Bearing polishing
 

Hello all,

I tried to search for this, but there seems to be nothing on it. I would not be surprised if there's a thread on it. So if there is, please let know about it.

I'm wondering what's the latest on polishing bearings and races? Back in the day, before wide spread 24hr internets, things were published in magazines. I found an article on doing this and went through with the directions. It did make an improvement, but I didn't have an exact another set to compare these improvements to. The benefits could have been just cleaning and repacking the bearings.

So with all the internets happening today, this process must have gone to the stratosphere! Or do people just replace their wheels? :fred:

What exactly are you talking about, wheels, headsets?

For wheels, a lot now have cartridge bearings, so it's just a case of popping the old ones out, and replacing with new ones, job done. This is the same for many headsets as well.

If cup and cone, like Shimano, if the cones are pitted, that the end of them, if the bearing are worn, just replace them. If you want real smooth, get Ceramic.

I remember reading (perhaps in Bicycling mag?) one strategy: Disassemble and clean a hub. Put it back together with Simichrome polish instead of grease. Ride it. (Don't remember how far was advised.) Disassemble, clean and put back together with grease. Enjoy!
Never tried it.
That was so long ago, can't remember for sure if the focus was on hubs, or pedals, or bottom brackets.
Never talked with anyone who tried it.

I would advise against spending a lot of time or effort polishing bearings this will do very little to help performance and may actually do more harm than good. Considering the relatively low cost for new high grade bearings I would just buy new ones.

User polishing the bearing races in hubs, headsets, and bottom brackets probably dates from the time when the factory stuff was pretty crude.

Current Shimamo and Campy cup-and-cone hubs are made so well thare is nothing to be gained by the extra effort. Most bottom brackets and headsets and many hubs use cartridge bearings and are pretty well sealed so it isn't even an option.

replacing the bearing balls at overhauls . some softer steel Cups get burnished
as the rougher finished surfaces get worn in..

I was some thing where Aarons Bike repair in Seattle made up a way to grind a new surface
in cones that got pitted , thru not cleaning things often enough.

there was a Drill chucking up a grind stone and another drill motor turning the cone itself on an axle .
to grind the surface equally all the way around..

probably had an assistant trying to cool the piece , water, so as to not lose it's tempering.

The quality of modern bearings and races is such that no polishing is required... if you want things to run a little smoother forget the grease and use oil as many old racers did as it lowers friction and keeps the races flushed.

Mind you, with oil it needs to be refreshed at a fairly continuous rate.

Ceramic bearings offer no practical benefit when used on a bicycle, the improvement they make is so small that a rider will not be able to tell the difference between these and high grade bearings and well machined races.

If there was ever a reason for a rider to polish their bearings and races it was because the products of that time were not as good as they are now or that they could not afford to replace what they had and wanted to eke out a few more miles from their bearings.

The balls actually only make contact on a very narrow track, typically less than 1mm wide. In short order they will wear this to a uniform polish with or without your help. Thereafter the rolling balls keep their track polished better than you could ever hope to.

It's the same principle as railroad tracks, where you'll see rust except for the area where the wheels actually touch. Passing trains keep this part of the rail polished even though it's out in the weather all day.

FBI, I always repack bearing before I sell a bike. The only times I see problems with the bearings the races are bad also. I'm no guru, but it seems as bearings wear, they stay oriented in thier linear placement. Or do they spin randomly? How do you see this?

Whatever out of roundness a ball may see over time, I've never seen it to the extent that i could measure it. I too replace the balls whenever I repack a bearing, but it's more because because I don't want to worry about tracking down balls if I've dropped one. I also make it a (no exception) practice to never introduce a new ball to a used set, which is another reason I start fresh.

As for whether balls wear to a sort of barrel shape, or they stay spherical is of no real interest because, like you, the only observable wear I ever see is the races, not the balls. I suspect that angular contact (happens also in most radial bearings) would have the axis of rotation constantly changing and keep the balls round, but who knows (or cares).

That's exactly what happens. Years ago the technical guru at Bicycling Magazine used to recommend replacing the bearing balls with each overhaul because; "the old ones ovalize with wear and you will never get the clearance adjusted properly." After several years of publishing this myth an Engineer from one of the big bearing manufactures (Timken or SKF) finally wrote to explain that was nonsense as the balls remain round throughout their service life.

One of the beauties of technical mythology, and one reason myths persist is that those who create them are bounded only by their imaginations, have countless possibilities to bring up, and can make stuff seem so interesting or cool. Those who stick with the truth are fenced in tightly have only one single story and that can be so-o-o-o-o boring.

It's analogous to why conspiracy theories abound about anything and everything.

I've used valve-grinding compound on an old set of balls in an old race to clean up pitting in cones. Did it once for a set of nice old pedals and once for a Normandy Luxe Competition hubset, both of which used cones which are essentially unobtanium nowadays. It worked pretty well, and they've stayed in good condition with the light use and obsessive preventative maintenance they've got since then. Started with 220, worked through the grades and finished up with Mother's; cleaned it all off good and installed using new balls.

Your procedure is the right one for salvaging damaged but irreplacable hubs, etc. For modern components it's not necessary or worthwhile.

There is that. There is also that most of us lack the combination of expertise and equipment to run our own tests. I frequently must rely upon people having more expertise than myself in various areas.

Absolutely, and I do likewise. The key is knowing the quality of the sources.

However so many members of the press, and those who post on forums don't. They get their info from secondary sources, who got their information second hand from..... So much of what's published today is circular, repeated form other equally non-qualified sources. And since there are more sources of wrong information than right, and because the first hand sources are often busy doing what they do, and not seeking press, the wrong information circulates farther and faster than the right information.

Add that to the "newsworthy" nature of the wrong info and one needs to have a very good internal filter to avoid getting misled.

I tried the valve grinding compound method once. The new BB was so much smoother than the old one.

I guess if you've got a damaged but irreplacable hub and cone set you could try erzatz polishing methods, and these could work if there's minimal pitting/gouging. A good result will be a crapshoot. Modern bearing surfaces are very hard and milled/ground & polished to exact geometries, using very precise machinery. It is practically impossible to duplicate the precision of these machine tools in your home shop. That being said, I have restored some slightly damaged hubs to acceptable function in my home shop.

Do people understand what the grade number on ball bearings represents ?

Even the lowest grades such as 100 are made to a fairly high tolerances and for them to ovalize to any noticeable degree would require that they be run over more miles than the races could bear.

Corrosion is another issue and is the primary reason why hubs and other bearing assemblies should be overhauled and re-greased and if there is no contamination you probably keep running those bearings through another service cycle.

Funny that some manufacturers warrant their cartridge bearing headsets for 10 years with no specified mileage while a good quality headset that sees regular service could last decades when they were used daily.

I have serviced so many old bicycles that were not garage queens and were daily drivers and in tearing things down found that the stock headset assemblies were fine if the bike had been maintained periodically and most often if the bike had fenders, as it prevents washout.

Will bet the bearings in a 50 year old Raleigh were probably grade 100 which means the variance between the balls in a given lot and size is .0001 inches.

The Japanese Keirin racers are a combination of Velo and horse racing in Japan. To keep everything mechanically equal, with a few exceptions, they still use loose ball hubs, BB and headsets and other old school parts. All the components and frame must be certified for Keirin race use and have an NJS certification stamp. One thing that ties this to the OP is the polished bearing surfaces; all the bearing surfaces have a mirror finish. As an experiment I took an old Campy loose ball hub that still had some pretty smooth bearing surfaces and mixed in some toothpaste 60/40 and then road around that way for about 10 minutes. When I was done I cleaned it all out and was impressed by the shiny surface. It's really not worth the trouble as I'm sure the grease viscosity has a greater effect then the polishing, but it does look really cool.

I'm sure the shiny surface was impressive but it's benefit on bearing efficiency was probably immesurably small.

BTW, what do the Keirin racers use as bearing lube? Track racers often use oil, not grease, because their bikes live in a very clean environment and are reoiled every day they are ridden. The decrease in bearing losses is probably very small but the psychological benefit of knowing you have done everything to reduce them is useful and track races are often won or lost by small fractions of a second so every little benefit is taken.

I've personally disassembled bottom brackets and wheel bearings where the bearings were no longer round. They certainly weren't oval and they were by no means polished - in fact there were chunks of metal missing from some balls.

My impression is that the bearing adjustment and lack of lubrication caused the bearing cage to fragment which then contaminated and destroyed the bearing balls and race. Regardless - the only fix was to replace everything. But I did keep some of that stuff just to use for training purposes so if anyone wants to see some photos, I can take and post some.

Thanks for all the replies regarding this subject. I'm not sure why I'm not getting any notices of replies. I just thought there's no love regarding doing this!

To answer your question, yes I was referring to wheels. I have both a bike that I'm going to be working on from the late 80s and also the bike I'm riding now, which is a Specialized Allez from '08 which I'm looking at in upgrading the bearings.

I kinda thought the bearings/races were very hard and would not lose any material with a polish compound, but no one really did any questioning to this practice at the time. They assumed it was beneficial, and after all, what's the harm? And yeah, as was mentioned, the end result looked rather sexy!

If any one has some rather good links on following and learning to replace the cartridges, please do share. I don't have any sources on tracking down some replacement cartridges either.

Don't waste your money on ceramic. High quality, properly adjusted steel are just as good.

Beat me to it. It might have made sense back in the days of Normandy hubs, but now, not so much.

Many people rag on the low-end Shimano hubs (ex: 'plain' Deore), but if you add some fresh grease, and adjust them properly before putting them into service, they're just fine.

Better tires will make more of a difference than polishing bearings/races.