entire hub, so it's unlikely that this could cause one side to get hotter than the other.

I reckon it's down to some surface-finish treatment and ultimately not something to worry about. Get it all back together and get back out on the bike

Thanks. As I said up thread, there's a very slight ring on the cones. But nothing like the pitting that's shown in various "how to service your hubs" pictures. I've got new cones on the way anyway. I'll probably replace the existing ones when I'm next working on the bike and it's convenient.

Like I said, I've replaced the balls anyway, because I'd rather have harder chrome steel in there than Shimano's stainless. I used Grade 10 balls.

 

[Hover Fly]

Those copper coloured balls look like they’ve been stained by the grease breaking down.Probably under-lubricated, but over-lubing and wrong sort of grease can do it as well,

 

[rrarider]

I very much doubt that you would be strong enough to heat the bearing balls to over 200 °C and cycle at 10 mph.

 

[wafter]

Thanks. As I said up thread, there's a very slight ring on the cones. But nothing like the pitting that's shown in various "how to service your hubs" pictures. I've got new cones on the way anyway. I'll probably replace the existing ones when I'm next working on the bike and it's convenient.

Like I said, I've replaced the balls anyway, because I'd rather have harder chrome steel in there than Shimano's stainless. I used Grade 10 balls.

Cool - the ring is probably the result of some contamination present; my vintage Routier beater also has some scoring on one of the cones but I've just cleaned & reassembled it with a good dose of moly grease and all's good.. if absolutely reliability's not a concern I'd just get on with using it.

FWIW I'd agree about the alloy steel v. stainless argument, although Shimano are usually very competent. Either way, probably not much worth worrying about (and take that from someone who worries about everything )

 

[gbb]

I very much doubt that you would be strong enough to heat the bearing balls to over 200 °C and cycle at 10 mph.

While accepting i may be wrong...my thoughts exactly.

 

[scotsbikester]

Here then, as promised (?) is a picture of the old cones. One has a lot more "ring" than the other. I can't feel any roughness. I bought new cones (and spacers, locknuts) and installed them. I'll save these. I assume the two cones are the same, they certainly look it. So I guess I'll reuse them if I ever need to, at least the better looking of the two.