Cause of spalled cones?

Question

Was getting a sort of rubbing sound from my front wheel, like rubbing brakes, but the sound continued even with the bridal loose. So I disassembled my front hub. Everything looked good until I got to the cones. One has a rather noticeable line worn by the balls (more so than I've seen on other bearings), and the other has what I would call a spalled spot in addition to the line, with a rough, wavy area for maybe 15 degrees of arc. The cups, on the other hand, look factory fresh. This is a Shimano RSX hub.

Any idea what would cause this? The hub has 25-30K miles on it, but has been overhauled twice. The sound came up over a period of maybe 100-200 miles riding. I don't go off-road and I don't jump curbs.

Anyway, since the cups look good and the rim probably still has another 10-20K of life left, I'm thinking of getting a new hub and just swapping the cones, vs replacing the hub or buying a new wheel. Any reason not to do this?

More info: I took a closer look at the cones. One is not really that worn -- there's just a barely-perceptible mark from the balls, and I'd not suspect it at all if it weren't for the other cone. The other is spalled to one degree or another all around, however.

And, oddly, the two cones are not identical. The "good" one has the plastic seal washers, while the "bad" one has no groove for seal washers. Clearly, one or the other (probably the "bad" one) has been replaced in one of the two bike shop overhalls.

So the question is, why was the old cone replaced? Presumably it was spalled as well, so what could be causing one cone to spall?

I haven't removed the dust caps, so I can't get a REAL good look at the cups, but will have a shot at it again, using a flashlight. But on my several inspections so far the cups look smooth and shiny. And I'm certain the balls were replaced the last time around. (Unfortunately, inspecting 18 tiny ball bearings is just about impossible.)

Here are pictures:

Unfortunately, my camera only does a middling job with macro photography. In the first shot the bad cone is on the left and the good (stock Shimano) one is on the right. The second shot is the bad cone removed from the axle. The line you can see, up close, looks kind of like a bead of weld, with "puddling" -- little dents kind of pushed up against each other.

When I went to remove the cone I discovered that it was very difficult to remove. Something had snarled the threads on the axle, at about the junction point between the cone and the lock nut. It was impossible to say with any certainty, but it looked like the axle was very slightly bent at that point. It may be that a bent axle was the cause of the failure (though I don't know how it would have gotten bent, or how a bend at that point could cause a bearing failure).

Anyway, swapped in the axle from a new hub (also replaced the balls and repacked it) and the noise seems to be gone (though hard to tell for sure, as it was so windy for my test ride).

Grrr!!!

The noise is back, with the new axle, cones, and balls. Have not taken it apart yet, but I'm guessing one of the cones will be pitted when I do.

And looking for a new wheel, I can't find anything on the internet. It's a Shimano HB-A410 hub, Mavic 622x18 rims, 36 hole. So far I've not found any 36-hole front wheels, and most of the 622 road wheels I find are "aero" -- not exactly the style for my touring bike. I'll check the local shops to see what they can get -- failing that I suppose I'll have to build my own.

"Final answer": Pretty much convinced that the hub was bent and came that way from the factory. This is consistent with the repeated spalling and the damage to the axle that I found. Replaced with a nearly identical wheel from Peter White and things seem fine.

Answer 1

Time traveling here...

If that type of spalling occurs after several thousand miles, then that's most likely normal wear from the little bit of play vs road vibration, etc.

If that occurs within 200 miles, then it means your cone nuts are too tight. Some people here say there should be no play, but that is incorrect. There should be a tiny bit of play in the axle/bearings. If you smack the axle, you should hear it tap lightly.

If you have it too tight, you'll feel very little or zero play, but when you twist the axle by hand, you will feel it grab or catch very slightly. Or, if you hold it by the axle ends and spin the wheel, you'll see it grab periodically (change in friction makes it twist a little in your hands).

That is the minor imperfections in the races and the bearings fighting each other. There should be just a tiny bit more space than the largest imperfection combinations (for a micron or two of grease). That means, most of the spacing will have just a tiny bit of play.

I find that every hub is a little different, but it usually takes 5-10 tweaks to get just the right amount of play when reassembling the wheel bearings/axle/cones/locknuts.

Answer 2

This kind of pitting on the hub cone is usually because there was some small amount of play in the hub.

Play allows sideways movement, which acts like a hammer on the ball bearings as the hub vibrates from being ridden, or hitting bumps on the road.

The other side is normal, with the bearing track. If anything, the extra large compression track in that cone may be why there was a bit of play.

If there is no pitting in the bearing races, replace the cones, readjust the hub, and carry on.

Plan to overhaul and readjust the hubs 500-1000 km of riding after you replace the cones, because the will wear in a bearing track again on the new cones, and the hub will become very slightly loose because of it. It may take 2 or 3 repetitions of this to settle in completely.

Answer 3

I don't wish to be rude but how heavy are you? Back in the 1950s my father owned an Autocycle (that's a heavy duty bicycle with a 98cc or a 50 cc engine) The cups and cones were always giving trouble and he blamed this on the extra weight caused by the engine.

I would suspect that flaking or spalling of the race-ways might be due the lack of preload. Ideally several balls need to be carrying the load at the same time. Extreme Pressure grease might also help, not just thin oil.

Answer 4

Be certain to check on the quality of the grease...... Automobile rear end (differential) lube contains a good percentage of zinc dialkyldithiophosphate--the this lube splashes along the rear axle (rear wheel drive vehicles) and is the only source of lubrication for the rear axle timken tapered roller bearings. It is not unheard of for these bearings to last for over 150,000 miles.

Motor oil, especially racing oils, used high amounts of zinc d in the recent past. (one of its primary functions is to allow metals to slide along each other and to slide along each other, in the absence of an oil film, with none to minimal metal destruction. Zinc has been reduced, as it is destructive to catalytic converters. So, to live with less zinc, most manufacturers have switched to roller cam tappets--as there is less friction than flat tappets. (Flat tappets are probably the highest potential wear point (metal destruction) on an internal combustion engine.

In the oil additive aisle of your auto parts store, look for crankcase additives containing zinc d. Rislone (zinc supplement( is a good brand--this stuff is made specifically for hot-rodders using much higher valve spring pressure on high lift camshafts--regular oil simply isn't going to allow that engine to last--unless it has a higher zinc level.

Use bearing grease with zinc.....and if you aren't certain--use just a few drops on each cone (after you pack in the usual amount of grease) and your cone life will be extended.

Be certain to adjust the bearings properly 1) turn them in--just barely finger tight 2) rotate the wheel on the axle--it probably won't feel smooth and there will probably be a bit of resistance 3) back off just slightly on the cone nut until the wheel seems free on the axle 4) then back off (turn left) the tiniest bit of a turn 5) then lock down both hex nuts 6) check to see that the tiniest bit of slack can be detected--that's what you want....and I do mean tiny.....and I do mean some