Discoloured balls?

[scotsbikester]

I serviced my front hub, a Shimano M525A. So cup and cone, loose balls.

I completely cleaned it out, including taking the seals out. So had an opportunity to inspect bearing surfaces. Which seemed fine. Except I did notice a very light "ring" around one of them. But no roughness. I thought it was OK.

I used new, Grade10, balls, new grease obviously.

I put the old balls on one side. Today I washed them in white spirit. And noticed exactly half of them are a copper colour:

As this is exactly half of the balls, I assume it's from one side of the hub. Would rust in the hub become ingrained into the balls like that? I think Shimano use stainless balls (I've replaced with chrome steel). The grease was a sort of red colour (as is the grease I've used). So difficult to tell if there was rust in the grease.

These hubs have done 1800 miles over about 4 years.

Annoyingly I can't remember whether the very faint line I saw was on a cup or a cone, and which side. So I'll have to take it apart to clean it up and find out, if I want to order a replacement, if it's (hopefully) a cone.

 

[Cycleops]

As Boris Beckers girlfriend said after he went inside 'new balls please'. Might be safest.
Heat could have that through lack of grease or adjusted too tight.

 

[scotsbikester]

As Boris Beckers girlfriend said after he went inside 'new balls please'. Might be safest.
Heat could have that through lack of grease or adjusted too tight.

Thanks. Yes, as I said, I replaced the balls. Just wondering if there might be other damage.

 

[Big John]

I don't have an answer but I came across exactly the same thing last week at the bike charity where I work. I came to my own conclusion that water must have got into one side of the hub. However, they were only discoloured and not actually corroding and not pitted.

 

[numbnuts]

Heat, looks like they got up to 200c -230c

 

[scotsbikester]

Heat, looks like they got up to 200c -230c

Thanks for the reply. That's a very precise temperature range, is there some sort of, er, thing, that means colour indicates temperature reached.

I'm not sure why that could have happened. I cycle mainly in the north of England and holidays in Scotland. My average speed is 10 mph. Perhaps too tightly adjusted? I've heard that Shimano hubs are sometimes like that new. These are Spa Cycles hand built wheels, so I sort of assumed (maybe incorrectly) that they would adjust the hubs when they build the wheels. Maybe not. They certainly didn't seem to have a great deal of lubricant in.

Anyways, I've put new balls in, Grade 10 chrome steel. And as much grease as I could get in - Silkolene Pro RG2. The general opinion seems to be that that there's no such thing as too much grease.

As I've only just done it, and the tools are to hand, I'll probably strip it again and give the cups and cones a closer inspection, and replace cones if marked.

 

[numbnuts]

Thanks for the reply. That's a very precise temperature range, is there some sort of, er, thing, that means colour indicates temperature reached.

I'm not sure why that could have happened. I cycle mainly in the north of England and holidays in Scotland. My average speed is 10 mph. Perhaps too tightly adjusted? I've heard that Shimano hubs are sometimes like that new. These are Spa Cycles hand built wheels, so I sort of assumed (maybe incorrectly) that they would adjust the hubs when they build the wheels. Maybe not. They certainly didn't seem to have a great deal of lubricant in.

Anyways, I've put new balls in, Grade 10 chrome steel. And as much grease as I could get in - Silkolene Pro RG2. The general opinion seems to be that that there's no such thing as too much grease.

As I've only just done it, and the tools are to hand, I'll probably strip it again and give the cups and cones a closer inspection, and replace cones if marked.

Tempering range of steel, I'm a Blacksmith it's all done by colour

 

[Big John]

If one side of the hub was getting hotter than the other that might account for the discolouration. However, when you adjust a cup and cone hub you usually put the ball bearings in (bedded in grease) followed by the axle with one cone/nut already on the axle. You then tighten the other end after you've put the cone and nut/spacer back on. This I'd have thought would have the effect of applying the same pressure to both sets of bearings, drive and non drive sides. If one set overheats then I'd have thought both sets would overheat and therefore all bearings would show the same extent of discolouration. That said, I still think that heat might still have something to do with it. Maybe one side was less well lubricated than the other.

 

[scotsbikester]

Tempering range of steel, I'm a Blacksmith it's all done by colour

Great, thanks.

 

[scotsbikester]

OK, so I just had a look at the cones. The RHS one had a very faint ring around it. The LHS one a slightly stronger one. I couldn't feel either of them though. I didn't look at the cups, but don't remember seeing any marks/damage when I serviced these bearings, and I did completely clean them out when I did that.

I had fingers covered in grease, my phone was in the top of the house, and it was looking like rain. So I'm afraid I didn't take a photo.
I think the bearings probably have a lot of life in them, especially with the new balls I've just fitted. But I'm a perfectionist, and I wouldn't like the wear on the cones to transfer to the balls, and worse, to the cups.

So I've gone ahead and ordered new cones for both sides. Which was £12 from SJS, and a whole new hub would only cost £20. But still, £8 is £8.

I can only assume the hub was too tight from new (I never checked) and/or short of lube. Hopefully I've corrected that now, and will do again once the new cones arrive. At which point I'll service them again. I'll be mighty miffed if I find the axle is bent!

 

[presta]

Tempering range of steel, I'm a Blacksmith it's all done by colour

That's what I was taught when we used the forge at school, but the film on my polished stainless saucepans goes from blue at the bottom to straw at the top until you tilt them at a different angle, then they go from blue at the top to straw at the bottom. The path difference between the wave reflected by the steel and that reflected by the oxide film, and hence the colour produced by their interference, depends on how long the heat's applied as well as the temperature, and also on the angle at which the light passes through the film.

 

[numbnuts]

That's what I was taught when we used the forge at school, but the film on my polished stainless saucepans goes from blue at the bottom to straw at the top until you tilt them at a different angle, then they go from blue at the top to straw at the bottom. The path difference between the wave reflected by the steel and that reflected by the oxide film, and hence the colour produced by their interference, depends on how long the heat's applied as well as the temperature, and also on the angle at which the light passes through the film.

When I was taught I asked the question “it all depends on how light/dark the workshop was”
reply “Blacksmiths shops are always dark”. It's a fine art and takes years of practice when dealing with hand/machine tools, when dealing with large amounts it's a lot easier with temperature controlled furnaces.

 

[faster]

I don't know what's happened here, but i'd be very surprised if that has been caused by heat.

I just can't see where the energy would come from to create that sort of heat on a bike.

 

[scotsbikester]

As I said, I didn't take a photo of the cones when inspected them. I wish I had. And I didn't look at the cups, because I didn't want to just take out the new balls and grease I'd just applied.

There was a light ring round one cone (LHS), and a very faint ring round the RHS cone. A quick internet search found this:

https://www.instructables.com/Properly-packadjust-bicycle-hub-bearings/

I would say that the ring on my LH cone isn't even as wide as the LH one pictured in "Step 3" there.

I'm thinking that the "wear" I've got isn't at all bad. Though I do have new cones on the way, so I suppose my only decision is how soon to fit them.

Opinions welcome, thanks.

 

[wafter]

I don't know what's happened here, but i'd be very surprised if that has been caused by heat.

I just can't see where the energy would come from to create that sort of heat on a bike.

+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